Classifications: eye preparation; carbonic anhydrase inhibitor; sulfonamide derivative; antiglaucoma;
Therapeutic: antiglaucoma; carbonic anhydrase inhibitor

Prototype: Acetazolamide
Pregnancy Category: C


25 mg, 50 mg tablets


Inhibits carbonic anhydrase activity in eye by reducing rate of aqueous humor formation with consequent lowering of intraocular pressure.

Therapeutic Effect

Effective in lowering intraocular pressure in glaucoma patients.


Adjunctive treatment in chronic simple (open-angle) glaucoma and secondary glaucoma and preoperatively in acute angle-closure glaucoma when delay of surgery is desired in order to lower intraocular pressure. May be used concomitantly with miotic and osmotic agents.


Glaucoma due to severe peripheral anterior synechiae, severe or absolute glaucoma, hemorrhagic glaucoma; hypokalemia, hyponatremia; dialysis; hepatic disease; renal disease, anuria, renal failure; pregnancy (category C).

Cautious Use

Pulmonary disease, COPD; diabetes mellitus; renal impairment; lactation.

Route & Dosage

Adult: PO 50–100 mg b.i.d. or t.i.d.


  • Give with meals to minimize GI distress.

Adverse Effects (≥1%)

Body as a Whole: Malaise, drowsiness, fatigue, lethargy. GI: Mild GI disturbance, anorexia. CNS: Headache, vertigo, paresthesias, mental confusion, depression.


Drug: Renal excretion of amphetamines, ephedrine, flecainide, quinidine, procainamide, tricyclic antidepressants may be decreased, thereby enhancing or prolonging their effects; increases renal excretion of lithium; excretion of phenobarbital may be increased; amphotericin B, corticosteroids may add to potassium loss; hypokalemia caused by methazolamide may predispose patients on digitalis glycosides to digitalis toxicity; patients on high doses of salicylates are at higher risk for salicylate toxicity.


Absorption: Slowly from GI tract. Onset: 2–4 h. Peak: 6–8 h. Duration: 10–18 h. Distribution: throughout body, concentrating in RBCs, plasma, and kidneys; crosses placenta. Metabolism: Partially in liver. Elimination: Primarily in urine.

Nursing Implications

Assessment & Drug Effects

  • Supervise ambulation in older adult, since drug may cause vertigo.
  • Assess patient's ability to perform ADL since drug may cause fatigue and lethargy.
  • Lab tests: Obtain periodic serum electrolytes, especially in older adults. Monitor lithium levels with concurrent administration of lithium and methazolamide.

Patient & Family Education

  • Be aware that drug may cause drowsiness. Advise caution with hazardous activities until response to drug is known.

Common adverse effects in italic, life-threatening effects underlined; generic names in bold; classifications in SMALL CAPS; Canadian drug name; Prototype drug

© 2006-2023 Last Updated On: 01/28/2023 (0)
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