Version July 2025
Glaucoma: Oral: 50 to 100 mg 2 to 3 times daily.
Contraindicated in marked renal dysfunction.
Contraindicated in marked hepatic dysfunction.
Refer to adult dosing.
The following adverse drug reactions are derived from product labeling unless otherwise specified.
Frequency not defined:
Dermatologic: Skin photosensitivity, urticaria
Endocrine & metabolic: Electrolyte disorder, metabolic acidosis
Gastrointestinal: Anorexia, diarrhea, dysgeusia, melena, nausea, vomiting
Genitourinary: Crystalluria, glycosuria, hematuria, polyuria
Hepatic: Hepatic impairment
Nervous system: Confusion, drowsiness, fatigue, flaccid paralysis, malaise, paresthesia, seizure
Otic: Auditory disturbance, tinnitus
Renal: Nephrolithiasis
Postmarketing:
Dermatologic: Stevens-Johnson syndrome (Trubiano 2019), toxic epidermal necrolysis (Sohn 2021)
Hematologic & oncologic: Agranulocytosis (Werblin 1979), aplastic anemia (Werblin 1979), leukopenia (Cohen 1989), pure red cell aplasia (Krivoy 1981), thrombocytopenia (Cohen 1989)
Hepatic: Hepatitis (Krivoy 1981)
Ophthalmic: Acute angle-closure glaucoma (Aref 2013), myopia (Aref 2013)
Marked kidney or liver dysfunction; adrenal gland failure; cirrhosis; hyperchloremic acidosis; hyponatremia; hypokalemia; long-term treatment of angle-closure glaucoma
Concerns related to adverse effects:
• CNS effects: May impair mental alertness and/or physical coordination.
• Electrolyte disturbance: Initially, potassium excretion may be increased; periodically monitor serum electrolytes and signs of hypokalemia in at risk patients.
• Sulfonamide (“sulfa”) allergy: The FDA-approved product labeling for many medications containing a sulfonamide chemical group includes a broad contraindication in patients with a prior allergic reaction to sulfonamides. There is a potential for cross-reactivity between members of a specific class (eg, two antibiotic sulfonamides). However, concerns for cross-reactivity have previously extended to all compounds containing the sulfonamide structure (SO2NH2). An expanded understanding of allergic mechanisms indicates cross-reactivity between antibiotic sulfonamides and nonantibiotic sulfonamides may not occur or at the very least this potential is extremely low (Brackett 2004; Johnson 2005; Slatore 2004; Tornero 2004). In particular, mechanisms of cross-reaction due to antibody production (anaphylaxis) are unlikely to occur with nonantibiotic sulfonamides. T-cell-mediated (type IV) reactions (eg, maculopapular rash) are less well understood and it is not possible to completely exclude this potential based on current insights. In cases where prior reactions were severe (Stevens-Johnson syndrome/TEN), some clinicians choose to avoid exposure to these classes.
Disease-related concerns:
• Diabetes: Use with caution in patients with prediabetes or diabetes mellitus; may see a change in glucose control.
• Hepatic impairment: Use with caution in patients with hepatic impairment; may precipitate hepatic encephalopathy. Use is contraindicated in patients with marked liver impairment or cirrhosis.
• Respiratory disease: Use with caution in patients with respiratory disease such as emphysema or pulmonary obstruction; may precipitate or aggravate respiratory acidosis.
Excipient information presented when available (limited, particularly for generics); consult specific product labeling.
Tablet, Oral:
Generic: 25 mg, 50 mg
Yes
Tablets (methazolAMIDE Oral)
25 mg (per each): $1.84 - $5.11
50 mg (per each): $3.59 - $10.22
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.
Excipient information presented when available (limited, particularly for generics); consult specific product labeling.
Tablet, Oral:
Generic: 50 mg
Oral: May administer without regard to food.
Glaucoma: Treatment of chronic open-angle or secondary glaucoma; short-term therapy of acute angle-closure glaucoma prior to surgery
MethazolAMIDE may be confused with methenamine, methIMAzole, metOLazone
Neptazane may be confused with Nesacaine
None known.
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.
