ﺑﺎﺯﮔﺸﺖ ﺑﻪ ﺻﻔﺤﻪ ﻗﺒﻠﯽ
خرید پکیج
تعداد آیتم قابل مشاهده باقیمانده : 3 مورد
نسخه الکترونیک
medimedia.ir

Phentermine: Drug information

Phentermine: Drug information
2024© UpToDate, Inc. and its affiliates and/or licensors. All Rights Reserved.
For additional information see "Phentermine: Patient drug information" and "Phentermine: Pediatric drug information"

For abbreviations, symbols, and age group definitions show table
Brand Names: US
  • Adipex-P;
  • Lomaira
Brand Names: Canada
  • RHO-Phentermine
Pharmacologic Category
  • Anorexiant;
  • Central Nervous System Stimulant;
  • Sympathomimetic
Dosing: Adult
Weight management, short-term

Weight management, short-term (alternative agent):

Note: Avoid in patients with heart disease, poorly controlled hypertension, pulmonary hypertension, or history of substance use disorder (Ref). For short-term use (up to 12 weeks) as an adjunct to diet and exercise in patients who cannot take preferred agents and who have a BMI ≥30 kg/m2 or patients with a BMI ≥27 kg/m2 and ≥1 weight-associated comorbidity (eg, dyslipidemia) (Ref). Some experts use long-term in select patients (Ref). Dosing is presented in terms of the salt, phentermine hydrochloride (not as phentermine base).

Capsule, tablet (excluding Lomaira): Oral: 15 to 18.75 mg once daily or 30 to 37.5 mg in 1 or 2 divided doses (Ref).

Tablet (Lomaira only): Oral: 8 mg 3 times daily 30 minutes before meals.

Dosage adjustment for concomitant therapy: Significant drug interactions exist, requiring dose/frequency adjustment or avoidance. Consult drug interactions database for more information.

Dosing: Kidney Impairment: Adult

Capsule, tablet (excluding Lomaira):

eGFR ≥30 mL/minute/1.73 m2: There are no dosage adjustments provided in the manufacturer's labeling; systemic exposure may be increased; use with caution.

eGFR 15 to 29 mL/minute/1.73 m2: Maximum dose: 15 mg/day.

eGFR <15 mL/minute/1.73 m2: Avoid use (has not been studied).

End-stage renal disease (ESRD) requiring dialysis: Avoid use (has not been studied).

Tablet (Lomaira only): There are no dosage adjustments provided in the manufacturer's labeling (has not been studied); systemic exposure may be increased; use with caution.

Dosing: Hepatic Impairment: Adult

There are no dosage adjustments provided in the manufacturer's labeling (has not been studied).

Dosing: Older Adult

Refer to adult dosing.

Dosing: Pediatric

(For additional information see "Phentermine: Pediatric drug information")

Note: Dosing is presented in terms of phentermine hydrochloride salt, not as phentermine base. Phentermine is available as 2 products (Adipex-P, Lomaira) which have unique dosing.

Weight management, short-term

Weight management, short-term: Note: For short-term use (up to 12 weeks) as an adjunct to diet and exercise in patients who cannot take preferred agents and who have a BMI ≥30 kg/m2 or patients with a BMI ≥27 kg/m2 and ≥1 weight-associated comorbidity (eg, dyslipidemia, diabetes mellitus, hypertension). Dose should be individualized to lowest effective dose.

Adolescents ≥17 years:

Adipex-P: Capsule, tablet: Oral: Usual dose: 37.5 mg once daily before breakfast or 1 to 2 hours after breakfast; with the tablet dosage form, a dose of 18.75 mg (1/2 tablet) once or twice daily may be appropriate in some cases.

Lomaira: Tablet: Oral: 8 mg 3 times daily 30 minutes before meals; in some cases, 4 mg (1/2 tablet) may be appropriate.

Dosage adjustment for concomitant therapy: Significant drug interactions exist, requiring dose/frequency adjustment or avoidance. Consult drug interactions database for more information.

Dosing: Kidney Impairment: Pediatric

Adolescents ≥17 years:

Adipex-P: Capsule, tablet:

eGFR ≥30 mL/minute/1.73 m2: There are no dosage adjustments provided in the manufacturer's labeling; systemic exposure may be increased; use with caution.

eGFR 15 to 29 mL/minute/1.73 m2: Maximum daily dose: 15 mg/day.

eGFR <15 mL/minute/1.73 m2: Avoid use (has not been studied).

End-stage renal disease (ESRD) requiring dialysis: Avoid use (has not been studied).

Lomaira: Tablet: There are no dosage adjustments provided in the manufacturer's labeling (has not been studied); systemic exposure may be increased; use with caution.

Dosing: Hepatic Impairment: Pediatric

Adolescents ≥17 years: There are no dosage adjustments provided in the manufacturer's labeling (has not been studied).

