Version May 2024
Thioridazine has been shown to prolong the QTc interval in a dose-related manner. Drugs with this potential, including thioridazine, have been associated with torsades de pointes–type arrhythmias and sudden death. Because of its potential for significant, possibly life-threatening, proarrhythmic effects, reserve thioridazine use for the treatment of schizophrenic patients who fail to show an acceptable response to adequate courses of treatment with other antipsychotic drugs, either because of insufficient effectiveness or the inability to achieve an effective dose because of intolerable adverse effects from those drugs.
Elderly patients with dementia-related psychosis treated with antipsychotic drugs are at an increased risk of death. Analyses of 17 placebo-controlled trials (modal duration of 10 weeks), largely in patients taking atypical antipsychotic drugs, revealed a risk of death in drug-treated patients of between 1.6 and 1.7 times the risk of death in placebo-treated patients. Over the course of a typical 10-week controlled trial, the rate of death in drug-treated patients was approximately 4.5% compared with a rate of approximately 2.6% in the placebo group. Although the causes of death were varied, most of the deaths appeared to be either cardiovascular (eg, heart failure, sudden death) or infectious (eg, pneumonia) in nature. Observational studies suggest that, similar to atypical antipsychotic drugs, treatment with conventional antipsychotic drugs may increase mortality. The extent to which the findings of increased mortality in observational studies may be attributed to the antipsychotic drug as opposed to some characteristic(s) of the patients is not clear. Thioridazine is not approved for the treatment of patients with dementia-related psychosis.
Schizophrenia: Oral: Initial: 50 to 100 mg 3 times daily; dosage may be increased at gradual increments based on response and tolerability; usual dosage: 200 to 800 mg/day in 2 to 4 divided doses; maximum: 800 mg/day.
Discontinuation of therapy: In the treatment of chronic psychiatric disease switching therapy rather than discontinuation is generally advised if side effects are intolerable or treatment is not effective. If patient insists on stopping treatment, gradual dose reduction (ie, over several weeks to months) is advised to detect a re-emergence of symptoms and to avoid withdrawal reactions (eg, agitation, alternating feelings of warmth and chill, anxiety, diaphoresis, dyskinesias, GI symptoms, insomnia, irritability, myalgia, paresthesia, psychosis, restlessness, rhinorrhea, tremor, vertigo) unless discontinuation is due to significant adverse effects. Monitor closely to allow for detection of prodromal symptoms of disease recurrence (APA [Keepers 2020]; Lambert 2007; Moncrieff 2020; Post 2020).
Switching antipsychotics: An optimal universal strategy for switching antipsychotic drugs has not been established. Strategies include cross-titration (gradually discontinuing the first antipsychotic while gradually increasing the new antipsychotic) and abrupt change (abruptly discontinuing the first antipsychotic and either increasing the new antipsychotic gradually or starting it at a treatment dose). In patients with schizophrenia at high risk of relapse, the current medication may be maintained at full dose as the new medication is increased (ie, overlap); once the new medication is at therapeutic dose, the first medication is gradually decreased and discontinued over 1 to 2 weeks (Cerovecki 2013; Remington 2005; Takeuchi 2017). Based upon clinical experience, some experts generally prefer cross-titration and overlap approaches rather than abrupt change (Stroup 2022).
Dosage adjustment for concomitant therapy: Significant drug interactions exist, requiring dose/frequency adjustment or avoidance. Consult drug interactions database for more information.
There are no dosage adjustments provided in the manufacturer’s labeling.
There are no dosage adjustments provided in the manufacturer’s labeling; use with caution (hepatic metabolism).
Note: Avoid for behavioral problems associated with dementia or delirium unless alternative nonpharmacologic therapies have failed and patient may harm self or others. If used, consider deprescribing attempts to assess continued need and/or lowest effective dose. Of note, use in certain indications may be appropriate (eg, schizophrenia) (Beers Criteria [AGS 2023]).
Refer to adult dosing. Dosages in the lower range of recommended adult dosing are generally sufficient with late-onset schizophrenia or psychosis. Titrate dosage slowly and monitor carefully (Howard 2000).
(For additional information see "Thioridazine: Pediatric drug information")
Note: In the management of pediatric patients with schizophrenia or severe behavioral problems, use has generally been replaced by second-generation antipsychotics (AACAP [McClellan 2013])
Schizophrenia, refractory: Note: Before initiating treatment with thioridazine, it is strongly recommended that a patient be given at least 2 trials, each with a different antipsychotic drug product, at an adequate dose and for an adequate duration. Dosage should be individualized; use lowest effective dose and shortest effective duration; periodically reassess the need for continued treatment.
Children ≥6 years and Adolescents: Oral: Initial: 0.5 mg/kg/day in 2 to 3 divided doses; maximum initial dose: 50 mg/dose based on adult experience; gradually titrate to clinical response up to a maximum daily dose: 3 mg/kg/day
Dosage adjustment for concomitant therapy: Significant drug interactions exist, requiring dose/frequency adjustment or avoidance. Consult drug interactions database for more information.
There are no dosage adjustments provided in the manufacturer’s labeling.
There are no dosage adjustments provided in the manufacturer’s labeling; use with caution due to hepatic metabolism; accumulation may occur.
The following adverse drug reactions and incidences are derived from product labeling unless otherwise specified. Frequency not defined.
Cardiovascular: ECG changes, hypotension, orthostatic hypotension, peripheral edema, prolonged QT Interval on ECG, torsades de pointes
Central nervous system: Confusion (sundowning), disruption of temperature regulation (Martinez 2002), drowsiness, drug-induced Parkinson disease, extrapyramidal reaction, headache, hyperactive behavior, lethargy, psychotic reaction, restlessness, seizure, tardive dyskinesia (Lehman 2004)
Dermatologic: Dermatitis, hyperpigmentation (Lehman 2004), pallor, skin photosensitivity, skin rash, urticaria
Endocrine & metabolic: Amenorrhea, galactorrhea not associated with childbirth, weight gain (Lehman 2004)
Gastrointestinal: Constipation, diarrhea, nausea, parotid gland enlargement, vomiting, xerostomia
Genitourinary: Breast engorgement, inhibited ejaculation, priapism, sexual difficulty (La Torre 2013), sexual disorder (La Torre 2013)
Hematologic & oncologic: Agranulocytosis, leukopenia
Ophthalmic: Blurred vision, corneal opacity (Lehman 2004), retinitis pigmentosa
Respiratory: Nasal congestion
Severe CNS depression; severe hyper-/hypotensive heart disease; coma; in combination with other drugs that are known to prolong the QTc interval, CYP2D6 inhibitors (fluoxetine, paroxetine), and/or fluvoxamine, propranolol, or pindolol; in patients with congenital long QT syndrome or a history of cardiac arrhythmias; patients known to have genetic defect leading to reduced levels of activity of CYP2D6
Significant drug interactions exist, requiring dose/frequency adjustment or avoidance. Consult drug interactions database for more information.
Concerns related to adverse effects:
• Arrhythmias: [US Boxed Warning]: Has been shown to prolong the QTc interval in a dose-related manner; this may potentially cause torsades de pointes and sudden death. Therefore, thioridazine should be reserved for patients with schizophrenia who have failed to respond to adequate levels of other antipsychotic drugs. Risk of torsades de pointes and/or sudden death may be higher with in patients with bradycardia, hypokalemia, the presence of congenital prolongation of the QTc interval, reduced activity of cytochrome P450 (CYP-450) 2D6, or concomitant use of other drugs that prolong the QTc interval, inhibit CYP2D6, or interfere with the clearance of thioridazine. Consider a cardiac evaluation (including Holter monitoring) in patients who experience symptoms that may be associated with Torsades de Pointes (dizziness, palpitations, syncope). Discontinue therapy in patients with a QTc >500 msec.
• Anticholinergic effects: May cause anticholinergic effects (constipation, xerostomia, blurred vision, urinary retention); use with caution in patients with decreased gastrointestinal motility, paralytic ileus, urinary retention, BPH, xerostomia, or visual problems. Relative to other neuroleptics, thioridazine has a high potency of cholinergic blockade (Richelson 1999).
• Blood dyscrasias: Leukopenia, neutropenia, and/or agranulocytosis (sometimes fatal) have been reported in clinical trials and postmarketing reports with antipsychotic use; presence of risk factors (eg, preexisting low WBC or history of drug-induced leuko-/neutropenia) should prompt periodic blood count assessment. Discontinue therapy at first signs of blood dyscrasias or if absolute neutrophil count <1,000/mm3.
• CNS depression: May cause CNS depression, which may impair physical or mental abilities; patients must be cautioned about performing tasks that require mental alertness (eg, operating machinery, driving).
• Esophageal dysmotility/Aspiration: Antipsychotic use has been associated with esophageal dysmotility and aspiration; risk increases with age. Use with caution in patients at risk for aspiration pneumonia (ie, Alzheimer disease), particularly in patients >75 years (Herzig 2017; Maddalena 2004).
