Methazolamide
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Gerald Chi
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Overview
Methazolamide is a carbonic anhydrase inhibitor that is FDA approved for the {{{indicationType}}} of ocular conditions where lowering intraocular pressure is likely to be of therapeutic benefit, such as chronic open-angle glaucoma, secondary glaucoma, and preoperatively in acute angle-closure glaucoma where lowering the intraocular pressure is desired before surgery. Common adverse reactions include diarrhea, taste alterations, loss of appetite, nausea, vomiting, confusion, paresthesia, somnolence, polyuria, fatigue, and malaise.
Adult Indications and Dosage
FDA-Labeled Indications and Dosage (Adult)
Glaucoma
- Dosing Information
- 50–100 mg two or three times daily
Off-Label Use and Dosage (Adult)
Guideline-Supported Use
There is limited information regarding Off-Label Guideline-Supported Use of Methazolamide in adult patients.
Non–Guideline-Supported Use
There is limited information regarding Off-Label Non–Guideline-Supported Use of Methazolamide in adult patients.
Pediatric Indications and Dosage
FDA-Labeled Indications and Dosage (Pediatric)
- The safety and effectiveness of methazolamide in children have not been established.
Off-Label Use and Dosage (Pediatric)
Guideline-Supported Use
There is limited information regarding Off-Label Guideline-Supported Use of Methazolamide in pediatric patients.
Non–Guideline-Supported Use
There is limited information regarding Off-Label Non–Guideline-Supported Use of Methazolamide in pediatric patients.
Contraindications
- Methazolamide therapy is contraindicated in situations in which sodium and/or potassium serum levels are depressed, in cases of marked kidney or liver disease or dysfunction, in adrenal gland failure, and in hyperchloremic acidosis.
- In patients with cirrhosis, use may precipitate the development of hepatic encephalopathy.
- Long-term administration of methazolamide is contraindicated in patients with angle-closure glaucoma, since organic closure of the angle may occur in spite of lowered intraocular pressure.
Warnings
- Fatalities have occurred, although rarely, due to severe reactions to sulfonamides including Stevens-Johnson syndrome, toxic epidermal necrolysis, fulminant hepatic necrosis, agranulocytosis, aplastic anemia, and other blood dyscrasias. Hypersensitivity reactions may recur when a sulfonamide is readministered, irrespective of the route of administration.
- If hypersensitivity or other serious reactions occur, the use of this drug should be discontinued.
- Caution is advised for patients receiving high-dose aspirin and methazolamide concomitantly, as anorexia, tachypnea, lethargy, coma, and death have been reported with concomitant use of high-dose aspirin and carbonic anhydrase inhibitors.
Precautions
- Potassium excretion is increased initially upon administration of methazolamide and in patients with cirrhosis or hepatic insufficiency could precipitate a hepatic coma.
- In patients with pulmonary obstruction or emphysema, where alveolar ventilation may be impaired, methazolamide should be used with caution because it may precipitate or aggravate acidosis.
Laboratory Tests
- To monitor for hematologic reactions common to all sulfonamides, it is recommended that a baseline CBC and platelet count be obtained on patients prior to initiating methazolamide therapy and at regular intervals during therapy. If significant changes occur, early discontinuance and institution of appropriate therapy are important. Periodic monitoring of serum electrolytes is also recommended.
Adverse Reactions
Clinical Trials Experience
There is limited information regarding Clinical Trial Experience of Methazolamide in the drug label.
Postmarketing Experience
- Adverse reactions, occurring most often early in therapy, include paresthesias, particularly a “tingling” feeling in the extremities; hearing dysfunction or tinnitus; fatigue; malaise; loss of appetite; taste alteration; gastrointestinal disturbances such as nausea, vomiting, and diarrhea; polyuria; and occasional instances of drowsiness and confusion.
- Metabolic acidosis and electrolyte imbalance may occur.
- Transient myopia has been reported. This condition invariably subsides upon diminution or discontinuance of the medication.
- Other occasional adverse reactions include urticaria, melena, hematuria, glycosuria, hepatic insufficiency, flaccid paralysis, photosensitivity, convulsions, and, rarely, crystalluria and renal calculi.
- Fatalities have occurred, although rarely, due to severe reactions to sulfonamides including Stevens-Johnson syndrome, toxic epidermal necrolysis, fulminant hepatic necrosis, agranulocytosis, aplastic anemia, and other blood dyscrasias.
Drug Interactions
- Methazolamide should be used with caution in patients on steroid therapy because of the potential for developing hypokalemia.
- Caution is advised for patients receiving high-dose aspirin and methazolamide concomitantly, as anorexia, tachypnea, lethargy, coma and death have been reported with concomitant use of high-dose aspirin and carbonic anhydrase inhibitors.
Use in Specific Populations
Pregnancy
- Pregnancy Category C
- Methazolamide has been shown to be teratogenic (skeletal anomalies) in rats when given in doses approximately 40 times the human dose. There are no adequate and well controlled studies in pregnant women. Methazolamide should be used during pregnancy only if the potential benefit justifies the potential risk to the fetus.
- Australian Drug Evaluation Committee (ADEC) Pregnancy Category
There is no Australian Drug Evaluation Committee (ADEC) guidance on usage of Methazolamide in women who are pregnant.