Adverse Reactions (Significant): Considerations
Cardiac effects

Data regarding the cardiac effects of phentermine alone are limited and conflicting; available evidence suggests that cardiac effects are rare (Ref). Phentermine alone may cause increased blood pressure and tachycardia; arrhythmias (including prolonged QT interval on ECG, supraventricular tachycardia, ventricular tachycardia [polymorphic], and ventricular fibrillation); cardiomyopathy (atrial fibrillation-induced); and acute myocardial infarction have been reported in patients with no history of cardiovascular disease (CVD) (Ref). One study suggests that phentermine may not increase blood pressure long-term (Ref). Historically, serious regurgitant valvular heart disease (primarily affecting the mitral, aortic, and/or tricuspid valves) has been reported in patients receiving a combination of phentermine and fenfluramine or dexfenfluramine (combination removed from market) (Ref); rare cases of valvular heart disease with the use of phentermine alone have been reported to the FDA, and the possibility of an association cannot be ruled out. In a descriptive analysis using the FDA Adverse Event Reporting System (FAERS) databases, cardiovascular adverse reactions (unspecified) with phentermine accounted for 31% (n=542) of the total adverse reactions reported among all anti-obesity mediations between 2013 to 2020; the baseline CVD risk of the patients associated with these reports is unknown. In addition, due to limitations related to reporting, these data do not prove cause but rather suggest potential risk (Ref). Conversely, one retrospective study showed no increased risk of incident CVD or death in patients with no history of CVD who were taking phentermine alone for >3 months (Ref).

Mechanism: Not clearly established; possibly due to coronary artery vasospasm related to increased adrenergic activity from phentermine, primarily via norepinephrine (Ref).

CNS effects

Phentermine (alone and in combination) has been associated with CNS effects, including delirium, mania, and psychosis (Ref). Literature has reported insomnia, irritability, and anxiety in 24% to 27% of users (Ref).

Mechanism: Dose-related; related to the pharmacologic action; stimulates release of norepinephrine and dopamine (Ref).

Onset: Varied; typically occurs within 1 week of initiation (Ref) but may occur several months after initiation (Ref).

Risk factors:

• High dose (112.5 to 150 mg/day) (Ref)

• Personal or family history of psychiatric disease (Ref)

Primary pulmonary hypertension

Primary pulmonary hypertension (PPH) has been reported in patients receiving a combination of phentermine and fenfluramine or dexfenfluramine (Ref). The possibility of an association between PPH and the use of phentermine alone cannot be ruled out; at least one case has been reported (Ref).

Mechanism: Time-related; related to the pharmacologic action; hypothesized to be due to an increased 5-HT and subsequent vascular remodeling (Ref).

Onset: Delayed. In a case report with phentermine alone, onset of PPH occurred 3 months after the use of phentermine for 5 weeks (Ref).

Risk factors:

• Duration of use >3 months (Ref)

Adverse Reactions

The following adverse drug reactions are derived from product labeling unless otherwise specified.

Frequency not defined:

Cardiovascular: Increased blood pressure, ischemia, palpitations

Dermatologic: Urticaria

Endocrine & metabolic: Change in libido

Genitourinary: Erectile dysfunction

Nervous system: Dysphoria, euphoria, overstimulation

Postmarketing:

Cardiovascular: Acute myocardial infarction (Prasad 2019), cardiomyopathy (atrial fibrillation-induced) (Kumar 2021), prolonged QT interval on ECG (Kumar 2021), supraventricular tachycardia (Kumar 2021), tachycardia (Yanovski 2014), ventricular fibrillation (Kumar 2021; Tobbia 2012), ventricular tachycardia (polymorphic) (Kumar 2021)

Gastrointestinal: Constipation (Yanovski 2014), diarrhea (Yanovski 2014), gastrointestinal distress (Yanovski 2014), unpleasant taste (Yanovski 2014), xerostomia (Yanovski 2014)

Nervous system: Anxiety (Yanovski 2014), cerebral hemorrhage (McNeil 2018), dizziness (Yanovski 2014), headache (Yanovski 2014), insomnia (Yanovski 2014), irritability (Yanovski 2014), psychosis (Jo 2019), restlessness (Yanovski 2014), tremor (Yanovski 2014)

Renal: Acute interstitial nephritis (Shao 2018)

Respiratory: Primary pulmonary hypertension (Bang 2010)

Contraindications

Hypersensitivity or idiosyncrasy to phentermine, other sympathomimetic amines or any component of the formulation; history of cardiovascular disease (eg, arrhythmias, heart failure, coronary artery disease, stroke, uncontrolled hypertension); hyperthyroidism; glaucoma; agitated states; history of drug abuse; use during or within 14 days following MAO inhibitor therapy; pregnancy; breastfeeding.

Significant drug interactions exist, requiring dose/frequency adjustment or avoidance. Consult drug interactions database for more information.

Warnings/Precautions

Disease-related concerns:

• Cardiovascular disease: Avoid stimulants in patients with known serious structural cardiac abnormalities, cardiomyopathy, serious heart rhythm abnormalities, or other serious cardiac problems that could increase the risk of sudden death that these conditions alone carry. Use with caution in patients with mild hypertension and other cardiovascular conditions that might be exacerbated by increases in blood pressure or heart rate.

• Diabetes: Use with caution in patients with diabetes mellitus; antidiabetic agent requirements (eg, insulin or oral hypoglycemic agents) may be decreased with anorexigens and concomitant dietary restrictions.

• Renal impairment: Use caution in patients with renal impairment; an increase in exposure is expected. Avoid use in patients with eGFR <15 mL/minute/1.73 m2, including end-stage renal disease (ESRD) requiring dialysis (has not been studied).