• Extrapyramidal symptoms: May cause extrapyramidal symptoms (EPS), including pseudoparkinsonism, acute dystonic reactions, akathisia, and tardive dyskinesia. Risk of dystonia (and possibly other EPS) may be greater with increased doses, use of conventional antipsychotics, males, and younger patients. Factors associated with greater vulnerability to tardive dyskinesia include older in age, female gender combined with postmenopausal status, Parkinson disease, pseudoparkinsonism symptoms, affective disorders (particularly major depressive disorder), concurrent medical diseases such as diabetes, previous brain damage, alcoholism, poor treatment response, and use of high doses of antipsychotics (APA [Keepers 2020]; Soares-Weiser 2007). Consider therapy discontinuation with signs/symptoms of tardive dyskinesia.
• Falls: May increase the risk for falls due to somnolence, orthostatic hypotension, and motor or sensory instability (Landi 2005; Seppala 2018).
• Hyperprolactinemia: Use associated with increased prolactin levels; clinical significance of hyperprolactinemia in patients with breast cancer or other prolactin-dependent tumors is unknown.
• Neuroleptic malignant syndrome (NMS): May be associated with NMS; monitor for mental status changes, fever, muscle rigidity, and/or autonomic instability. Following recovery from NMS, reintroduction of drug therapy should be carefully considered; if an antipsychotic agent is resumed, monitor closely for NMS.
• Ocular effects: May cause pigmentary retinopathy, characterized by diminution of visual acuity, brownish coloring of vision, and impairment of night vision, in patients exceeding recommended doses. Periodic eye examinations are recommended in patients receiving 600 mg/day or more (Oshika 1995).
• Orthostatic hypotension: May cause orthostatic hypotension; use with caution in patients at risk of this effect or in those who would not tolerate transient hypotensive episodes (cerebrovascular disease, cardiovascular disease, hypovolemia, or concurrent medication use which may predispose to hypotension/bradycardia).
• Temperature regulation: Impaired core body temperature regulation may occur; caution with strenuous exercise, heat exposure, dehydration, and concomitant medication possessing anticholinergic effects (Kwok 2005; Martinez 2002).
Disease-related concerns:
• Cardiovascular disease: Use with caution in patients with severe cardiovascular disease. Do not initiate therapy in patients with a QTc interval >450 msec.
• Dementia: [US Boxed Warning]: Elderly patients with dementia-related psychosis treated with antipsychotics are at an increased risk of death compared to placebo. Most deaths appeared to be either cardiovascular (eg, heart failure, sudden death) or infectious (eg, pneumonia) in nature. Use with caution in patients with Lewy body dementia or Parkinson disease dementia due to greater risk of adverse effects, increased sensitivity to extrapyramidal effects, and association with irreversible cognitive decompensation or death. The APA recommends giving preference to second generation antipsychotics over first generation antipsychotics in elderly patients with dementia-related psychosis due to a potentially greater risk of harm relative to second generation antipsychotics (APA [Reus 2016]). Thioridazine is not approved for the treatment of dementia-related psychosis.
• Hepatic impairment: Use with caution in patients with hepatic impairment.
• Seizure disorder: Use with caution in patients at risk of seizures; first-generation antipsychotics may lower the seizure threshold (APA [Keepers 2020]).
Special populations:
• Older adult: Avoid use; potent anticholinergic agent with potential to cause QT-interval prolongation.
Other warnings/precautions:
• Discontinuation of therapy: When discontinuing antipsychotic therapy, gradually taper antipsychotics to avoid physical withdrawal symptoms and rebound symptoms (APA [Keepers 2020]; WFSBP [Hasan 2012]). Withdrawal symptoms may include agitation, alternating feelings of warmth and cold, anxiety, diaphoresis, dyskinesia, GI symptoms, insomnia, irritability, myalgia, paresthesia, psychosis, restlessness, rhinorrhea, tremor, and vertigo (Lambert 2007; Moncrieff 2020). The risk of withdrawal symptoms is highest following abrupt discontinuation of highly anticholinergic or dopaminergic antipsychotics (Cerovecki 2013). Patients with chronic symptoms, repeated relapses, and clear diagnostic features of schizophrenia are at risk for poor outcomes if medications are discontinued (APA [Keepers 2020]).
Risk of dystonia is increased with the use of high potency and higher doses of conventional antipsychotics and in males and younger patients. Use with caution in children and adolescents; adverse effects due to elevated prolactin levels have been observed; long-term effects on growth or sexual maturation have not been evaluated. Similar to adult experience, the American Academy of Child and Adolescent Psychiatry (AACAP) guidelines recommend gradually tapering antipsychotics to avoid withdrawal symptoms and minimize the risk of relapse (AACAP [McClellan 2007]).
Excipient information presented when available (limited, particularly for generics); consult specific product labeling.
Tablet, Oral, as hydrochloride:
Generic: 10 mg, 25 mg, 50 mg, 100 mg
Yes
Tablets (Thioridazine HCl Oral)
10 mg (per each): $0.54 - $0.60
25 mg (per each): $0.76 - $0.84
50 mg (per each): $0.95 - $1.05
100 mg (per each): $1.09 - $1.19
Disclaimer: A representative AWP (Average Wholesale Price) price or price range is provided as reference price only. A range is provided when more than one manufacturer's AWP price is available and uses the low and high price reported by the manufacturers to determine the range. The pricing data should be used for benchmarking purposes only, and as such should not be used alone to set or adjudicate any prices for reimbursement or purchasing functions or considered to be an exact price for a single product and/or manufacturer. Medi-Span expressly disclaims all warranties of any kind or nature, whether express or implied, and assumes no liability with respect to accuracy of price or price range data published in its solutions. In no event shall Medi-Span be liable for special, indirect, incidental, or consequential damages arising from use of price or price range data. Pricing data is updated monthly.
Oral: Administer with water, food, or milk to decrease GI upset
Schizophrenia: Treatment of patients with schizophrenia who fail to respond adequately to treatment with other antipsychotic drugs, either because of insufficient effectiveness or the inability to achieve an effective dose because of intolerable adverse effects from those medications. Before initiating treatment with thioridazine, it is strongly recommended that a patient be given at least 2 trials, each with a different antipsychotic drug product, at an adequate dose and for an adequate duration.
Thioridazine may be confused with thiothixene, Thorazine
Mellaril may be confused with Elavil, Mebaral
Beers Criteria: Antipsychotics are identified in the Beers Criteria as potentially inappropriate medications to be avoided in patients 65 years and older due to an increased risk of stroke and a greater rate of cognitive decline and mortality in patients with dementia. Evidence also suggests there may be an increased risk of mortality with use independent of dementia. Avoid antipsychotics for behavioral problems associated with dementia or delirium unless alternative nonpharmacologic therapies have failed and patient may harm self or others. In addition, antipsychotics should be used with caution in older adults due to their potential to cause or exacerbate syndrome of inappropriate antidiuretic hormone secretion (SIADH) or hyponatremia; monitor sodium closely with initiation or dosage adjustments in older adults. Use of antipsychotics may be appropriate for FDA approved indications including schizophrenia, bipolar disorder, Parkinson disease psychosis, adjunctive therapy in major depressive disorder, or for short-term use as an antiemetic (Beers Criteria [AGS 2023]).
Substrate of CYP2C19 (minor), CYP2D6 (major); Note: Assignment of Major/Minor substrate status based on clinically relevant drug interaction potential; Inhibits CYP2D6 (moderate); Induces CYP3A4 (weak)
Note: Interacting drugs may not be individually listed below if they are part of a group interaction (eg, individual drugs within “CYP3A4 Inducers [Strong]” are NOT listed). For a complete list of drug interactions by individual drug name and detailed management recommendations, use the Lexicomp drug interactions program by clicking on the “Launch drug interactions program” link above.
