Diuretics and Carbonic Anhydrase Inhibitors

• Diuretics are classified by site of action, chemical structure, and potency.
• Diuretic potency is related to where they act in the nephron to inhibit sodium and water resorption.
• The more sodium and water inhibited from resorption, the greater the diuresis and potency.
• Loop diuretics are the most potent, followed by mannitol, metolazone, thiazides, and potassium-sparing diuretics.
• Diuretic drug types include carbonic anhydrase inhibitors, loop diuretics, osmotic diuretics, potassium-sparing diuretics, and thiazide and thiazide-like diuretics.

Carbonic Anhydrase Inhibitors

• Acetazolamide (Acetazolam®) is the most commonly used carbonic anhydrase inhibitor.
• It is available in oral and parenteral forms.
• Pregnant women could benefit from it's use despite potential fetal risks

Carbonic Anhydrase Inhibitors: Mechanism of Action

• Carbonic anhydrase inhibitors block carbonic anhydrase, preventing the exchange of H+ ions with sodium and water in the proximal tubules.
• Carbonic anhydrase helps make H+ ions available for exchange with sodium and water.
• Inhibition of carbonic anhydrase reduces H+ ion concentration in renal tubules.
• This leads to increased excretion of bicarbonate, sodium, water, and potassium.
• Water resorption decreases, and urine volume increases.

Carbonic Anhydrase Inhibitors: Indications

• They are used as adjunct drugs in the long-term management of open-angle glaucoma
• They are used as adjunct therapy for secondary glaucoma.
• They are used with miotics to lower intraocular pressure before ocular surgery.
• Other uses include the treatment of edema secondary to heart failure, high-altitude sickness, and epilepsy.

Carbonic Anhydrase Inhibitors: Contraindications

• Contraindications include known drug allergy.
• Contraindications include hyponatremia.
• Contraindications include hypokalemia.
• Contraindications include severe kidney or liver dysfunction.
• Contraindications include adrenal gland insufficiency and cirrhosis.

Carbonic Anhydrase Inhibitors: Adverse Effects

• Adverse effects include acidosis and hypokalemia.
• Other adverse effects include drowsiness, anorexia, and paresthesias.
• Further adverse effects include hematuria, urticaria, photosensitivity, and melena.

Carbonic Anhydrase Inhibitors: Interactions

• Concurrent use with digoxin may increase digoxin toxicity due to hypokalemia.
• Use with corticosteroids may also cause hypokalemia.
• Carbonic anhydrase inhibitors can increase the effects of amphetamines, carbamazepine, cyclosporine, phenytoin, and quinidine sulphate.