• Seizure disorders: Avoid or use with caution in patients with history of seizures (Apovian 2015).

• Tourette syndrome: Use with caution in patients with Tourette syndrome; stimulants may unmask tics.

Special populations:

• Older adult: Use caution in this age group due to the risk for causing dependence, hypertension, angina, and myocardial infarction.

Other warnings/precautions:

• Abuse potential: Phentermine is pharmacologically related to the amphetamines, which have a high abuse potential; prolonged use may lead to dependency. Prescriptions should be written for the smallest quantity consistent with good patient care to minimize possibility of overdose.

• Tolerance: Tolerance to the anorectic effect usually develops within a few weeks; discontinue use when tolerance develops, do not exceed recommended dosage in an attempt to overcome tolerance.

Dosage Forms: US

Excipient information presented when available (limited, particularly for generics); consult specific product labeling. [DSC] = Discontinued product

Capsule, Oral, as hydrochloride:

Adipex-P: 37.5 mg [DSC]

Generic: 15 mg, 30 mg, 37.5 mg

Tablet, Oral, as hydrochloride:

Adipex-P: 37.5 mg [scored; contains corn starch]

Adipex-P: 37.5 mg [DSC] [contains corn starch, fd&c blue #1 (brilliant blue)]

Lomaira: 8 mg [scored; contains corn starch, fd&c blue #1 (brilliant blue)]

Generic: 37.5 mg

Generic Equivalent Available: US

Yes

Pricing: US

Capsules (Phentermine HCl Oral)

15 mg (per each): $0.34 - $1.57

30 mg (per each): $0.20 - $1.32

37.5 mg (per each): $0.33 - $1.57

Tablets (Adipex-P Oral)

37.5 mg (per each): $2.53

Tablets (Lomaira Oral)

8 mg (per each): $0.71

Tablets (Phentermine HCl Oral)

37.5 mg (per each): $0.19 - $1.54

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.

Dosage Forms: Canada

Excipient information presented when available (limited, particularly for generics); consult specific product labeling.

Capsule, Oral, as hydrochloride:

Generic: 15 mg, 30 mg

Controlled Substance

C-IV

Administration: Adult

Oral:

Avoid late evening administration. Most effective when combined with a low-calorie diet and behavior modification counseling.

Capsules, tablets (excluding Lomaira): Administer before breakfast or 1 to 2 hours after breakfast. Tablets may be divided in half and dose may be given in 2 divided doses.

Tablet (Lomaira only): Administer 30 minutes before meals. Tablets are scored and may be divided in half.

Administration: Pediatric

Oral: Avoid late evening administration. Scored tablets may be cut in half to achieve dose.

Adipex-P: Administer before breakfast or 1 to 2 hours after breakfast.

Lomaira: Administer 30 minutes before meals.

Use: Labeled Indications

Weight management, short-term: Short-term (few weeks) in a regimen of weight reduction based on exercise, behavioral modification and caloric restriction in the management of exogenous obesity with an initial body mass index ≥30 kg/m2 or ≥27 kg/m2 in the presence of other risk factors (eg, diabetes, hyperlipidemia, controlled hypertension). Note: Some experts use long-term in select patients (ES [Apovian 2015]).

Medication Safety Issues
Sound-alike/look-alike issues:

Phentermine may be confused with phentolamine, phenytoin

High alert medication:

The Institute for Safe Medication Practices (ISMP) includes this medication among its list of drugs (contraindicated in pregnancy) which have a heightened risk of causing significant patient harm when used in error (High-Alert Medications in Community/Ambulatory Care Settings).

International issues:

Fastin [Puerto Rico] may be confused with Fastin dietary supplement [US]

Metabolism/Transport Effects

Substrate of CYP3A4 (minor); Note: Assignment of Major/Minor substrate status based on clinically relevant drug interaction potential

Drug Interactions

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 drug interactions program by clicking on the “Launch drug interactions program” link above.

Acebrophylline: May enhance the stimulatory effect of CNS Stimulants. Risk X: Avoid combination

Alcohol (Ethyl): May enhance the adverse/toxic effect of Phentermine. Risk C: Monitor therapy

Alkalinizing Agents: May decrease the excretion of Amphetamines. Management: Consider alternatives to using amphetamines and alkalinizing agents in combination. If these agents must be used together, patients should be monitored closely for excessive amphetamine effects. Risk D: Consider therapy modification

Amifampridine: Agents With Seizure Threshold Lowering Potential may enhance the neuroexcitatory and/or seizure-potentiating effect of Amifampridine. 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

Ammonium Chloride: May decrease the serum concentration of Amphetamines. This effect is likely due to an enhanced excretion of amphetamines in the urine. Risk C: Monitor therapy

Antihypertensive Agents: Amphetamines may diminish the antihypertensive effect of Antihypertensive Agents. Risk C: Monitor therapy

Antipsychotic Agents: May enhance the adverse/toxic effect of Amphetamines. Antipsychotic Agents may diminish the stimulatory effect of Amphetamines. 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: 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

Asenapine: Agents With Seizure Threshold Lowering Potential may enhance the adverse/toxic effect of Asenapine. Specifically, the risk of seizures may be increased. Risk C: Monitor therapy

Atomoxetine: May enhance the hypertensive effect of Sympathomimetics. Atomoxetine may enhance the tachycardic effect of Sympathomimetics. 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

