Nephrology · USMLE Step 1 and Step 2

Carbonic Anhydrase Inhibitors song

Acetazolamide - Mechanism & Side Effects, as a song. Hear the short teaser here. The full song is on YouTube and Spotify.

Carbonic Anhydrase Inhibitors

Full song on YouTube ↗Spotify ↗

Key points in this song10

Acetazolamide inhibits carbonic anhydrase, blocking the conversion of CO₂ + H₂O → H₂CO₃, reducing HCO₃⁻ reabsorption in the proximal tubule and causing a non-anion gap hyperchloremic metabolic acidosis.
Because acetazolamide wastes HCO₃⁻ in the urine, the urine becomes alkaline while the blood becomes acidic — a classic USMLE distinguishing feature.
Acetazolamide is first-line for acute mountain sickness (high-altitude illness) by stimulating ventilation through metabolic acidosis, which drives compensatory hyperventilation.
Used in the treatment of idiopathic intracranial hypertension (pseudotumor cerebri) by decreasing CSF production, which depends on carbonic anhydrase activity in the choroid plexus.
Acetazolamide is used in open-angle glaucoma to reduce aqueous humor production and lower intraocular pressure; it is not used for angle-closure glaucoma acutely as a standalone agent.
Classic adverse effects include paresthesias (tingling in extremities), sulfa hypersensitivity reactions, nephrolithiasis (calcium phosphate stones due to alkaline urine and hypercalciuria), and hypokalemia.
Acetazolamide is contraindicated in patients with sulfa allergy, severe hepatic disease (relies on urinary alkalinization to excrete NH₄⁺), and pre-existing hypokalemia or metabolic acidosis.
Used as adjunct therapy for absence seizures and as prophylaxis for periodic paralysis (hypokalemic and hyperkalemic forms) by altering membrane excitability through acid-base shifts.
The metabolic acidosis induced by acetazolamide causes a compensatory respiratory alkalosis shift — making it useful in correcting altitude-induced respiratory alkalosis paradoxically by re-acidifying plasma.
Acetazolamide belongs to the sulfonamide class; cross-reactivity with other sulfa drugs (sulfonamide antibiotics, thiazides, loop diuretics) is a tested USMLE association for allergic reactions.