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Acetazolamide (Acetazolamide) - Description and Clinical Pharmacology

 
 



AcetaZOLAMIDE TABLETS USP

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DESCRIPTION

AcetaZOLAMIDE, an inhibitor of the enzyme carbonic anhydrase is a white to faintly yellowish white, crystalline, odorless powder, weakly acidic, very slightly soluble in water and slightly soluble in alcohol. The chemical name for AcetaZOLAMIDE is N - (5-Sulfamoyl- 1,3,4-thiadiazol-2-y1)-acetamide and has the following structural formula:

Each tablet, for oral administration, contains 125 mg or 250 mg of AcetaZOLAMIDE and the following inactive ingredients: croscarmellose sodium, magnesium stearate, microcrystalline cellulose, pregelatinized starch, sodium lauryl sulfate.

CLINICAL PHARMACOLOGY

AcetaZOLAMIDE is a potent carbonic anhydrase inhibitor, effective in the control of fluid secretion (e.g., some types of glaucoma), in the treatment of certain convulsive disorders (e.g., epilepsy) and in the promotion of diuresis in instances of abnormal fluid retention (e.g., cardiac edema).

AcetaZOLAMIDE is not a mercurial diuretic. Rather, it is a nonbacteriostatic sulfonamide possessing a chemical structure and pharmacological activity distinctly different from the bacteriostatic sulfonamides.

AcetaZOLAMIDE is an enzyme inhibitor that acts specifically on carbonic anhydrase, the enzyme that catalyzes the reversible reaction involving the hydration of carbon dioxide and the dehydration of carbonic acid. In the eye, this inhibitory action of AcetaZOLAMIDE decreases the secretion of aqueous humor and results in a drop in intraocular pressure, a reaction considered desirable in cases of glaucoma and even in certain nonglaucomatous conditions. Evidence seems to indicate that AcetaZOLAMIDE has utility as an adjuvant in the treatment of certain dysfunctions of the central nervous system (e.g., epilepsy). Inhibition of carbonic anhydrase in this area appears to retard abnormal, paroxysmal, excessive discharge from central nervous system neurons. The diuretic effect of AcetaZOLAMIDE is due to its action in the kidney on the reversible reaction involving hydration of carbon dioxide and dehydration of carbonic acid. The result is renal loss of HCO3 ion, which carries out sodium, water, and potassium. Alkalinization of the urine and promotion of diuresis are thus effected. Alteration in ammonia metabolism occurs due to increased reabsorption of ammonia by the renal tubules as a result of urinary alkalinization.

Placebo-controlled clinical trials have shown that prophylactic administration of AcetaZOLAMIDE at a dose of 250 mg every eight to 12 hours (or a 500 mg controlled-release capsule once daily) before and during rapid ascent to altitude results in fewer and/or less severe symptoms (such as headache, nausea, shortness of breath, dizziness, drowsiness and fatigue) of acute mountain sickness (AMS). Pulmonary function (e.g., minute ventilation, expired vital capacity, and peak flow) is greater in the AcetaZOLAMIDE treated group, both in subjects with AMS and asymptomatic subjects. The AcetaZOLAMIDE treated climbers also had less difficulty in sleeping.

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