Labor and Delivery
There is no FDA guidance on use of Methazolamide during labor and delivery.
Nursing Mothers
- It is not known whether this drug is excreted in human milk. Because many drugs are excreted in human milk and because of the potential for serious adverse reactions in nursing infants from methazolamide, a decision should be made whether to discontinue nursing or to discontinue the drug, taking into account the importance of the drug to the mother.
Pediatric Use
- The safety and effectiveness of methazolamide in children have not been established.
Geriatic Use
There is no FDA guidance on the use of Methazolamide with respect to geriatric patients.
Gender
There is no FDA guidance on the use of Methazolamide with respect to specific gender populations.
Race
There is no FDA guidance on the use of Methazolamide with respect to specific racial populations.
Renal Impairment
There is no FDA guidance on the use of Methazolamide in patients with renal impairment.
Hepatic Impairment
There is no FDA guidance on the use of Methazolamide in patients with hepatic impairment.
Females of Reproductive Potential and Males
There is no FDA guidance on the use of Methazolamide in women of reproductive potentials and males.
Immunocompromised Patients
There is no FDA guidance one the use of Methazolamide in patients who are immunocompromised.
Administration and Monitoring
Administration
- Oral
Monitoring
- It is recommended that a baseline CBC and platelet count be obtained on patients prior to initiating methazolamide therapy and at regular intervals during therapy. If significant changes occur, early discontinuance and institution of appropriate therapy are important. Periodic monitoring of serum electrolytes is also recommended.
IV Compatibility
There is limited information regarding IV Compatibility of Methazolamide in the drug label.
Overdosage
Acute Overdose
Signs and Symptoms
- No data are available regarding methazolamide overdosage in humans as no cases of acute poisoning with this drug have been reported. Animal data suggest that even a high dose of methazolamide is nontoxic.
- Electrolyte imbalance, development of an acidotic state, and central nervous system effects might be expected to occur. Serum electrolyte levels (particularly potassium) and blood pH levels should be monitored.
Management
- No specific antidote is known. Treatment should be symptomatic and supportive.
Chronic Overdose
There is limited information regarding Chronic Overdose of Methazolamide in the drug label.
Pharmacology
Methazolamide
| |
Systematic (IUPAC) name | |
N-(3-methyl-5-sulfamoyl-3H- 1,3,4-thiadiazol-2-ylidene) ethanamide | |
Identifiers | |
CAS number | |
ATC code | S01 |
PubChem | |
DrugBank | |
Chemical data | |
Formula | Template:OrganicBox atomTemplate:OrganicBox atomTemplate:OrganicBoxTemplate:OrganicBoxTemplate:OrganicBoxTemplate:OrganicBoxTemplate:OrganicBoxTemplate:OrganicBoxTemplate:OrganicBoxTemplate:OrganicBoxTemplate:OrganicBoxTemplate:OrganicBoxTemplate:OrganicBoxTemplate:OrganicBox atomTemplate:OrganicBoxTemplate:OrganicBox atomTemplate:OrganicBoxTemplate:OrganicBoxTemplate:OrganicBox atomTemplate:OrganicBoxTemplate:OrganicBoxTemplate:OrganicBoxTemplate:OrganicBox |
Mol. mass | 236.274 g/mol |
Pharmacokinetic data | |
Bioavailability | ? |
Protein binding | 55% |
Metabolism | ? |
Half life | 14 hours |
Excretion | ? |
Therapeutic considerations | |
Pregnancy cat. |
C(US) |
Legal status |
[[Prescription drug|Template:Unicode-only]](US) |
Routes | Oral |
Mechanism of Action
Structure
Pharmacodynamics
There is limited information regarding Pharmacodynamics of Methazolamide in the drug label.
Pharmacokinetics
There is limited information regarding Pharmacokinetics of Methazolamide in the drug label.
Nonclinical Toxicology
- Carcinogenesis, Mutagenesis, Impairment of Fertility
- Long-term studies in animals to evaluate the carcinogenic potential of methazolamide and its effect on fertility have not been conducted. Methazolamide was not mutagenic in the Ames bacterial test.
Clinical Studies
There is limited information regarding Clinical Studies of Methazolamide in the drug label.
How Supplied
- Methazolamide Tablets USP, 25 mg, are round, white tablets, debossed “EFF” on one side and “21” on the other side and are supplied in bottles of 100, NDC 55806-021-03.
- Methazolamide Tablets USP, 50 mg, are round, white, scored tablets debossed “EFF” on one side and “20” on the other side and are supplied in bottles of 100, NDC 55806-020-03.
- Store at 20° to 25°C (68° to 77°F).
- Dispense in a tight container as defined in the USP, with a child-resistant closure (as required).
Storage
There is limited information regarding Methazolamide Storage in the drug label.
Images
Drug Images
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Package and Label Display Panel
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Patient Counseling Information
There is limited information regarding Patient Counseling Information of Methazolamide in the drug label.
Precautions with Alcohol
- Alcohol-Methazolamide interaction has not been established. Talk to your doctor about the effects of taking alcohol with this medication.
Brand Names
- Neptazane®
- Glauctabs®[1]
Look-Alike Drug Names
- A® — B®[2]
Drug Shortage Status
Price
References
The contents of this FDA label are provided by the National Library of Medicine.
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