Blonanserin: Agents With Seizure Threshold Lowering Potential may enhance the adverse/toxic effect of Blonanserin. Specifically, the risk of seizures may be increased. 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

Bromperidol: Agents With Seizure Threshold Lowering Potential may enhance the adverse/toxic effect of Bromperidol. Specifically, the risk of seizures may be increased. Risk C: Monitor therapy

BuPROPion: May enhance the neuroexcitatory and/or seizure-potentiating effect of Agents With Seizure Threshold Lowering Potential. Risk C: Monitor therapy

Cannabinoid-Containing Products: May enhance the tachycardic effect of Sympathomimetics. Risk C: Monitor therapy

Carbonic Anhydrase Inhibitors: May decrease the excretion of Amphetamines. 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

ChlorproMAZINE: Agents With Seizure Threshold Lowering Potential may enhance the adverse/toxic effect of ChlorproMAZINE. Specifically, the risk of seizures may be increased. 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: Agents With Seizure Threshold Lowering Potential may enhance the adverse/toxic effect of CloZAPine. Specifically, the risk of seizures may be increased. Risk C: Monitor therapy

Cocaine (Topical): May enhance the hypertensive effect of Sympathomimetics. Management: Consider alternatives to use of this combination when possible. Monitor closely for substantially increased blood pressure or heart rate and for any evidence of myocardial ischemia with concurrent use. Risk D: Consider therapy modification

CYP2D6 Inhibitors (Moderate): May increase the serum concentration of Amphetamines. Management: Monitor for amphetamine toxicities (including serotonin syndrome) if used with a moderate CYP2D6 inhibitor. Initiate amphetamine therapy at lower doses, monitor frequently, and adjust doses as needed. Discontinue amphetamines if serotoinin syndrome occurs Risk C: Monitor therapy

CYP2D6 Inhibitors (Strong): May increase the serum concentration of Amphetamines. Management: Monitor for amphetamine toxicities (including serotonin syndrome) if used with a strong CYP2D6 inhibitor. Initiate amphetamine therapy at lower doses, monitor frequently, and adjust doses as needed. Discontinue amphetamines if serotoinin syndrome occurs. Risk C: Monitor therapy

Doxofylline: Sympathomimetics may enhance the adverse/toxic effect of Doxofylline. 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

Esketamine: May enhance the hypertensive effect of CNS Stimulants. 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

Gastrointestinal Acidifying Agents: May decrease the serum concentration of Amphetamines. Risk C: Monitor therapy

Guanethidine: May enhance the arrhythmogenic effect of Sympathomimetics. Guanethidine may enhance the hypertensive effect of Sympathomimetics. 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

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

Iobenguane Radiopharmaceutical Products: Amphetamines may diminish the therapeutic effect of Iobenguane Radiopharmaceutical Products. Management: Discontinue all drugs that may inhibit or interfere with catecholamine transport or uptake for at least 5 biological half-lives before iobenguane administration. Do not administer these drugs until at least 7 days after each iobenguane dose. Risk X: Avoid combination

Iobenguane Radiopharmaceutical Products: CNS Stimulants may diminish the therapeutic effect of Iobenguane Radiopharmaceutical Products. Management: Discontinue all drugs that may inhibit or interfere with catecholamine transport or uptake for at least 5 biological half-lives before iobenguane administration. Do not administer these drugs until at least 7 days after each iobenguane dose. Risk X: Avoid combination

Ioflupane I 123: Phentermine may diminish the diagnostic effect of Ioflupane I 123. 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

Kratom: May enhance the adverse/toxic effect of Sympathomimetics. Risk X: Avoid combination

Levothyroxine: May enhance the adverse/toxic effect of Sympathomimetics. Specifically, the risk of coronary insufficiency may be increased in patients with coronary artery disease. Levothyroxine may enhance the therapeutic effect of Sympathomimetics. Sympathomimetics may enhance the therapeutic effect of Levothyroxine. 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

Methenamine: May decrease the serum concentration of Amphetamines. This effect is likely due to an enhanced excretion of amphetamines in the urine. Risk C: Monitor therapy

Methotrimeprazine: Agents With Seizure Threshold Lowering Potential may enhance the adverse/toxic effect of Methotrimeprazine. Specifically, the risk of seizures may be increased. 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

Monoamine Oxidase Inhibitors: May enhance the hypertensive effect of Amphetamines. While linezolid and tedizolid may interact via this mechanism, management recommendations differ from other monoamine oxidase inhibitors. Refer to monographs specific to those agents for details. Risk X: Avoid combination

Multivitamins/Fluoride (with ADE): May decrease the serum concentration of Amphetamines. More specifically, the ascorbic acid (vitamin C) in many multivitamins may decrease amphetamine concentrations. Risk C: Monitor therapy

Multivitamins/Minerals (with ADEK, Folate, Iron): May decrease the serum concentration of Amphetamines. Risk C: Monitor therapy

Multivitamins/Minerals (with AE, No Iron): May decrease the serum concentration of Amphetamines. Specifically, vitamin C may impair absorption of amphetamines. 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

Opioid Agonists: Amphetamines may enhance the analgesic effect of Opioid Agonists. Risk C: Monitor therapy