Acetylcholinesterase Inhibitors: May diminish the therapeutic effect of Anticholinergic Agents. Anticholinergic Agents may diminish the therapeutic effect of Acetylcholinesterase Inhibitors. Risk C: Monitor therapy
Aclidinium: May enhance the anticholinergic effect of Anticholinergic Agents. Risk X: Avoid combination
Adagrasib: May enhance the QTc-prolonging effect of Thioridazine. Adagrasib may increase the serum concentration of Thioridazine. Risk X: Avoid combination
Agents With Seizure Threshold Lowering Potential: May enhance the adverse/toxic effect of Thioridazine. Specifically, the risk of seizures may be increased. Risk C: Monitor therapy
Alcohol (Ethyl): CNS Depressants may enhance the CNS depressant effect of Alcohol (Ethyl). Risk C: Monitor therapy
Aldesleukin: May increase the serum concentration of CYP Substrates (Narrow Therapeutic Index/Sensitive with Inhibitors). Risk C: Monitor therapy
Alfuzosin: May enhance the hypotensive effect of Blood Pressure Lowering Agents. Risk C: Monitor therapy
Alizapride: May enhance the CNS depressant effect of CNS Depressants. Risk C: Monitor therapy
Amifampridine: Agents With Seizure Threshold Lowering Potential may enhance the neuroexcitatory and/or seizure-potentiating effect of Amifampridine. Risk C: Monitor therapy
Amifostine: Blood Pressure Lowering Agents may enhance the hypotensive effect of Amifostine. Management: When used at chemotherapy doses, hold blood pressure lowering medications for 24 hours before amifostine administration. If blood pressure lowering therapy cannot be held, do not administer amifostine. Use caution with radiotherapy doses of amifostine. Risk D: Consider therapy modification
Aminolevulinic Acid (Systemic): Photosensitizing Agents may enhance the photosensitizing effect of Aminolevulinic Acid (Systemic). Risk X: Avoid combination
Aminolevulinic Acid (Topical): Photosensitizing Agents may enhance the photosensitizing effect of Aminolevulinic Acid (Topical). Risk C: Monitor therapy
Amisulpride (Oral): May enhance the QTc-prolonging effect of QT-prolonging Agents (Moderate Risk). Risk C: Monitor therapy
Amisulpride (Oral): May enhance the hypotensive effect of Hypotension-Associated Agents. Risk C: Monitor therapy
Amisulpride (Oral): Agents With Seizure Threshold Lowering Potential may enhance the adverse/toxic effect of Amisulpride (Oral). Specifically, the risk of seizures may be increased. Risk C: Monitor therapy
Amitriptyline: CYP2D6 Inhibitors (Moderate) may increase serum concentrations of the active metabolite(s) of Amitriptyline. CYP2D6 Inhibitors (Moderate) may increase the serum concentration of Amitriptyline. Risk C: Monitor therapy
Amoxapine: CYP2D6 Inhibitors (Moderate) may increase the serum concentration of Amoxapine. Risk C: Monitor therapy
Antacids: May decrease the absorption of Antipsychotic Agents (Phenothiazines). Risk C: Monitor therapy
Anticholinergic Agents: May enhance the adverse/toxic effect of other Anticholinergic Agents. Risk C: Monitor therapy
Anti-Parkinson Agents (Dopamine Agonist): May diminish the therapeutic effect of Antipsychotic Agents (First Generation [Typical]). Antipsychotic Agents (First Generation [Typical]) may diminish the therapeutic effect of Anti-Parkinson Agents (Dopamine Agonist). Management: Avoid concomitant therapy if possible. If antipsychotic use is necessary, consider using atypical antipsychotics such as clozapine, quetiapine, or ziprasidone at lower initial doses, or a non-dopamine antagonist (eg, pimavanserin). Risk D: Consider therapy modification
Arginine: May enhance the hypotensive effect of Blood Pressure Lowering Agents. Risk C: Monitor therapy
ARIPiprazole: CYP2D6 Inhibitors (Moderate) may increase the serum concentration of ARIPiprazole. Management: Monitor for increased aripiprazole pharmacologic effects. Aripiprazole dose adjustments may or may not be required based on concomitant therapy, indication, or dosage form. Consult full interaction monograph for specific recommendations. Risk C: Monitor therapy
ARIPiprazole: Agents With Seizure Threshold Lowering Potential may enhance the adverse/toxic effect of ARIPiprazole. Specifically, the risk of seizures may be increased. Risk C: Monitor therapy
ARIPiprazole Lauroxil: CYP2D6 Inhibitors (Moderate) may increase serum concentrations of the active metabolite(s) of ARIPiprazole Lauroxil. Risk C: Monitor therapy
ARIPiprazole Lauroxil: Agents With Seizure Threshold Lowering Potential may enhance the adverse/toxic effect of ARIPiprazole Lauroxil. Specifically, the risk of seizures may be increased. Risk C: Monitor therapy
Artemether and Lumefantrine: May increase the serum concentration of CYP2D6 Substrates (High risk with Inhibitors). Risk C: Monitor therapy
Asunaprevir: May increase the serum concentration of Thioridazine. Risk X: Avoid combination
Atogepant: CYP3A4 Inducers (Weak) may decrease the serum concentration of Atogepant. Management: For treatment of episodic migraine, the recommended dose of atogepant is 30 mg once daily or 60 mg once daily when combined with CYP3A4 inducers. When used for treatment of chronic migraine, use of atogepant with CYP3A4 inducers should be avoided. Risk D: Consider therapy modification
Atomoxetine: CYP2D6 Inhibitors (Moderate) may increase the serum concentration of Atomoxetine. Risk C: Monitor therapy
Azelastine (Nasal): May enhance the CNS depressant effect of CNS Depressants. Risk X: Avoid combination
Azithromycin (Systemic): May enhance the QTc-prolonging effect of QT-prolonging Antipsychotics (Moderate Risk). Management: Monitor for QTc interval prolongation and ventricular arrhythmias when these agents are combined. Patients with additional risk factors for QTc prolongation may be at even higher risk. Risk C: Monitor therapy
Barbiturates: May enhance the hypotensive effect of Blood Pressure Lowering Agents. Risk C: Monitor therapy
Benperidol: May enhance the hypotensive effect of Blood Pressure Lowering Agents. Risk C: Monitor therapy
Benperidol: Agents With Seizure Threshold Lowering Potential may enhance the adverse/toxic effect of Benperidol. Specifically, the risk of seizures may be increased. Risk C: Monitor therapy
Beta-Blockers: Antipsychotic Agents (Phenothiazines) may enhance the hypotensive effect of Beta-Blockers. Beta-Blockers may decrease the metabolism of Antipsychotic Agents (Phenothiazines). Antipsychotic Agents (Phenothiazines) may decrease the metabolism of Beta-Blockers. Risk C: Monitor therapy
Blonanserin: CNS Depressants may enhance the CNS depressant effect of Blonanserin. Management: Use caution if coadministering blonanserin and CNS depressants; dose reduction of the other CNS depressant may be required. Strong CNS depressants should not be coadministered with blonanserin. Risk D: Consider therapy modification
Blood Pressure Lowering Agents: May enhance the hypotensive effect of Hypotension-Associated Agents. Risk C: Monitor therapy
Botulinum Toxin-Containing Products: May enhance the anticholinergic effect of Anticholinergic Agents. Risk C: Monitor therapy
Brexanolone: CNS Depressants may enhance the CNS depressant effect of Brexanolone. Risk C: Monitor therapy
Brexpiprazole: CYP2D6 Inhibitors (Moderate) may increase the serum concentration of Brexpiprazole. Management: If brexpiprazole is to be used together with both a moderate CYP2D6 inhibitor and a strong or moderate CYP3A4 inhibitor, the brexpiprazole dose should be reduced to 25% of the usual dose when treating indications other than major depressive disorder. Risk C: Monitor therapy
Brexpiprazole: Agents With Seizure Threshold Lowering Potential may enhance the adverse/toxic effect of Brexpiprazole. Specifically, the risk of seizures may be increased. Risk C: Monitor therapy
Brimonidine (Topical): May enhance the CNS depressant effect of CNS Depressants. Risk C: Monitor therapy
Brimonidine (Topical): May enhance the hypotensive effect of Blood Pressure Lowering Agents. Risk C: Monitor therapy
Bromopride: May enhance the adverse/toxic effect of Antipsychotic Agents. Risk X: Avoid combination
Bromperidol: May diminish the hypotensive effect of Blood Pressure Lowering Agents. Blood Pressure Lowering Agents may enhance the hypotensive effect of Bromperidol. Risk X: Avoid combination
Bromperidol: May enhance the CNS depressant effect of CNS Depressants. Risk X: Avoid combination
Buprenorphine: CNS Depressants may enhance the CNS depressant effect of Buprenorphine. Management: Consider reduced doses of other CNS depressants, and avoiding such drugs in patients at high risk of buprenorphine overuse/self-injection. Initiate buprenorphine at lower doses in patients already receiving CNS depressants. Risk D: Consider therapy modification
Cabergoline: May diminish the therapeutic effect of Antipsychotic Agents. Risk X: Avoid combination
Cannabinoid-Containing Products: Anticholinergic Agents may enhance the tachycardic effect of Cannabinoid-Containing Products. Risk C: Monitor therapy
Cannabinoid-Containing Products: CNS Depressants may enhance the CNS depressant effect of Cannabinoid-Containing Products. Risk C: Monitor therapy
CarBAMazepine: CYP3A4 Inducers (Weak) may decrease the serum concentration of CarBAMazepine. Risk C: Monitor therapy
