Acetazolamide

Description

Acetazolamide is a white to faintly yellowish-white, crystalline, odorless powder that is weakly acidic. Acetazolamide is supplied as a sterile powder, requiring reconstitution for intravenous use, as a bulk solution, and as capsules and tablets.

Acetazolamide is nonbacteriostatic sulfonamide, possessing a chemical structure and pharmacological activity distinctly different from bacteriostatic sulfonamides.

Research indicates that Acetazolamide is useful in the treatment of certain dysfunctions of the central nervous system that may lead to attacks of paralysis and muscle weakness.

Usage

Acetazolamide acts as a potent carbonic anhydrase inhibitor that is effective in control of fluid secretion. In the eye, this inhibitory action decreases the secretion of aqueous humor and results in a drop in intraocular pressure, making it useful in treatment of glaucoma in horses.

Acetazolamide has been found to be more effective than hydrochlorothiazide in controlling clinical signs of hyperkalemic periodic paralysis. This condition causes attacks of muscle weakness, stiffness, and, sometimes, muscle pain and irregular heartbeat in horses.

Acetazolamide is effective as a diuretic in cases of abnormal fluid retention. The diuretic effect of acetazolamide is due to its action in the kidney, resulting in renal loss of sodium, water, and potassium, leading to alkalinization of urine and promotion of diuresis in horses.

Acetazolamide is also used as an adjunctive treatment of edema due to congestive heart failure.

Dosage and Administration

Dosage and administration should be according to veterinarian's instructions. Each 500 mg vial should be reconsituted with at least 5 ml of sterile water for injection prior to use.

The direct intravenous route of administration is preferred. Intramuscular administration is not recommended. Read and follow manufacturer's directions provided with product.

Available forms: tablets: 125 and 250 mg; capsules: 500 mg; Injection 500 mg per vial; powder: 500 mg for reconsitution.

Side Effects

Acetazolamide may cause fatigue, drowsiness, fever, pain at injection site, gastrointestinal disturbances, blood dyscrasias, abnormal liver function, electrolyte imbalances, ataxia, convulsions, hearing disturbances, and myopia. Long term therapy may cause renal failure and increased risk of nephrolithiasis.

Precautions

Although rare, fatalities have occurred with use of acetazolamide, due to severe reactions to sulfonamides. If signs of hypersensitivity or other serious reactions occur, discontinue use of the drug.

Caution is advised when used with high-dose aspirin because of possibility of anorexia, tachypnea, lethargy, coma, and death.

Acetazolamide for injection may decrease serum concentrations of primidone.

Because of possible additive effects with other carbonic anhydrase inhibitors, concomitant use is not advisable.

Acetazolamide is not for use in pregnant mares.

Acetazolamide is FDA-approved for use in horses and is a prescription drug restricted to use by or on the lawful written or oral order of a licensed veterinarian.

Acetazolamide is a forbidden substance under AHSA and should not be used in competition horses. Check with appropriate regulatory group for rules and regulations.

Interactions

Acetazolamide and sodium bicarbonate used concurrently increases the risk of renal calculus formation.

Acetazolamide should not be used with high-dose aspirin therapy.

Acetazolamide may increase the effects of other folic acid antagonists.

Acetazolamide may increase or decrease blood glucose levels and care should be taken in horses being treated with antidiabetic agents.

Acetazolamide reduces urinary excretion of quinidine and may enhance its effect.

Acetazolamide may elevate cyclosporine levels.

Overdose

No specific antidote is known. Treatment should be symptomatic and supportive. Supportive measures are required to restore electrolyte and pH balance. The acidotic state can usually be corrected by administration of bicarbonate.

Acetazolamide may be dialyzable. This may be important in management of acetazolamide overdosage when complicated by renal failure.