Amantadine: Carbonic Anhydrase Inhibitors may increase serum concentration of Amantadine. Risk C: Monitor
Amphetamines: Carbonic Anhydrase Inhibitors may decrease excretion of Amphetamines. Risk C: Monitor
Carbonic Anhydrase Inhibitors: May increase adverse/toxic effects of Carbonic Anhydrase Inhibitors. The development of acid-base disorders with concurrent use of ophthalmic and oral carbonic anhydrase inhibitors has been reported. Management: Avoid concurrent use of different carbonic anhydrase inhibitors if possible. Monitor patients closely for the occurrence of kidney stones and with regards to severity of metabolic acidosis. Risk X: Avoid
Desmopressin: Hyponatremia-Associated Agents may increase hyponatremic effects of Desmopressin. Risk C: Monitor
Diacerein: May increase therapeutic effects of Diuretics. Specifically, the risk for dehydration or hypokalemia may be increased. Risk C: Monitor
EPINEPHrine (Systemic): Diuretics may increase arrhythmogenic effects of EPINEPHrine (Systemic). Diuretics may decrease vasopressor effects of EPINEPHrine (Systemic). Risk C: Monitor
Flecainide: Carbonic Anhydrase Inhibitors may decrease excretion of Flecainide. Risk C: Monitor
Isocarboxazid: May increase hypotensive effects of Diuretics. Risk X: Avoid
Lithium: Carbonic Anhydrase Inhibitors may decrease serum concentration of Lithium. Risk C: Monitor
Memantine: Carbonic Anhydrase Inhibitors may increase serum concentration of Memantine. Risk C: Monitor
MetFORMIN: Carbonic Anhydrase Inhibitors may increase adverse/toxic effects of MetFORMIN. Specifically, the risk of developing lactic acidosis may be increased. Risk C: Monitor
Methenamine: Carbonic Anhydrase Inhibitors may decrease therapeutic effects of Methenamine. Management: Consider avoiding the concomitant use of medications that alkalinize the urine, such as carbonic anhydrase inhibitors, and methenamine. Monitor for decreased therapeutic effects of methenamine if used concomitant with a carbonic anhydrase inhibitor. Risk D: Consider Therapy Modification
Opioid Agonists: May increase adverse/toxic effects of Diuretics. Opioid Agonists may decrease therapeutic effects of Diuretics. Risk C: Monitor
Piperacillin: May increase hypokalemic effects of Diuretics. Risk C: Monitor
Polyethylene Glycol-Electrolyte Solution: Diuretics may increase nephrotoxic effects of Polyethylene Glycol-Electrolyte Solution. Risk C: Monitor
Salicylates: May increase adverse/toxic effects of Carbonic Anhydrase Inhibitors. Salicylate toxicity might be enhanced by this same combination. Management: Avoid these combinations when possible.Dichlorphenamide use with high-dose aspirin as contraindicated. If another combination is used, monitor patients closely for adverse effects. Tachypnea, anorexia, lethargy, and coma have been reported. Risk D: Consider Therapy Modification
Sodium Phosphates: Diuretics may increase nephrotoxic effects of Sodium Phosphates. Specifically, the risk of acute phosphate nephropathy may be enhanced. Risk C: Monitor
Adverse events were observed in animal reproduction studies.
It is not known if methazolamide is excreted in breast milk. Due to the potential for serious adverse reactions in the nursing infant, a decision should be made whether to discontinue nursing or to discontinue the drug, taking into account the importance of treatment to the mother.
CBC and platelet count (baseline and periodically), serum electrolytes (periodically)
Noncompetitive inhibition of the enzyme carbonic anhydrase; thought that carbonic anhydrase is located at the luminal border of cells of the proximal tubule. When the enzyme is inhibited, there is an increase in urine volume and a change to an alkaline pH with a subsequent decrease in the excretion of titratable acid and ammonia.
Onset of action: Slow in comparison with acetazolamide (2 to 4 hours).
Peak effect: 6 to 8 hours.
Duration: 10 to 18 hours.
Absorption: Slow.
Distribution: Vd: 17 to 23 L.
Protein binding: ~55%.
Metabolism: Slowly from GI tract.
Half-life elimination: ~14 hours.
Excretion: Urine (~25% as unchanged drug).