Cariprazine: Agents With Seizure Threshold Lowering Potential may enhance the adverse/toxic effect of Cariprazine. Specifically, the risk of seizures may be increased. Risk C: Monitor therapy
Carvedilol: CYP2D6 Inhibitors (Moderate) may increase the serum concentration of Carvedilol. Risk C: Monitor therapy
Ceritinib: May enhance the QTc-prolonging effect of QT-prolonging Antipsychotics (Moderate Risk). Management: Monitor for QTc interval prolongation and ventricular arrhythmias when these agents are combined. Patients with additional risk factors for QTc prolongation may be at even higher risk. Risk C: Monitor therapy
Chloral Betaine: May enhance the adverse/toxic effect of Anticholinergic Agents. Risk C: Monitor therapy
Chlormethiazole: May enhance the CNS depressant effect of CNS Depressants. Management: Monitor closely for evidence of excessive CNS depression. The chlormethiazole labeling states that an appropriately reduced dose should be used if such a combination must be used. Risk D: Consider therapy modification
Chlorphenesin Carbamate: May enhance the adverse/toxic effect of CNS Depressants. Risk C: Monitor therapy
Chlorpheniramine: May enhance the arrhythmogenic effect of Thioridazine. Thioridazine may increase the serum concentration of Chlorpheniramine. Management: Avoid this combination when possible. If used, monitor closely for arrhythmia as well as general toxicity of chlorpheniramine. Risk D: Consider therapy modification
Chlorprothixene: Anticholinergic Agents may enhance the anticholinergic effect of Chlorprothixene. Risk C: Monitor therapy
Cimetropium: Anticholinergic Agents may enhance the anticholinergic effect of Cimetropium. Risk X: Avoid combination
Clarithromycin: QT-prolonging Antipsychotics (Moderate Risk) may enhance the QTc-prolonging effect of Clarithromycin. Management: Monitor for QTc interval prolongation and ventricular arrhythmias when these agents are combined. Patients with additional risk factors for QTc prolongation may be at even higher risk. Risk C: Monitor therapy
ClomiPRAMINE: May enhance the QTc-prolonging effect of Thioridazine. Thioridazine may increase serum concentrations of the active metabolite(s) of ClomiPRAMINE. Thioridazine may increase the serum concentration of ClomiPRAMINE. Management: Monitor for QTc interval prolongation and ventricular arrhythmias when these agents are combined. Patients with additional risk factors for QTc prolongation may be at even higher risk. Risk C: Monitor therapy
Clothiapine: Agents With Seizure Threshold Lowering Potential may enhance the adverse/toxic effect of Clothiapine. Specifically, the risk of seizures may be increased. Risk C: Monitor therapy
CloZAPine: Anticholinergic Agents may enhance the constipating effect of CloZAPine. Management: Consider alternatives to this combination whenever possible. If combined, monitor closely for signs and symptoms of gastrointestinal hypomotility and consider prophylactic laxative treatment. Risk D: Consider therapy modification
CNS Depressants: May enhance the adverse/toxic effect of other CNS Depressants. Risk C: Monitor therapy
CYP2D6 Inhibitors (Moderate): May increase the serum concentration of Thioridazine. Risk X: Avoid combination
CYP2D6 Inhibitors (Strong): May increase the serum concentration of Thioridazine. Risk X: Avoid combination
CYP2D6 Inhibitors (Weak): May increase the serum concentration of Thioridazine. Management: Consider avoiding concomitant use of thioridazine and weak CYP2D6 inhibitors. If combined, monitor closely for QTc interval prolongation and arrhythmias. Some weak CYP2D6 inhibitors list use with thioridazine as a contraindication. Risk D: Consider therapy modification
Dapoxetine: May enhance the arrhythmogenic effect of Thioridazine. Dapoxetine may increase the serum concentration of Thioridazine. Risk X: Avoid combination
Daridorexant: May enhance the CNS depressant effect of CNS Depressants. Management: Dose reduction of daridorexant and/or any other CNS depressant may be necessary. Use of daridorexant with alcohol is not recommended, and the use of daridorexant with any other drug to treat insomnia is not recommended. Risk D: Consider therapy modification
Desipramine: CYP2D6 Inhibitors (Moderate) may increase the serum concentration of Desipramine. Risk C: Monitor therapy
Deutetrabenazine: May enhance the adverse/toxic effect of Antipsychotic Agents. Specifically, the risk for akathisia, parkinsonism, or neuroleptic malignant syndrome may be increased. Risk C: Monitor therapy
Deutetrabenazine: CYP2D6 Inhibitors (Moderate) may increase serum concentrations of the active metabolite(s) of Deutetrabenazine. Risk C: Monitor therapy
DexmedeTOMIDine: CNS Depressants may enhance the CNS depressant effect of DexmedeTOMIDine. Management: Monitor for increased CNS depression during coadministration of dexmedetomidine and CNS depressants, and consider dose reductions of either agent to avoid excessive CNS depression. Risk D: Consider therapy modification
Dextromethorphan: CYP2D6 Inhibitors (Moderate) may increase the serum concentration of Dextromethorphan. Risk C: Monitor therapy
Diazoxide: May enhance the hypotensive effect of Blood Pressure Lowering Agents. Risk C: Monitor therapy
Difelikefalin: May enhance the CNS depressant effect of CNS Depressants. Risk C: Monitor therapy
Dimethindene (Topical): May enhance the CNS depressant effect of CNS Depressants. Risk C: Monitor therapy
Domperidone: QT-prolonging Agents (Moderate Risk) may enhance the QTc-prolonging effect of Domperidone. Management: Consider alternatives to this drug combination. If combined, monitor for QTc interval prolongation and ventricular arrhythmias. Patients with additional risk factors for QTc prolongation may be at even higher risk. Risk D: Consider therapy modification
Donepezil: May enhance the neurotoxic (central) effect of Antipsychotic Agents. Risk C: Monitor therapy
DOXOrubicin (Conventional): CYP2D6 Inhibitors (Moderate) may increase the serum concentration of DOXOrubicin (Conventional). Risk X: Avoid combination
Doxylamine: CNS Depressants may enhance the CNS depressant effect of Doxylamine. Risk C: Monitor therapy
Dronedarone: Thioridazine may enhance the QTc-prolonging effect of Dronedarone. Risk X: Avoid combination
DroPERidol: QT-prolonging Antipsychotics (Moderate Risk) may enhance the QTc-prolonging effect of DroPERidol. Management: Monitor for QTc interval prolongation and ventricular arrhythmias when these agents are combined. Patients with additional risk factors for QTc prolongation may be at even higher risk. Risk C: Monitor therapy
DroPERidol: Agents With Seizure Threshold Lowering Potential may enhance the adverse/toxic effect of DroPERidol. Specifically, the risk of seizures may be increased. Risk C: Monitor therapy
Eliglustat: CYP2D6 Inhibitors (Moderate) may increase the serum concentration of Eliglustat. Management: Eliglustat dose is 84 mg daily with CYP2D6 inhibitors. Use is contraindicated (COI) when also combined with strong CYP3A4 inhibitors. When also combined with a moderate CYP3A4 inhibitor, use is COI in CYP2D6 EMs or IMs and should be avoided in CYP2D6 PMs. Risk D: Consider therapy modification
Elranatamab: May increase the serum concentration of CYP Substrates (Narrow Therapeutic Index/Sensitive with Inhibitors). Risk C: Monitor therapy
Eluxadoline: Anticholinergic Agents may enhance the constipating effect of Eluxadoline. Risk X: Avoid combination
Encorafenib: May enhance the QTc-prolonging effect of QT-prolonging Antipsychotics (Moderate Risk). Management: Monitor for QTc interval prolongation and ventricular arrhythmias when these agents are combined. Patients with additional risk factors for QTc prolongation may be at even higher risk. Risk C: Monitor therapy
Epcoritamab: May increase the serum concentration of CYP Substrates (Narrow Therapeutic Index/Sensitive with Inhibitors). Risk C: Monitor therapy
Esketamine: May enhance the CNS depressant effect of CNS Depressants. Risk C: Monitor therapy
Fexinidazole: QT-prolonging Antipsychotics (Moderate Risk) may enhance the QTc-prolonging effect of Fexinidazole. Management: Monitor for QTc interval prolongation and ventricular arrhythmias when these agents are combined. Patients with additional risk factors for QTc prolongation may be at even higher risk. Risk C: Monitor therapy
Flunarizine: CNS Depressants may enhance the CNS depressant effect of Flunarizine. Risk X: Avoid combination
Flunitrazepam: CNS Depressants may enhance the CNS depressant effect of Flunitrazepam. Management: Reduce the dose of CNS depressants when combined with flunitrazepam and monitor patients for evidence of CNS depression (eg, sedation, respiratory depression). Use non-CNS depressant alternatives when available. Risk D: Consider therapy modification
Fluorouracil Products: QT-prolonging Antipsychotics (Moderate Risk) may enhance the QTc-prolonging effect of Fluorouracil Products. Management: Monitor for QTc interval prolongation and ventricular arrhythmias, including torsades de pointes when these agents are combined. Patients with additional risk factors for QTc prolongation may be at even higher risk. Risk C: Monitor therapy
FLUoxetine: May increase the serum concentration of Thioridazine. Risk X: Avoid combination
