Class: Carbonic anhydrase inhibitor
- Tablets 25 mg
- Tablets 50 mg
Inhibits carbonic anhydrase enzyme, reducing rate of aqueous humor secretion and, thus, lowering IOP.
Well absorbed from the GI tract, reaching peak plasma levels in 1 to 2 h. The C max for the 25, 50, and 100 mg twice daily dosing regiments are 2.5, 5.1, and 10.7 mcg/mL, respectively. The AUCs are 1,130, 2,571, and 5,418 mcg•min/mL, respectively.
Methazolamide is distributed throughout the body including plasma, cerebrospinal fluid, aqueous humor, RBC, bile, and extracellular fluid. The Vd ranges from 17 to 23 L. Approximately 55% is bound to plasma proteins.
Mean steady-state plasma elimination t ½ is about 14 h. Approximately 25% is recovered unchanged in the urine over the dosing interval and renal Cl accounts for 20% to 25% of the total Cl.
Decrease in IOP usually occurs in 2 to 4 h.
About 6 to 8 h.
About 10 to 18 h.
Indications and Usage
Treatment of ocular conditions where lowering IOP is likely to be of therapeutic benefit (eg, chronic open-angle glaucoma, secondary glaucoma, preoperatively in acute angle-closure glaucoma).
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 (may precipitate hepatic encephalopathy); long-term administration in patients with angle-closure glaucoma.
Dosage and AdministrationAdults
PO 50 to 100 mg twice daily or 3 times daily.
Drug InteractionsAspirin (high-dose)
Anorexia, tachypnea, lethargy, coma, and death have been reported.Steroids
Use with caution because of risk of developing hypokalemia.
Laboratory Test Interactions
None well documented.
Paresthesias; malaise; drowsiness; confusion; loss of appetite; convulsions.
Urticaria; Stevens-Johnson syndrome; toxic epidermal necrolysis.
Hearing dysfunction; tinnitus; transient myopia.
Taste alteration; GI disturbance (including nausea, vomiting, diarrhea); melena.
Polyuria; hematuria; glucosuria; crystalluria; renal calculi.
Agranulocytosis; aplastic anemia; other blood dyscrasias.
Hepatic insufficiency; fulminant hepatic necrosis.
Category C .
Safety and efficacy not established.
Patients with known sulfonamide sensitivity may show allergic reactions to methazolamide.
Use could precipitate hepatic coma.
Use in pulmonary obstruction and emphysema may aggravate or precipitate acidosis.
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