Acetazolamide: A Carbonic Anhydrase Inhibitor Drug

Acetazolamide

Acetazolamide is a carbonic anhydrase inhibitor drug that is used to treat a variety of conditions, primarily glaucoma and epilepsy. It works by inhibiting carbonic anhydrase, an enzyme that helps regulate fluid balance in the body. This inhibition leads to several effects, depending on the condition being treated.

How Does it Work?

It specifically inhibits carbonic anhydrase II and carbonic anhydrase IV. Carbonic anhydrases are a group of metalloenzymes that catalyze the reversible hydration of carbon dioxide. They play an important role in various physiological and biochemical processes related to fluid balance and electrolyte metabolism.

In glaucoma treatment, Acetazolamide works by reducing fluid secretion in the ciliary processes within the eye, thereby decreasing intraocular pressure. It makes the aqueous humor less acidic, increasing its diameter and lowering resistance to outflow. Both actions contribute to decreased pressure within the eye.

For seizure disorders and epilepsy, it is thought to work centrally in the brain to stabilize neuronal excitability. It causes metabolic acidosis by interfering with bicarbonate reabsorption in the kidneys. The resultant respiratory compensation elevates arterial pH and favors an increase in brain GABA levels and decrease in excitatory activity.

Uses and Indications

Glaucoma: It is commonly prescribed to treat chronic open-angle glaucoma and ocular hypertension as an adjunct to other medications or surgery when additional IOP reduction is needed. It can be used short-term pre- and post-operatively as well.

Epilepsy: As an add-on therapy, it is effective for treating partial seizures, especially in idiopathic generalized epilepsy syndromes. Limited evidence also supports its use in infantile spasms.

Mountaineering: For prevention of acute mountain sickness during rapid ascent to high altitudes, acetazolamide forces the respiratory system to acclimate more quickly.

Other uses: It finds niche applications in fluid management for congestive heart failure and liver disease. Periodic application is also effective for treating idiopathic intracranial hypertension.

Dosage and Administration

The usual oral adult dosage of acetazolamide is 250 mg twice daily for glaucoma and epilepsy. For mountain sickness prophylaxis, it is 125-250 mg twice daily, started 1-2 days before ascent and continued for the first 1-3 days at high altitudes.

The tablet or extended-release capsule can be taken with or without food. For pediatric use, the daily dosing is weight-based between 15-20 mg/kg. It takes 3-7 days for the full therapeutic effect to be achieved. Treatment duration depends on the condition but long-term use may be required to sustain response.

Side Effects and Precautions

Common side effects include paresthesia (tingling), fatigue, nausea, diarrhea, loss of appetite, and non-progressive metabolic acidosis. Serious complications are rare but electrolyte imbalance can rarely occur.

People with hepatic or renal impairment require dosage adjustment. Use caution with sulfonamide allergy due to cross-sensitivity. Monitor for ocular effects like myopia or blurred vision. Discontinue use if rash develops.

Drug Interactions

It can interact with other carbonic anhydrase inhibitors or with drugs that are excreted renally like lithium, which may require dosage adjustment. Concurrent use of high-dose aspirin or nonsteroidal anti-inflammatory drugs increases risk of metabolic acidosis.

Acetazolamide is a carbonic anhydrase inhibitor primarily used for the treatment of glaucoma and epilepsy due to its effects on fluid balance and neuronal excitability. While common side effects exist, it provides effective management when used judiciously for the approved indications under medical guidance. Ongoing research continues to explore additional applications of this versatile diuretic drug.

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