Flupentixol: QT-prolonging Antipsychotics (Moderate Risk) may enhance the QTc-prolonging effect of Flupentixol. Management: Monitor for QTc interval prolongation and ventricular arrhythmias when these agents are combined. Patients with additional risk factors for QTc prolongation may be at even higher risk. Risk C: Monitor therapy
Flupentixol: Agents With Seizure Threshold Lowering Potential may enhance the adverse/toxic effect of Flupentixol. Specifically, the risk of seizures may be increased. Risk C: Monitor therapy
FluPHENAZine: Agents With Seizure Threshold Lowering Potential may enhance the adverse/toxic effect of FluPHENAZine. Specifically, the risk of seizures may be increased. Risk C: Monitor therapy
FluvoxaMINE: May increase the serum concentration of Thioridazine. Risk X: Avoid combination
Galantamine: May enhance the neurotoxic (central) effect of Antipsychotic Agents. Risk C: Monitor therapy
Gastrointestinal Agents (Prokinetic): Anticholinergic Agents may diminish the therapeutic effect of Gastrointestinal Agents (Prokinetic). Risk C: Monitor therapy
Glofitamab: May increase the serum concentration of CYP Substrates (Narrow Therapeutic Index/Sensitive with Inhibitors). Risk C: Monitor therapy
Glucagon: Anticholinergic Agents may enhance the adverse/toxic effect of Glucagon. Specifically, the risk of gastrointestinal adverse effects may be increased. Risk C: Monitor therapy
Glycopyrrolate (Oral Inhalation): Anticholinergic Agents may enhance the anticholinergic effect of Glycopyrrolate (Oral Inhalation). Risk X: Avoid combination
Glycopyrronium (Topical): May enhance the anticholinergic effect of Anticholinergic Agents. Risk X: Avoid combination
Guanethidine: Antipsychotic Agents may diminish the therapeutic effect of Guanethidine. Risk C: Monitor therapy
Haloperidol: QT-prolonging Antipsychotics (Moderate Risk) may enhance the QTc-prolonging effect of Haloperidol. Management: Monitor for QTc interval prolongation, ventricular arrhythmias, and serotonin syndrome/serotonin toxicity (SS/ST) or NMS when these agents are combined. Patients with additional risk factors for QTc prolongation or SS/ST may be at even higher risk. Risk C: Monitor therapy
Haloperidol: Agents With Seizure Threshold Lowering Potential may enhance the adverse/toxic effect of Haloperidol. Specifically, the risk of seizures may be increased. Risk C: Monitor therapy
Herbal Products with Blood Pressure Lowering Effects: May enhance the hypotensive effect of Blood Pressure Lowering Agents. Risk C: Monitor therapy
Hormonal Contraceptives: CYP3A4 Inducers (Weak) may decrease the serum concentration of Hormonal Contraceptives. Management: Advise patients to use an alternative method of contraception or a back-up method during coadministration, and to continue back-up contraception for 28 days after discontinuing a weak CYP3A4 inducer to ensure contraceptive reliability. Risk D: Consider therapy modification
Huperzine A: May enhance the neurotoxic (central) effect of Antipsychotic Agents. Risk C: Monitor therapy
HydrOXYzine: May enhance the CNS depressant effect of CNS Depressants. Management: Consider a decrease in the CNS depressant dose, as appropriate, when used together with hydroxyzine. Increase monitoring of signs/symptoms of CNS depression in any patient receiving hydroxyzine together with another CNS depressant. Risk D: Consider therapy modification
Hypotension-Associated Agents: Blood Pressure Lowering Agents may enhance the hypotensive effect of Hypotension-Associated Agents. Risk C: Monitor therapy
Iloperidone: CYP2D6 Inhibitors (Moderate) may decrease serum concentrations of the active metabolite(s) of Iloperidone. Specifically, concentrations of the metabolite P95 may be decreased. CYP2D6 Inhibitors (Moderate) may increase serum concentrations of the active metabolite(s) of Iloperidone. Specifically, concentrations of the metabolite P88 may be increased. CYP2D6 Inhibitors (Moderate) may increase the serum concentration of Iloperidone. Risk C: Monitor therapy
Iloperidone: Agents With Seizure Threshold Lowering Potential may enhance the adverse/toxic effect of Iloperidone. Specifically, the risk of seizures may be increased. Risk C: Monitor therapy
Imatinib: May increase the serum concentration of CYP2D6 Substrates (Narrow Therapeutic Index/Sensitive). Risk C: Monitor therapy
Imipramine: May enhance the QTc-prolonging effect of Thioridazine. Thioridazine may increase serum concentrations of the active metabolite(s) of Imipramine. Thioridazine may increase the serum concentration of Imipramine. Management: Monitor for QTc interval prolongation and ventricular arrhythmias when these agents are combined. Patients with additional risk factors for QTc prolongation may be at even higher risk. Risk C: Monitor therapy
Indoramin: CYP2D6 Inhibitors (Moderate) may increase the serum concentration of Indoramin. Risk C: Monitor therapy
Iohexol: Agents With Seizure Threshold Lowering Potential may enhance the adverse/toxic effect of Iohexol. Specifically, the risk for seizures may be increased. Management: Discontinue agents that may lower the seizure threshold 48 hours prior to intrathecal use of iohexol. Wait at least 24 hours after the procedure to resume such agents. In nonelective procedures, consider use of prophylactic antiseizure drugs. Risk D: Consider therapy modification
Iomeprol: Agents With Seizure Threshold Lowering Potential may enhance the adverse/toxic effect of Iomeprol. Specifically, the risk for seizures may be increased. Management: Discontinue agents that may lower the seizure threshold 48 hours prior to intrathecal use of iomeprol. Wait at least 24 hours after the procedure to resume such agents. In nonelective procedures, consider use of prophylactic antiseizure drugs. Risk D: Consider therapy modification
Iopamidol: Agents With Seizure Threshold Lowering Potential may enhance the adverse/toxic effect of Iopamidol. Specifically, the risk for seizures may be increased. Management: Discontinue agents that may lower the seizure threshold 48 hours prior to intrathecal use of iopamidol. Wait at least 24 hours after the procedure to resume such agents. In nonelective procedures, consider use of prophylactic antiseizure drugs. Risk D: Consider therapy modification
Ipratropium (Oral Inhalation): May enhance the anticholinergic effect of Anticholinergic Agents. Risk X: Avoid combination
Itopride: Anticholinergic Agents may diminish the therapeutic effect of Itopride. Risk C: Monitor therapy
Ixabepilone: May enhance the CNS depressant effect of CNS Depressants. Risk C: Monitor therapy
Kava Kava: May enhance the CNS depressant effect of CNS Depressants. Risk C: Monitor therapy
Kratom: May enhance the CNS depressant effect of CNS Depressants. Risk X: Avoid combination
Lemborexant: May enhance the CNS depressant effect of CNS Depressants. Management: Dosage adjustments of lemborexant and of concomitant CNS depressants may be necessary when administered together because of potentially additive CNS depressant effects. Close monitoring for CNS depressant effects is necessary. Risk D: Consider therapy modification
Letermovir: Thioridazine may diminish the therapeutic effect of Letermovir. Risk X: Avoid combination
Levoketoconazole: QT-prolonging Agents (Moderate Risk) may enhance the QTc-prolonging effect of Levoketoconazole. Risk X: Avoid combination
Levosulpiride: Anticholinergic Agents may diminish the therapeutic effect of Levosulpiride. Risk X: Avoid combination
Lithium: May enhance the neurotoxic effect of Antipsychotic Agents. Lithium may decrease the serum concentration of Antipsychotic Agents. Specifically noted with chlorpromazine. Risk C: Monitor therapy
Lofepramine: CYP2D6 Inhibitors (Moderate) may increase serum concentrations of the active metabolite(s) of Lofepramine. The active metabolite of lofepramine is desipramine. Risk C: Monitor therapy
Lormetazepam: May enhance the hypotensive effect of Blood Pressure Lowering Agents. Risk C: Monitor therapy
Loxapine: Agents With Seizure Threshold Lowering Potential may enhance the adverse/toxic effect of Loxapine. Specifically, the risk of seizures may be increased. Risk C: Monitor therapy
Lumateperone: Agents With Seizure Threshold Lowering Potential may enhance the adverse/toxic effect of Lumateperone. Specifically, the risk of seizures may be increased. Risk C: Monitor therapy
Lurasidone: Agents With Seizure Threshold Lowering Potential may enhance the adverse/toxic effect of Lurasidone. Specifically, the risk of seizures may be increased. Risk C: Monitor therapy
Magnesium Sulfate: May enhance the CNS depressant effect of CNS Depressants. Risk C: Monitor therapy
Melatonin: May enhance the adverse/toxic effect of Thioridazine. Risk C: Monitor therapy
Mequitazine: CYP2D6 Inhibitors (Moderate) may increase the serum concentration of Mequitazine. Risk X: Avoid combination
Methotrimeprazine: CNS Depressants may enhance the CNS depressant effect of Methotrimeprazine. Methotrimeprazine may enhance the CNS depressant effect of CNS Depressants. Management: Reduce the usual dose of CNS depressants by 50% if starting methotrimeprazine until the dose of methotrimeprazine is stable. Monitor patient closely for evidence of CNS depression. Risk D: Consider therapy modification
