From the Guidelines
Carbonic anhydrase inhibitors, such as acetazolamide, zonisamide, and topiramate, are used to treat various conditions, including obstructive sleep apnea, glaucoma, altitude sickness, epilepsy, and idiopathic intracranial hypertension. These medications work by blocking the enzyme carbonic anhydrase, which normally catalyzes the conversion of carbon dioxide and water to carbonic acid, leading to increased excretion of bicarbonate, sodium, and water, resulting in their therapeutic effects 1.
Key Uses of Carbonic Anhydrase Inhibitors
- Obstructive sleep apnea: acetazolamide, zonisamide, and topiramate have been shown to reduce sleep apnea intensity (AHI) by up to 45% in unselected groups of patients 1
- Glaucoma: carbonic anhydrase inhibitors, such as acetazolamide, methazolamide, dorzolamide, and brinzolamide, are used to reduce intraocular pressure by decreasing the production of aqueous humor in the eye
- Altitude sickness: acetazolamide is typically prescribed at 125-250mg twice daily starting 1-2 days before ascent
- Epilepsy: carbonic anhydrase inhibitors, such as acetazolamide and zonisamide, are used to treat certain forms of epilepsy
- Idiopathic intracranial hypertension: carbonic anhydrase inhibitors, such as acetazolamide, are used to treat this condition
Important Considerations
- Common side effects of carbonic anhydrase inhibitors include tingling in extremities, altered taste, fatigue, and potential kidney stones with long-term use
- These medications should be used cautiously in patients with sulfa allergies, as cross-reactivity can occur
- The dose range and treatment periods for carbonic anhydrase inhibitors vary widely, and patients should be closely monitored for efficacy and adverse effects 1
From the FDA Drug Label
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). Methazolamide is a potent inhibitor of carbonic anhydrase. Methazolamide’s inhibitory action on carbonic anhydrase decreases the secretion of aqueous humor and results in a decrease in intraocular pressure.
Carbonic Anhydrase Inhibitors are used for:
- Controlling fluid secretion in conditions like glaucoma
- Treating certain convulsive disorders such as epilepsy
- Promoting diuresis in cases of abnormal fluid retention, like cardiac edema Examples of carbonic anhydrase inhibitors include:
- Acetazolamide 2
- Methazolamide 3
From the Research
Carbonic Anhydrase Inhibitors
- Carbonic anhydrase inhibitors (CAIs) are a class of medications that have various applications, including the treatment of glaucoma, acute mountain sickness, and epilepsy 4, 5, 6.
- Examples of CAIs include:
- First generation CAIs: acetazolamide, methazolamide, and dichlorophenamide, which are used systemically for the management of glaucoma 4.
- Second generation CAIs: dorzolamide and brinzolamide, which are used topically as eye drops for the treatment of glaucoma with fewer side effects compared to first generation drugs 4, 7.
- CAIs can be used alone or in combination with other drugs, such as adrenergic agonist/antagonists or prostaglandin analogs, for the treatment of glaucoma 4, 7.
Applications of Carbonic Anhydrase Inhibitors
- Glaucoma: CAIs are used to lower intraocular pressure by reducing aqueous humour production 4, 7.
- Acute Mountain Sickness: acetazolamide, a CAI, is used to prevent or reduce symptoms of acute mountain sickness, including headache, nausea, fatigue, and poor sleep 5, 8.
- Epilepsy: acetazolamide is used as an antiepileptic agent, with a mechanism of action that involves the inhibition of carbonic anhydrase and the activation of acid-sensing ion channels 6.
Dosage and Efficacy
- The dosage of acetazolamide for the prevention and treatment of acute mountain sickness can vary, with doses of 500-750 mg/day appearing to be the most effective for minimizing symptoms 8.
- The efficacy of CAIs in the treatment of glaucoma and epilepsy has been demonstrated in various studies, with response rates and seizure-free rates varying depending on the specific medication and population being studied 4, 6, 7.