Methazolamide

Marked renal impairment: Contraindicated.

Marked hepatic impairment: Contraindicated.

Adrenal gland failure, hyponatraemia, hypokalaemia, hyperchloraemic acidosis, liver cirrhosis, and long-term use in angle-closure glaucoma. Marked renal or hepatic impairment.

Patient with pulmonary obstruction or emphysema, prediabetes, or diabetes mellitus. Pregnancy and lactation. Concomitant administration of high-dose aspirin.

Significant: Precipitation or aggravation of respiratory acidosis and/or acute respiratory failure, precipitation of hepatic encephalopathy (in patients with cirrhosis) or hepatic coma (in patients with cirrhosis or hepatic insufficiency); increased potassium excretion, change in glucose control, impaired mental alertness and/or physical coordination.
Ear and labyrinth disorders: Auditory disturbance, tinnitus.
Eye disorders: Transient myopia.
Gastrointestinal disorders: Dysgeusia, nausea, vomiting, diarrhoea, melaena.
General disorders and administration site conditions: Fatigue, malaise.
Hepatobiliary disorders: Hepatic insufficiency.
Metabolism and nutrition disorders: Loss of appetite, metabolic acidosis, electrolyte imbalance.
Nervous system disorders: Paraesthesia, drowsiness, confusion, convulsions, flaccid paralysis.
Renal and urinary disorders: Polyuria, haematuria, glycosuria, crystalluria, nephrolithiasis.
Skin and subcutaneous tissue disorders: Urticaria, photosensitivity.
Potentially Fatal: Rarely, Stevens-Johnson syndrome, toxic epidermal necrolysis, fulminant hepatic necrosis, agranulocytosis, aplastic anaemia, and other blood dyscrasias.

Monitor CBC, platelet count (baseline and periodically), and serum electrolytes (periodically).

Symptoms: CNS effects, electrolyte imbalance, and development of an acidotic state.

Management: Symptomatic and supportive treatment. Monitor and correct electrolyte levels (particularly potassium) and blood pH levels.

Concomitant use with steroids may result in hypokalaemia.
Potentially Fatal: Concomitant administration of high-dose aspirin may cause anorexia, tachypnoea, lethargy, and coma.

May cause false-negative aldosterone/renin ratio (ARR).

Description:
Overview: Methazolamide is a carbonic anhydrase inhibitor.
Mechanism of Action: Methazolamide inhibits carbonic anhydrase, leading to decreased secretion of aqueous humour and a consequent reduction in intraocular pressure.
Onset: 2-4 hours.
Duration: 10-18 hours.
Pharmacokinetics:
Absorption: Slowly and well absorbed from the gastrointestinal. Time to peak plasma concentration: 1-2 hours.
Distribution: Extensively distributed throughout the body, including the plasma, CSF, aqueous humour of the eye, RBC, bile, and extracellular fluid. Volume of distribution: 17-23 L. Plasma protein binding: Approx 55%.
Metabolism: Partially metabolised in the liver.
Excretion: Via urine (approx 15-30%). Elimination half-life: Approx 14 hours.

Source: National Center for Biotechnology Information. PubChem Compound Summary for CID 4100, Methazolamide. https://pubchem.ncbi.nlm.nih.gov/compound/Methazolamide. Accessed Oct. 28, 2025.

Store between 20-25°C.

Antiglaucoma Preparations

S01EC05 - methazolamide ; Belongs to the class of carbonic anhydrase inhibitors. Used in the treatment of glaucoma.

Brayfield A, Cadart C (eds). Methazolamide. Martindale: The Complete Drug Reference [online]. London. Pharmaceutical Press. https://www.medicinescomplete.com. Accessed 13/10/2025.

Methazolamide Tablet (ANI Pharmaceuticals, Inc.). DailyMed. Source: U.S. National Library of Medicine. https://dailymed.nlm.nih.gov/dailymed. Accessed 13/10/2025.

Methazolamide. Gold Standard Drug Database in ClinicalKey [online]. Elsevier Inc. https://www.clinicalkey.com. Accessed 13/10/2025.

Methazolamide. UpToDate Lexidrug, AHFS DI (Adult and Pediatric) Online. American Society of Health-System Pharmacists, Inc. Waltham, MA. UpToDate, Inc. https://online.lexi.com. Accessed 13/10/2025.

Methazolamide. UpToDate Lexidrug, Lexi-Drugs Multinational Online. Waltham, MA. UpToDate, Inc. https://online.lexi.com. Accessed 13/10/2025.