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Diamox (Acetazolamide) - Description and Clinical Pharmacology

 
 



Rx only

Revised APRIL 2005

1007542503

Description

DIAMOX SEQUELS (Acetazolamide Extended-Release Capsules) are an inhibitor of the enzyme carbonic anhydrase.

DIAMOX 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 DIAMOX is N-(5-Sulfamoyl-1,3, 4-thiadiazol-2-yl) acetamide and has the following chemical structure:

MW 222.24          C<sub>4</sub>H<sub>6</sub>N<sub>4</sub>O<sub>3</sub>S<sub>2</sub>

MW 222.24 C4H6N4O3S2

DIAMOX SEQUELS are extended-release capsules, for oral administration, each containing 500 mg of acetazolamide and the following inactive ingredients:

Microcrystalline cellulose, sodium lauryl sulfate and talc.

The ingredients in the capsule shell are D&C red no. 28, D&C yellow no. 10, FD&C red no. 40, gelatin and titanium dioxide.

The ingredients in the imprinting ink are D&C yellow no. 10 aluminum lake, FD&C blue no. 1 aluminum lake, FD&C blue no. 2 aluminum lake, FD&C red no. 40 aluminum lake, pharmaceutical glaze, propylene glycol and synthetic iron oxide.

Clinical Pharmacology

DIAMOX 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).

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

DIAMOX 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 non-glaucomatous conditions. Evidence seems to indicate that DIAMOX has utility as an adjuvant in 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 DIAMOX 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 affected. Alteration in ammonia metabolism occurs due to increased reabsorption of ammonia by the renal tubules as a result of urinary alkalinization.

DIAMOX SEQUELS provide prolonged action to inhibit aqueous humor secretion for 18 to 24 hours after each dose, whereas tablets act for only eight to 12 hours. The prolonged continuous effect of SEQUELS permits a reduction in dosage frequency.

Plasma concentrations of acetazolamide peak from three to six hours after administration of DIAMOX SEQUELS, compared to one to four hours with tablets. Food does not affect bioavailability of DIAMOX SEQUELS.

Placebo-controlled clinical trials have shown that prophylactic administration of DIAMOX 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 of acute mountain sickness (AMS) such as headache, nausea, shortness of breath, dizziness, drowsiness, and fatigue. Pulmonary function (e.g., minute ventilation, expired vital capacity, and peak flow) is greater in the DIAMOX treated group, both in subjects with AMS and asymptomatic subjects. The DIAMOX treated climbers also had less difficulty in sleeping.

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