Ozanimod: May enhance the hypertensive effect of Sympathomimetics. Risk C: Monitor therapy

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

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: 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

Pimozide: Agents With Seizure Threshold Lowering Potential may enhance the adverse/toxic effect of Pimozide. Specifically, the risk of seizures may be increased. Risk C: Monitor therapy

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

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

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

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

Quinolones: Amphetamines may enhance the cardiotoxic effect of Quinolones. 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

Selective Serotonin Reuptake Inhibitors (Strong CYP2D6 Inhibitors): Amphetamines may enhance the serotonergic effect of Selective Serotonin Reuptake Inhibitors (Strong CYP2D6 Inhibitors). This could result in serotonin syndrome. Selective Serotonin Reuptake Inhibitors (Strong CYP2D6 Inhibitors) may increase the serum concentration of Amphetamines. Management: Monitor for amphetamine toxicities, including serotonin syndrome/serotonin toxicity (eg, hyperreflexia, clonus, hyperthermia, diaphoresis, tremor, autonomic instability). Initiate amphetamines at lower doses, monitor frequently, and adjust dose as needed. Risk C: Monitor therapy

Serotonergic Agents (High Risk): Amphetamines may enhance the serotonergic effect of Serotonergic Agents (High Risk). This could result in serotonin syndrome. Management: Monitor for signs and symptoms of serotonin syndrome/serotonin toxicity (eg, hyperreflexia, clonus, hyperthermia, diaphoresis, tremor, autonomic instability). Initiate amphetamines at lower doses, monitor frequently, and adjust doses as needed. Risk C: Monitor therapy

Sertindole: Agents With Seizure Threshold Lowering Potential may enhance the adverse/toxic effect of Sertindole. Specifically, the risk of seizures may be increased. Risk C: Monitor therapy

Sibutramine: May enhance the adverse/toxic effect of Centrally Acting Weight Loss Agents. Risk X: Avoid combination

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

Solriamfetol: Sympathomimetics may enhance the hypertensive effect of Solriamfetol. Sympathomimetics may enhance the tachycardic effect of Solriamfetol. Risk C: Monitor therapy

Solriamfetol: CNS Stimulants may enhance the hypertensive effect of Solriamfetol. CNS Stimulants may enhance the tachycardic effect of Solriamfetol. Risk C: Monitor therapy

Sulpiride: Agents With Seizure Threshold Lowering Potential may enhance the adverse/toxic effect of Sulpiride. Specifically, the risk of seizures may be increased. Risk C: Monitor therapy

Sympathomimetics: May enhance the adverse/toxic effect of other Sympathomimetics. Risk C: Monitor therapy

Tedizolid: May enhance the hypertensive effect of Sympathomimetics. Tedizolid may enhance the tachycardic effect of Sympathomimetics. Risk C: Monitor therapy

Thioridazine: 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

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

Tricyclic Antidepressants: May enhance the adverse/toxic effect of Amphetamines. Tricyclic Antidepressants may potentiate the cardiovascular effects of Amphetamines. Amphetamines may enhance the serotonergic effect of Tricyclic Antidepressants. This could result in serotonin syndrome. Management: Monitor for signs and symptoms of serotonin syndrome/serotonin toxicity (eg, hyperreflexia, clonus, hyperthermia, diaphoresis, tremor, autonomic instability, mental status changes) and increased cardiovascular effects when these agents are combined. 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

Urinary Acidifying Agents: May decrease the serum concentration of Amphetamines. Risk C: Monitor therapy

Ziprasidone: Agents With Seizure Threshold Lowering Potential may enhance the adverse/toxic effect of Ziprasidone. Specifically, the risk of seizures may be increased. 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

Reproductive Considerations

Phentermine was evaluated in patients with infertility and overweight/obesity. Patients in the single center retrospective study (n=55) used contraception during therapy and were instructed to stop phentermine 1 month prior to trying to conceive. Although patients treated with phentermine had significant weight loss, pregnancy and live birth rates were not increased between patients who lost <5% or >5% of their initial body weight (Chang 2020).

Obesity increases the risk of infertility. Optimal weight control prior to conception improves pregnancy outcomes. However, medications for weight loss are not recommended prior to pregnancy due to safety issues and adverse events. Weight loss medications should be discontinued prior to conception (ACOG 2021; Wharton 2020).

Pregnancy Considerations

Information related to the use of phentermine during pregnancy is limited (D'Adesky 2019; Jones 2002; McElhatton 2006).

An increased risk of adverse maternal and fetal events is associated with obesity. However, moderate gestational weight gain based on pre-pregnancy BMI is required for positive fetal outcomes in all pregnancies, including patients with overweight or obesity. Therefore, medications for weight loss therapy are not recommended during pregnancy (ACOG 2021; Wharton 2020). Use of phentermine is contraindicated during pregnancy (lack of potential benefit and possible fetal harm).

Breastfeeding Considerations

It is not known if phentermine is present in breast milk; however, other amphetamines have been detected in breast milk.

Due to safety concerns, medications for weight loss therapy are not recommended for patients who are breastfeeding (Wharton 2020). Use of phentermine is contraindicated in breastfeeding patients.

Dietary Considerations

Capsules, tablets (excluding Lomaira): Should be taken before breakfast or 1 to 2 hours after breakfast.

Tablet (Lomaira only): Should be taken 30 minutes before meals.