Methoxsalen (Systemic): Photosensitizing Agents may enhance the photosensitizing effect of Methoxsalen (Systemic). Risk C: Monitor therapy
Metoclopramide: May enhance the adverse/toxic effect of Antipsychotic Agents. Risk X: Avoid combination
Metoprolol: CYP2D6 Inhibitors (Moderate) may increase the serum concentration of Metoprolol. Risk C: Monitor therapy
MetyroSINE: May enhance the adverse/toxic effect of Antipsychotic Agents. Specifically, the risk for extrapyramidal symptoms and excessive sedation may be increased. Risk C: Monitor therapy
Mianserin: May enhance the anticholinergic effect of Anticholinergic Agents. Risk C: Monitor therapy
Minocycline (Systemic): May enhance the CNS depressant effect of CNS Depressants. Risk C: Monitor therapy
Molindone: Agents With Seizure Threshold Lowering Potential may enhance the adverse/toxic effect of Molindone. Specifically, the risk of seizures may be increased. Risk C: Monitor therapy
Molsidomine: May enhance the hypotensive effect of Blood Pressure Lowering Agents. Risk C: Monitor therapy
Mosunetuzumab: May increase the serum concentration of CYP Substrates (Narrow Therapeutic Index/Sensitive with Inhibitors). Risk C: Monitor therapy
Nabilone: May enhance the CNS depressant effect of CNS Depressants. Risk X: Avoid combination
Naftopidil: May enhance the hypotensive effect of Blood Pressure Lowering Agents. Risk C: Monitor therapy
Nebivolol: CYP2D6 Inhibitors (Moderate) may increase the serum concentration of Nebivolol. Risk C: Monitor therapy
Nicergoline: May enhance the hypotensive effect of Blood Pressure Lowering Agents. Risk C: Monitor therapy
Nicorandil: May enhance the hypotensive effect of Blood Pressure Lowering Agents. Risk C: Monitor therapy
NiMODipine: CYP3A4 Inducers (Weak) may decrease the serum concentration of NiMODipine. Risk C: Monitor therapy
Nitroglycerin: Anticholinergic Agents may decrease the absorption of Nitroglycerin. Specifically, anticholinergic agents may decrease the dissolution of sublingual nitroglycerin tablets, possibly impairing or slowing nitroglycerin absorption. Risk C: Monitor therapy
Nitroprusside: Blood Pressure Lowering Agents may enhance the hypotensive effect of Nitroprusside. Risk C: Monitor therapy
Nortriptyline: CYP2D6 Inhibitors (Moderate) may increase the serum concentration of Nortriptyline. Risk C: Monitor therapy
Obinutuzumab: May enhance the hypotensive effect of Blood Pressure Lowering Agents. Management: Consider temporarily withholding blood pressure lowering medications beginning 12 hours prior to obinutuzumab infusion and continuing until 1 hour after the end of the infusion. Risk D: Consider therapy modification
OLANZapine: QT-prolonging Antipsychotics (Moderate Risk) may enhance the QTc-prolonging effect of OLANZapine. Management: Monitor for QTc interval prolongation and ventricular arrhythmias when these agents are combined. Patients with additional risk factors for QTc prolongation may be at even higher risk. Risk C: Monitor therapy
OLANZapine: Agents With Seizure Threshold Lowering Potential may enhance the adverse/toxic effect of OLANZapine. Specifically, the risk of seizures may be increased. Risk C: Monitor therapy
Olmutinib: CYP2D6 Inhibitors (Moderate) may increase the serum concentration of Olmutinib. Risk C: Monitor therapy
Olopatadine (Nasal): May enhance the CNS depressant effect of CNS Depressants. Risk X: Avoid combination
Ondansetron: May enhance the QTc-prolonging effect of QT-prolonging Antipsychotics (Moderate Risk). Management: Monitor for QTc interval prolongation, ventricular arrhythmias, including torsades de pointes, when these agents are combined. Patients with additional risk factors for QTc prolongation may be at even higher risk. Risk C: Monitor therapy
Opioid Agonists: CNS Depressants may enhance the CNS depressant effect of Opioid Agonists. Management: Avoid concomitant use of opioid agonists and benzodiazepines or other CNS depressants when possible. These agents should only be combined if alternative treatment options are inadequate. If combined, limit the dosages and duration of each drug. Risk D: Consider therapy modification
Orphenadrine: CNS Depressants may enhance the CNS depressant effect of Orphenadrine. Risk X: Avoid combination
Oxatomide: May enhance the anticholinergic effect of Anticholinergic Agents. Risk X: Avoid combination
Oxomemazine: May enhance the CNS depressant effect of CNS Depressants. Risk X: Avoid combination
Oxybate Salt Products: CNS Depressants may enhance the CNS depressant effect of Oxybate Salt Products. Management: Consider alternatives to this combination when possible. If combined, dose reduction or discontinuation of one or more CNS depressants (including the oxybate salt product) should be considered. Interrupt oxybate salt treatment during short-term opioid use Risk D: Consider therapy modification
OxyCODONE: CNS Depressants may enhance the CNS depressant effect of OxyCODONE. Management: Avoid concomitant use of oxycodone and benzodiazepines or other CNS depressants when possible. These agents should only be combined if alternative treatment options are inadequate. If combined, limit the dosages and duration of each drug. Risk D: Consider therapy modification
Paliperidone: Agents With Seizure Threshold Lowering Potential may enhance the adverse/toxic effect of Paliperidone. Specifically, the risk of seizures may be increased. Risk C: Monitor therapy
Paraldehyde: CNS Depressants may enhance the CNS depressant effect of Paraldehyde. Risk X: Avoid combination
Peginterferon Alfa-2b: May decrease the serum concentration of CYP2D6 Substrates (High risk with Inhibitors). Peginterferon Alfa-2b may increase the serum concentration of CYP2D6 Substrates (High risk with Inhibitors). Risk C: Monitor therapy
Pentamidine (Systemic): May enhance the QTc-prolonging effect of QT-prolonging Antipsychotics (Moderate Risk). Management: Monitor for QTc interval prolongation and ventricular arrhythmias when these agents are combined. Patients with additional risk factors for QTc prolongation may be at even higher risk. Risk C: Monitor therapy
Pentoxifylline: May enhance the hypotensive effect of Blood Pressure Lowering Agents. Risk C: Monitor therapy
Perampanel: May enhance the CNS depressant effect of CNS Depressants. Risk C: Monitor therapy
Periciazine: Agents With Seizure Threshold Lowering Potential may enhance the adverse/toxic effect of Periciazine. Specifically, the risk of seizures may be increased. Risk C: Monitor therapy
Perphenazine: CYP2D6 Inhibitors (Moderate) may increase the serum concentration of Perphenazine. Risk C: Monitor therapy
Perphenazine: Agents With Seizure Threshold Lowering Potential may enhance the adverse/toxic effect of Perphenazine. Specifically, the risk of seizures may be increased. Risk C: Monitor therapy
Pholcodine: Blood Pressure Lowering Agents may enhance the hypotensive effect of Pholcodine. Risk C: Monitor therapy
Phosphodiesterase 5 Inhibitors: May enhance the hypotensive effect of Blood Pressure Lowering Agents. Risk C: Monitor therapy
Pimavanserin: May enhance the QTc-prolonging effect of Thioridazine. Thioridazine may decrease the serum concentration of Pimavanserin. Risk X: Avoid combination
Pimozide: May enhance the QTc-prolonging effect of QT-prolonging Agents (Moderate Risk). Risk X: Avoid combination
Pindolol: Thioridazine may increase the serum concentration of Pindolol. Pindolol may increase the serum concentration of Thioridazine. Risk X: Avoid combination
Pipamperone [INT]: Agents With Seizure Threshold Lowering Potential may enhance the adverse/toxic effect of Pipamperone [INT]. Specifically, the risk of seizures may be increased. Risk C: Monitor therapy
Piribedil: Antipsychotic Agents may diminish the therapeutic effect of Piribedil. Piribedil may diminish the therapeutic effect of Antipsychotic Agents. Management: Use of piribedil with antiemetic neuroleptics is contraindicated, and use with antipsychotic neuroleptics, except for clozapine, is not recommended. Risk X: Avoid combination
Pitolisant: CYP2D6 Inhibitors (Moderate) may increase the serum concentration of Pitolisant. Risk C: Monitor therapy
Polyethylene Glycol-Electrolyte Solution: Agents With Seizure Threshold Lowering Potential may enhance the adverse/toxic effect of Polyethylene Glycol-Electrolyte Solution. Specifically, the risk of seizure may be increased. Risk C: Monitor therapy
Porfimer: Photosensitizing Agents may enhance the photosensitizing effect of Porfimer. Risk C: Monitor therapy
Potassium Chloride: Anticholinergic Agents may enhance the ulcerogenic effect of Potassium Chloride. Management: Patients on drugs with substantial anticholinergic effects should avoid using any solid oral dosage form of potassium chloride. Risk X: Avoid combination
Potassium Citrate: Anticholinergic Agents may enhance the ulcerogenic effect of Potassium Citrate. Management: Patients on drugs with substantial anticholinergic effects should avoid using any solid oral dosage form of potassium citrate. Risk X: Avoid combination
Pramlintide: May enhance the anticholinergic effect of Anticholinergic Agents. These effects are specific to the GI tract. Risk X: Avoid combination