Monitoring Parameters

Weight and waist circumference every month for the first 3 months, then at 3-month intervals (Apovian 2015); BP; CNS effects (eg, delirium, mania, psychosis); signs/symptoms of primary pulmonary hypertension (eg, new-onset dyspnea, chest pain, syncope, lower extremity edema).

Reference Range

Adult classification of weight by BMI (kg/m2):

Underweight: <18.5

Normal: 18.5 to 24.9

Overweight: 25 to 29.9

Obesity, class I: 30 to 34.9

Obesity, class II: 35 to 39.9

Obesity, class III: ≥40

Waist circumference: In adults with a BMI of 25 to 34.9 kg/m2, high-risk waist circumference is defined as:

Males >102 cm (>40 in).

Females >88 cm (>35 in).

Mechanism of Action

Phentermine is a sympathomimetic amine with pharmacologic properties similar to the amphetamines. The mechanism of action in reducing appetite appears to be secondary to CNS effects, including stimulation of the hypothalamus to release norepinephrine.

Pharmacokinetics (Adult Data Unless Noted)

Absorption: Well absorbed.

Distribution: Vd: 348 L.

Protein binding: 17.5%.

Metabolism: Hepatic via p-hydroxylation (aromatic ring) and N-oxidation (aliphatic side chain); primarily metabolized by CYP3A4 (but does not show extensive metabolism).

Half-life elimination: ~20 hours.

Time to peak: 3 to 4.4 hours.

Excretion: Primarily urine (62% to 85% as unchanged drug).

Pharmacokinetics: Additional Considerations (Adult Data Unless Noted)

Altered kidney function: Exposure increases can be expected in patients with renal impairment.

Brand Names: International
International Brand Names by Country
For country code abbreviations (show table)

  • (AU) Australia: Alenami | Duromine | Metermine | Phentermine gh | Phentermine juno er | Phentermine sandoz | Phentodur;
  • (BE) Belgium: Ionamin;
  • (CH) Switzerland: Adipex | Ionamine | Normaform;
  • (CL) Chile: Compulxine | Duromine | Fentex | Finapet | Obexol | Sentis;
  • (CZ) Czech Republic: Adipex | Mirapront;
  • (DO) Dominican Republic: Duromine | Obexol | Supress p | Terfamex;
  • (EC) Ecuador: Duromine | Novocetonil | Obexol | Sentis;
  • (FI) Finland: Mirapront;
  • (GB) United Kingdom: Duromine | Ionamin;
  • (HK) Hong Kong: Duromine | Panbesy | Phentermine | Redusa;
  • (HU) Hungary: Adipex;
  • (ID) Indonesia: Mirapront;
  • (IE) Ireland: Ionamin;
  • (IL) Israel: Novirasin | Razin;
  • (KR) Korea, Republic of: Adipex | Artmin | Bm zine | Bmzine | Daehwa nobse | Dietamin | Festin | Furimin | Hanbul phentermin | Hutermin | Hutermine semi | Lediphen | Metamax | Panbesi | Panbesy | Pender | Penimin | Penmin | Pentazen | Pentmin | Phedin | Phenkini | Phentazen | Phentazia | Phentemy | Phentermine | Ptm | Retis | Sinsphen | Slemin | Tintin | Weltmine;
  • (LT) Lithuania: Adipex | Mirapront;
  • (LU) Luxembourg: Ionamine;
  • (LV) Latvia: Adipex | Mirapront;
  • (MX) Mexico: Acxion | Acxion ap | Acxion c | Definitum | Disebsin | Fentermina | Ifa acxion | Ifa-reduccing s | Ina10 | Novagrit | Raamcaps | Reducap | Sinpet | Terfamex | Terfamex od;
  • (MY) Malaysia: Adipex | Axcel phentermine | Duromine | Ionamin | Panbesy;
  • (NO) Norway: Adipex-p;
  • (NZ) New Zealand: Duromine | Metermine | Umine;
  • (PE) Peru: Obexol;
  • (PH) Philippines: Duromine | Ionamin | Phentermine;
  • (PL) Poland: Mirapront;
  • (PR) Puerto Rico: Adipex-p | Fastin | Ionamin | Lomaira | Phentermine HCL;
  • (PY) Paraguay: Obexol | Sentis | Terfamex;
  • (SG) Singapore: Duromine | Ionamin | Panbesy | Umine;
  • (SK) Slovakia: Adipex;
  • (TH) Thailand: Duromine | Ionamin | Mirapront | Panbesy | Phentermine;
  • (VE) Venezuela, Bolivarian Republic of: Mirubal;
  • (ZA) South Africa: Duromine | Minex | Minobese | Musalos | Panbesy
  1. Adipex-P (phentermine) [prescribing information]. Parsippany, NJ: Teva Pharmaceuticals USA Inc; September 2020.
  2. Alexander J, Cheng YH, Choudhary J, Dinesh A. Phentermine (Duromine) precipitated psychosis. Aust N Z J Psychiatry. 2011;45(8):684-685. doi:10.3109/00048674.2011.580721 [PubMed 21595510]
  3. Alsuhibani A, Alrasheed M, Gari M, Hincapie AL, Guo JJ. Descriptive analysis of reported adverse events associated with anti-obesity medications using FDA Adverse Event Reporting System (FAERS) databases 2013-2020. Int J Clin Pharm. 2022;44(1):172-179. doi:10.1007/s11096-021-01330-2 [PubMed 34564826]
  4. American College of Obstetricians and Gynecologists (ACOG) Committee on Practice Bulletins–Obstetrics. ACOG Practice Bulletin No. 230: Obesity in pregnancy. Obstet Gynecol. 2021;137(6):e128-e144. doi:10.1097/AOG.0000000000004395 [PubMed 34011890]
  5. Apovian CM, Aronne LJ, Bessesen DH, et al; Endocrine Society. Pharmacological management of obesity: an endocrine Society clinical practice guideline. J Clin Endocrinol Metab. 2015;100(2):342-362. doi:10.1210/jc.2014-3415 [PubMed 25590212]
  6. Bagri S, Reddy G. Delirium with manic symptoms induced by diet pills. J Clin Psychiatry. 1998;59(2):83. doi:10.4088/jcp.v59n0207d [PubMed 9501893]
  7. Bang WD, Kim JY, Yu HT, et al. Pulmonary hypertension associated with use of phentermine. Yonsei Med J. 2010;51(6):971-973. doi:10.3349/ymj.2010.51.6 [PubMed 20879069]
  8. Brauer LH, Johanson CE, Schuster CR, Rothman RB, de Wit H. Evaluation of phentermine and fenfluramine, alone and in combination, in normal, healthy volunteers. Neuropsychopharmacology. 1996;14(4):233-241. doi:10.1016/0893-133X(95)00113-R [PubMed 8924191]
  9. Chang JJ, Lathi RB, Kim SH. A retrospective study examining phentermine on preconception weight loss and pregnancy outcomes. Endocr Pract. 2020;26(9):990-996. doi:10.4158/EP-2019-0609 [PubMed 33471704]
  10. Cleare AJ. Phentermine, psychosis, and family history. J Clin Psychopharmacol. 1996;16(6):470-471. doi:10.1097/00004714-199612000-00020 [PubMed 8959483]
  11. Connolly HM, Crary JL, McGoon MD, et al. Valvular heart disease associated with fenfluramine-phentermine. N Engl J Med. 1997;337(9):581-588. doi:10.1056/NEJM199708283370901. Erratum in: N Engl J Med. 1997;337(24):1783. [PubMed 9271479]
  12. D'Adesky N, Ghosh S. Phentermine use during first and second trimesters associated with fetal stroke. Cureus. 2019;11(11):e6170. doi:10.7759/cureus.6170 [PubMed 31890378]
  13. Eddahibi S, Adnot S. Anorexigen-induced pulmonary hypertension and the serotonin (5-HT) hypothesis: lessons for the future in pathogenesis. Respir Res. 2002;3(1):9. doi:10.1186/rr181 [PubMed 11806844]
  14. Franke KB, Psaltis PJ. Coronary vasospasm induced by phentermine. Mayo Clin Proc. 2019;94(7):1138-1140. doi:10.1016/j.mayocp.2019.05.021 [PubMed 31272562]
  15. Gardin JM, Schumacher D, Constantine G, Davis KD, Leung C, Reid CL. Valvular abnormalities and cardiovascular status following exposure to dexfenfluramine or phentermine/fenfluramine. JAMA. 2000;283(13):1703-1709. doi:10.1001/jama.283.13.1703 [PubMed 10755496]
  16. Garvey WT, Mechanick JI, Brett EM, et al; reviewers of the AACE/ACE obesity clinical practice guidelines. American Association of Clinical Endocrinologists and American College of Endocrinology comprehensive clinical practice guidelines for medical care of patients with obesity. Endocr Pract. 2016;22(suppl 3):1-203. doi:10.4158/EP161365.GL [PubMed 27219496]