Procarbazine: May enhance the CNS depressant effect of CNS Depressants. Risk C: Monitor therapy
Prochlorperazine: Agents With Seizure Threshold Lowering Potential may enhance the adverse/toxic effect of Prochlorperazine. Specifically, the risk of seizures may be increased. Risk C: Monitor therapy
Promazine: Agents With Seizure Threshold Lowering Potential may enhance the adverse/toxic effect of Promazine. Specifically, the risk of seizures may be increased. Risk C: Monitor therapy
Propofol: QT-prolonging Antipsychotics (Moderate Risk) may enhance the QTc-prolonging effect of Propofol. Management: Monitor for QTc interval prolongation and ventricular arrhythmias when these agents are combined. Patients with additional risk factors for QTc prolongation may be at even higher risk. Risk C: Monitor therapy
Propranolol: May increase the serum concentration of Thioridazine. Thioridazine may increase the serum concentration of Propranolol. Risk X: Avoid combination
Prostacyclin Analogues: May enhance the hypotensive effect of Blood Pressure Lowering Agents. Risk C: Monitor therapy
Protriptyline: CYP2D6 Inhibitors (Moderate) may increase the serum concentration of Protriptyline. Risk C: Monitor therapy
QT-prolonging Agents (Highest Risk): May enhance the QTc-prolonging effect of Thioridazine. Risk X: Avoid combination
QT-prolonging Antidepressants (Moderate Risk): QT-prolonging Antipsychotics (Moderate Risk) may enhance the QTc-prolonging effect of QT-prolonging Antidepressants (Moderate Risk). QT-prolonging Antipsychotics (Moderate Risk) may enhance the serotonergic effect of QT-prolonging Antidepressants (Moderate Risk). This could result in serotonin syndrome. Management: Monitor for QTc interval prolongation, ventricular arrhythmias, and serotonin syndrome/serotonin toxicity (SS/ST) or NMS when these agents are combined. Patients with additional risk factors for QTc prolongation or SS/ST may be at even higher risk. Risk C: Monitor therapy
QT-prolonging Class IC Antiarrhythmics (Moderate Risk): May enhance the QTc-prolonging effect of QT-prolonging Antipsychotics (Moderate Risk). Management: Monitor for QTc interval prolongation and ventricular arrhythmias when these agents are combined. Patients with additional risk factors for QTc prolongation may be at even higher risk. Risk C: Monitor therapy
QT-Prolonging Inhalational Anesthetics (Moderate Risk): May enhance the QTc-prolonging effect of QT-prolonging Antipsychotics (Moderate Risk). Management: Monitor for QTc interval prolongation and ventricular arrhythmias when these agents are combined. Patients with additional risk factors for QTc prolongation may be at even higher risk. Risk C: Monitor therapy
QT-prolonging Kinase Inhibitors (Moderate Risk): QT-prolonging Antipsychotics (Moderate Risk) may enhance the QTc-prolonging effect of QT-prolonging Kinase Inhibitors (Moderate Risk). Management: Monitor for QTc interval prolongation and ventricular arrhythmias when these agents are combined. Patients with additional risk factors for QTc prolongation may be at even higher risk. Risk C: Monitor therapy
QT-prolonging Miscellaneous Agents (Moderate Risk): May enhance the QTc-prolonging effect of QT-prolonging Antipsychotics (Moderate Risk). Management: Monitor for QTc interval prolongation and ventricular arrhythmias when these agents are combined. Patients with additional risk factors for QTc prolongation may be at even higher risk. Risk C: Monitor therapy
QT-prolonging Moderate CYP3A4 Inhibitors (Moderate Risk): May enhance the QTc-prolonging effect of QT-prolonging Antipsychotics (Moderate Risk). Management: Monitor for QTc interval prolongation and ventricular arrhythmias when these agents are combined. Patients with additional risk factors for QTc prolongation may be at even higher risk. Risk C: Monitor therapy
QT-prolonging Quinolone Antibiotics (Moderate Risk): May enhance the QTc-prolonging effect of QT-prolonging Antipsychotics (Moderate Risk). Management: Monitor for QTc interval prolongation and ventricular arrhythmias when these agents are combined. Patients with additional risk factors for QTc prolongation may be at even higher risk. Risk C: Monitor therapy
QUEtiapine: QT-prolonging Antipsychotics (Moderate Risk) may enhance the QTc-prolonging effect of QUEtiapine. Management: Monitor for QTc interval prolongation and ventricular arrhythmias when these agents are combined. Patients with additional risk factors for QTc prolongation may be at even higher risk. Risk C: Monitor therapy
QUEtiapine: Agents With Seizure Threshold Lowering Potential may enhance the adverse/toxic effect of QUEtiapine. Specifically, the risk of seizures may be increased. Risk C: Monitor therapy
Quinagolide: Antipsychotic Agents may diminish the therapeutic effect of Quinagolide. Risk C: Monitor therapy
Quinagolide: May enhance the hypotensive effect of Blood Pressure Lowering Agents. Risk C: Monitor therapy
QuiNIDine: Thioridazine may enhance the QTc-prolonging effect of QuiNIDine. QuiNIDine may increase the serum concentration of Thioridazine. Risk X: Avoid combination
Ramosetron: Anticholinergic Agents may enhance the constipating effect of Ramosetron. Risk C: Monitor therapy
Revefenacin: Anticholinergic Agents may enhance the anticholinergic effect of Revefenacin. Risk X: Avoid combination
RisperiDONE: QT-prolonging Antipsychotics (Moderate Risk) may enhance the QTc-prolonging effect of RisperiDONE. QT-prolonging Antipsychotics (Moderate Risk) may increase the serum concentration of RisperiDONE. Specifically, thioridazine may increase concentrations of risperidone. Management: Monitor for QTc interval prolongation and ventricular arrhythmias when these agents are combined. Patients with additional risk factors for QTc prolongation may be at even higher risk. Risk C: Monitor therapy
RisperiDONE: Agents With Seizure Threshold Lowering Potential may enhance the adverse/toxic effect of RisperiDONE. Specifically, the risk of seizures may be increased. Risk C: Monitor therapy
Rivastigmine: Anticholinergic Agents may diminish the therapeutic effect of Rivastigmine. Rivastigmine may diminish the therapeutic effect of Anticholinergic Agents. Management: Use of rivastigmine with an anticholinergic agent is not recommended unless clinically necessary. If the combination is necessary, monitor for reduced anticholinergic effects. Risk D: Consider therapy modification
Ropeginterferon Alfa-2b: CNS Depressants may enhance the adverse/toxic effect of Ropeginterferon Alfa-2b. Specifically, the risk of neuropsychiatric adverse effects may be increased. Management: Avoid coadministration of ropeginterferon alfa-2b and other CNS depressants. If this combination cannot be avoided, monitor patients for neuropsychiatric adverse effects (eg, depression, suicidal ideation, aggression, mania). Risk D: Consider therapy modification
Rufinamide: May enhance the adverse/toxic effect of CNS Depressants. Specifically, sleepiness and dizziness may be enhanced. Risk C: Monitor therapy
Saquinavir: May enhance the QTc-prolonging effect of Thioridazine. Risk X: Avoid combination
Secretin: Anticholinergic Agents may diminish the therapeutic effect of Secretin. Management: Avoid concomitant use of anticholinergic agents and secretin. Discontinue anticholinergic agents at least 5 half-lives prior to administration of secretin. Risk D: Consider therapy modification
Serotonergic Agents (High Risk): May enhance the adverse/toxic effect of Antipsychotic Agents. Specifically, serotonergic agents may enhance dopamine blockade, possibly increasing the risk for neuroleptic malignant syndrome. Antipsychotic Agents may enhance the serotonergic effect of Serotonergic Agents (High Risk). This could result in serotonin syndrome. Risk C: Monitor therapy
Sertindole: Thioridazine may enhance the QTc-prolonging effect of Sertindole. Thioridazine may increase the serum concentration of Sertindole. Risk X: Avoid combination
Silodosin: May enhance the hypotensive effect of Blood Pressure Lowering Agents. Risk C: Monitor therapy
Sirolimus (Conventional): CYP3A4 Inducers (Weak) may decrease the serum concentration of Sirolimus (Conventional). Risk C: Monitor therapy
Sirolimus (Protein Bound): CYP3A4 Inducers (Weak) may decrease the serum concentration of Sirolimus (Protein Bound). Risk C: Monitor therapy
Sodium Phosphates: Agents With Seizure Threshold Lowering Potential may enhance the adverse/toxic effect of Sodium Phosphates. Specifically, the risk of seizure or loss of consciousness may be increased in patients with significant sodium phosphate-induced fluid or electrolyte abnormalities. Risk C: Monitor therapy
Sulpiride: Antipsychotic Agents may enhance the adverse/toxic effect of Sulpiride. Risk X: Avoid combination
Suvorexant: CNS Depressants may enhance the CNS depressant effect of Suvorexant. Management: Dose reduction of suvorexant and/or any other CNS depressant may be necessary. Use of suvorexant with alcohol is not recommended, and the use of suvorexant with any other drug to treat insomnia is not recommended. Risk D: Consider therapy modification
Tacrolimus (Systemic): CYP3A4 Inducers (Weak) may decrease the serum concentration of Tacrolimus (Systemic). Risk C: Monitor therapy