  17. Gorelik E, Gorelik B, Masarwa R, Perlman A, Hirsh-Raccah B, Matok I. The cardiovascular safety of antiobesity drugs-analysis of signals in the FDA Adverse Event Report System Database. Int J Obes (Lond). 2020;44(5):1021-1027. doi:10.1038/s41366-020-0544-4 [PubMed 32152496]
  18. Grunvald E, Shah R, Hernaez R, et al. AGA clinical practice guideline on pharmacological interventions for adults with obesity. Gastroenterology. 2022;163(5):1198-1225. doi:10.1053/j.gastro.2022.08.045 [PubMed 36273831]
  19. Homola J, Hieber R. Combination of venlafaxine and phentermine/topiramate induced psychosis: a case report. Ment Health Clin. 2018;8(2):95-99. doi:10.9740/mhc.2018.03.095 [PubMed 29955552]
  20. Hung YM, Chang JC. Weight-reducing regimen associated with polymorphic ventricular tachycardia. Am J Emerg Med. 2006;24(6):714-716. doi:10.1016/j.ajem.2006.02.004 [PubMed 16984841]
  21. Jo HS, Wang SM, Kim JJ. Recurrent psychosis after phentermine administration in a young female: a case report. Clin Psychopharmacol Neurosci. 2019;17(1):130-133. doi:10.9758/cpn.2019.17.1.130 [PubMed 30690949]
  22. Jones KL, Johnson KA, Dick LM, Felix RJ, Kao KK, Chambers CD. Pregnancy outcomes after first trimester exposure to phentermine/fenfluramine. Teratology. 2002;65(3):125-130. doi:10.1002/tera.10023 [PubMed 11877776]
  23. Kang JG, Park CY. Anti-obesity drugs: a review about their effects and safety. Diabetes Metab J. 2012;36(1):13-25. doi:10.4093/dmj.2012.36.1.13 [PubMed 22363917]
  24. Kumar S, Mogalapalli A, Srinivasamurthy R, Hussain ST, Mar PL. Supraventricular tachycardia with the use of phentermine: case report and review of literature. Postgrad Med. 2021;133(4):454-457. doi:10.1080/00325481.2021.1901476 [PubMed 33686912]
  25. Lewis KH, Fischer H, Ard J, et al. Safety and effectiveness of longer-term phentermine use: clinical outcomes from an electronic health record cohort. Obesity (Silver Spring). 2019;27(4):591-602. doi:10.1002/oby.22430 [PubMed 30900410]
  26. Lomaira (phentermine) [prescribing information]. Newtown, PA: KVK-Tech; December 2023.
  27. McElhatton P, Stephens S. Preliminary data on pregnancy outcome following exposure to drugs for the treatment of obesity In pregnancy. 34th Annual Conference of the European Teratology Society, 3rd–6th September 2006, Abano Terme, Padova, Italy. Reprod Toxicol. 2006;22(2):277-278.
  28. McNeill S, Almallouhi E, Lowe FJ, Turan TN. Phentermine associated recurrent intracerebral hemorrhage. J Neurol Sci. 2018;393:135-137. doi:10.1016/j.jns.2018.08.017 [PubMed 30179740]
  29. Page RL 2nd, O'Bryant CL, Cheng D, et al; American Heart Association Clinical Pharmacology and Heart Failure and Transplantation Committees of the Council on Clinical Cardiology; Council on Cardiovascular Surgery and Anesthesia; Council on Cardiovascular and Stroke Nursing; and Council on Quality of Care and Outcomes Research. Drugs that may cause or exacerbate heart failure: a scientific statement from the American Heart Association. Circulation. 2016;134(6):e32-e69. doi:10.1161/CIR.0000000000000426 [PubMed 27400984]
  30. Perreault L, Reid TJ. Obesity in adults: drug therapy. Post TW, ed. UpToDate. Waltham, MA: UpToDate Inc. http://www.uptodate.com. Accessed April 9, 2024.
  31. Phentermine hydrochloride capsules [prescribing information]. Sellersville, PA: Teva Pharmaceuticals; January 2013.
  32. Prasad M, El Sabbagh A, Rihal C, Lerman A. Phentermine and coronary vasospasm-induced myocardial infarction. Mayo Clin Proc. 2019;94(7):1374-1377. doi:10.1016/j.mayocp.2018.08.029 [PubMed 31272579]
  33. Qsymia (phentermine and topiramate) [prescribing information]. Winchester, KY: Vivus Inc; April 2013.
  34. Raison CL, Klein HM. Psychotic mania associated with fenfluramine and phentermine use. Am J Psychiatry. 1997;154(5):711. doi:10.1176/ajp.154.5.711a [PubMed 9137134]
  35. Refer to manufacturer's labeling.
  36. Shao EX, Wilson GJ, Ranganathan D. Phentermine induced acute interstitial nephritis. BMJ Case Rep. 2017;2017:bcr2017219452. doi:10.1136/bcr-2017-219452 [PubMed 28280086]
  37. Siebenhofer A, Jeitler K, Horvath K, et al. Long-term effects of weight-reducing drugs in people with hypertension. Cochrane Database Syst Rev. 2016;3:CD007654. doi:10.1002/14651858.CD007654.pub4 [PubMed 26934640]
  38. Slørdal L, Spigset O. Heart failure induced by non-cardiac drugs. Drug Saf. 2006;29(7):567-586. doi:10.2165/00002018-200629070-00003 [PubMed 16808550]
  39. Tobbia P, Norris LA, Klima LD. Ventricular fibrillation coinciding with phentermine initiation. BMJ Case Rep. 2012;2012:bcr2012006410. doi:10.1136/bcr-2012-006410 [PubMed 23076689]
  40. Tomita T, Zhao Q. Autopsy findings of heart and lungs in a patient with primary pulmonary hypertension associated with use of fenfluramine and phentermine. Chest. 2002;121(2):649-652. doi:10.1378/chest.121.2.649 [PubMed 11834685]
  41. Wharton S, Lau DCW, Vallis M, et al. Obesity in adults: a clinical practice guideline. CMAJ. 2020;192(31):E875-E891. doi:10.1503/cmaj.191707 [PubMed 32753461]
  42. Yanovski SZ, Yanovski JA. Long-term drug treatment for obesity: a systematic and clinical review. JAMA. 2014;311(1):74-86. doi:10.1001/jama.2013.281361 [PubMed 24231879]
  43. Zimmer JE, Gregory RJ. Bipolar depression associated with fenfluramine and phentermine. J Clin Psychiatry. 1998;59(7):383-384. doi:10.4088/jcp.v59n0707e [PubMed 9714271]
Topic 9765 Version 479.0

آیا می خواهید مدیلیب را به صفحه اصلی خود اضافه کنید؟