Talquetamab: May increase the serum concentration of CYP Substrates (Narrow Therapeutic Index/Sensitive with Inhibitors). Risk C: Monitor therapy
Tamoxifen: CYP2D6 Inhibitors (Moderate) may decrease serum concentrations of the active metabolite(s) of Tamoxifen. Specifically, CYP2D6 inhibitors may decrease the metabolic formation of highly potent active metabolites. Management: Consider alternatives to the use of moderate CYP2D6 inhibitors with tamoxifen when possible, as the combination may be associated with reduced clinical effectiveness of tamoxifen. Risk D: Consider therapy modification
Tamsulosin: CYP2D6 Inhibitors (Moderate) may increase the serum concentration of Tamsulosin. Risk C: Monitor therapy
Teclistamab: May increase the serum concentration of CYP Substrates (Narrow Therapeutic Index/Sensitive with Inhibitors). Risk C: Monitor therapy
Tetrabenazine: May enhance the adverse/toxic effect of Antipsychotic Agents. Specifically, the risk for NMS and extrapyramidal symptoms may be increased. Risk C: Monitor therapy
Tetrabenazine: CYP2D6 Inhibitors (Moderate) may increase serum concentrations of the active metabolite(s) of Tetrabenazine. Specifically, concentrations of the active alpha- and beta-dihydrotetrabenazine metabolites may be increased. Risk C: Monitor therapy
Thalidomide: CNS Depressants may enhance the CNS depressant effect of Thalidomide. Risk X: Avoid combination
Thiazide and Thiazide-Like Diuretics: Anticholinergic Agents may increase the serum concentration of Thiazide and Thiazide-Like Diuretics. Risk C: Monitor therapy
Thiopental: Antipsychotic Agents (Phenothiazines) may enhance the adverse/toxic effect of Thiopental. Risk C: Monitor therapy
Thiothixene: Agents With Seizure Threshold Lowering Potential may enhance the adverse/toxic effect of Thiothixene. Specifically, the risk of seizures may be increased. Risk C: Monitor therapy
Timolol (Systemic): CYP2D6 Inhibitors (Moderate) may increase the serum concentration of Timolol (Systemic). Risk C: Monitor therapy
Tiotropium: Anticholinergic Agents may enhance the anticholinergic effect of Tiotropium. Risk X: Avoid combination
Topiramate: Anticholinergic Agents may enhance the adverse/toxic effect of Topiramate. Risk C: Monitor therapy
Trifluoperazine: Agents With Seizure Threshold Lowering Potential may enhance the adverse/toxic effect of Trifluoperazine. Specifically, the risk of seizures may be increased. Risk C: Monitor therapy
Trimeprazine: May enhance the CNS depressant effect of CNS Depressants. Risk C: Monitor therapy
Trimipramine: CYP2D6 Inhibitors (Moderate) may increase the serum concentration of Trimipramine. Risk C: Monitor therapy
Ubrogepant: CYP3A4 Inducers (Weak) may decrease the serum concentration of Ubrogepant. Management: Use an initial ubrogepant dose of 100 mg and second dose (if needed) of 100 mg when used with a weak CYP3A4 inducer. Risk D: Consider therapy modification
Umeclidinium: May enhance the anticholinergic effect of Anticholinergic Agents. Risk X: Avoid combination
Upadacitinib: May increase the serum concentration of CYP2D6 Substrates (Narrow Therapeutic Index/Sensitive). Risk C: Monitor therapy
Valbenazine: CYP2D6 Inhibitors (Moderate) may increase serum concentrations of the active metabolite(s) of Valbenazine. Risk C: Monitor therapy
Valerian: May enhance the CNS depressant effect of CNS Depressants. Risk C: Monitor therapy
Verteporfin: Photosensitizing Agents may enhance the photosensitizing effect of Verteporfin. Risk C: Monitor therapy
Voriconazole: May enhance the QTc-prolonging effect of QT-prolonging Antipsychotics (Moderate Risk). Management: Monitor for QTc interval prolongation and ventricular arrhythmias when these agents are combined. Patients with additional risk factors for QTc prolongation may be at even higher risk. Risk C: Monitor therapy
Vortioxetine: CYP2D6 Inhibitors (Moderate) may increase the serum concentration of Vortioxetine. Risk C: Monitor therapy
Zolpidem: CNS Depressants may enhance the CNS depressant effect of Zolpidem. Management: Reduce the Intermezzo brand sublingual zolpidem adult dose to 1.75 mg for men who are also receiving other CNS depressants. No such dose change is recommended for women. Avoid use with other CNS depressants at bedtime; avoid use with alcohol. Risk D: Consider therapy modification
Zuclopenthixol: CYP2D6 Inhibitors (Moderate) may increase the serum concentration of Zuclopenthixol. Risk C: Monitor therapy
Zuclopenthixol: Agents With Seizure Threshold Lowering Potential may enhance the adverse/toxic effect of Zuclopenthixol. Specifically, the risk of seizures may be increased. Risk C: Monitor therapy
Zuranolone: May enhance the CNS depressant effect of CNS Depressants. Management: Consider alternatives to the use of zuranolone with other CNS depressants or alcohol. If combined, consider a zuranolone dose reduction and monitor patients closely for increased CNS depressant effects. Risk D: Consider therapy modification
Because thioridazine increases prolactin concentrations, amenorrhea in women and impotence in men have been reported. False pregnancy tests may also occur with thioridazine use.
Although outcome information has been published in case reports following maternal use of thioridazine in pregnancy, most information is available for phenothiazines as a class (Erkkola 1983; Heinonen 1977; Scanlan 1972; Slone 1977; Vince 1969). Jaundice or hyper- or hyporeflexia have been reported in newborn infants following maternal use of phenothiazines. Antipsychotic use during the third trimester of pregnancy has a risk for abnormal muscle movements (extrapyramidal symptoms [EPS]) and withdrawal symptoms in newborns following delivery. Symptoms in the newborn may include agitation, feeding disorder, hypertonia, hypotonia, respiratory distress, somnolence, and tremor; these effects may be self-limiting or require hospitalization.
When use in pregnancy is needed, the minimum effective maternal dose should be used to decrease the risk of EPS (ACOG 2008).
It is not known if thioridazine is present in breast milk.
In general, infants exposed to antipsychotic agents should be monitored for signs of adverse events; routine monitoring of infant serum concentrations is not recommended (ACOG 2008).
Mental status; vital signs (as clinically indicated); ECG (baseline, then periodic; do not initiate if QTc >450 msec); weight, height, BMI, waist circumference (baseline; at every visit for the first 6 months; quarterly with stable antipsychotic dose); CBC (as clinically indicated; monitor frequently during the first few months of therapy in patients with preexisting low WBC or history of drug-induced leukopenia/neutropenia); electrolytes (baseline potassium; annually and as clinically indicated); liver function (annually and as clinically indicated); fasting plasma glucose level/HbA1c (baseline, then yearly; in patients with diabetes risk factors or if gaining weight, repeat 4 months after starting antipsychotic, then yearly); lipid panel (baseline; repeat every 2 years if LDL level is normal; repeat every 6 months if LDL level is >130 mg/dL); changes in menstruation, libido, development of galactorrhea, erectile and ejaculatory function (at each visit for the first 12 weeks after the antipsychotic is initiated or until the dose is stable, then yearly); abnormal involuntary movements or parkinsonian signs (baseline; repeat weekly until dose stabilized for at least 2 weeks after introduction and for 2 weeks after any significant dose increase); tardive dyskinesia (every 6 months; high-risk patients every 3 months); visual changes (inquire yearly); ocular examination (yearly in patients >40 years; every 2 years in younger patients) (ADA, 2004; Lehman, 2004; Marder, 2004); fall risk (baseline and periodically during treatment in patients with diseases or on medications that may also increase fall risk) (Landi 2005; Seppala 2018).
Timing of serum samples: Draw trough just before next dose (Hiemke 2018).
Therapeutic reference range: 100 to 200 ng/mL (SI: 270 to 540 nmol/L) (Hiemke 2018). Note: Dosing should be based on therapeutic response as opposed to serum concentrations, however therapeutic drug monitoring can be used to confirm adherence (APA [Keepers 2020]).
Laboratory alert level: 400 ng/mL (SI: 1,080 nmol/L) (Hiemke 2018).
Thioridazine is a piperidine phenothiazine which blocks postsynaptic mesolimbic dopaminergic receptors in the brain; also has activity at serotonin, noradrenaline, and histamine receptors (Fenton, 2007).
Onset of action: Schizophrenia: Initial effects may be observed within 1 to 2 weeks of treatment with continued improvements through 4 to 6 weeks (Agid 2003; Levine 2010).
Absorption: Rapid (Vanderheeren 1977).
Distribution: Vd: 1.8 to 6.7 L/kg (Vanderheeren 1977).
Protein binding: 96% to 99.3% (Cooper 1978).
Metabolism: Hepatic metabolism by sulphoxidation (primarily), demethylation (2%), and hydroxylation (limited); active metabolites mesoridazine and sulphoridazine (Vanderheeren 1977).
Bioavailability: 25% to 33%.
Half-life elimination: 5 to 27 hours (Mårtensson 1973; Muusze 1977; Vanderheeren 1977).
Time to peak, serum: ~1 to 4 hours (Mårtensson 1973).
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