acetazolamide
Brand: Diamox
Prototype Drug
Drug Class: carbonic anhydrase inhibitor
Drug Family: diuretic
Subclass: sulfonamide CA inhibitor
Organ Systems: renalcns
Mechanism of Action
Inhibits carbonic anhydrase preventing bicarbonate reabsorption in proximal tubule causing NaHCO3 diuresis and metabolic acidosis; reduces aqueous humor production; reduces CSF production.
carbonic anhydrase (type II — renal tubule, eye, brain)
Indications
- altitude sickness prophylaxis
- open-angle glaucoma
- idiopathic intracranial hypertension
- metabolic alkalosis (adjunct)
- epilepsy (adjunct)
- central sleep apnea
- edema (weak, rarely used)
Contraindications
- sulfonamide allergy
- severe renal/hepatic impairment
- hypokalemia (risk)
- adrenal insufficiency
Adverse Effects
Common
- metabolic acidosis
- hypokalemia
- paresthesias (tingling extremities — common)
- GI upset
- polyuria
- taste change (carbonated beverages taste flat)
Serious
- aplastic anemia (rare)
- severe metabolic acidosis
- renal stones (alkaline urine — calcium phosphate)
Pharmacokinetics (ADME)
| Absorption | ~100% oral |
| Distribution | moderate |
| Metabolism | not significantly metabolized |
| Excretion | renal unchanged |
| Half-life | 2.4-5.8 hours |
| Onset | 1-3 hours |
| Peak | 1-4 hours |
| Duration | 8-12 hours |
| Protein Binding | 95% |
| Vd | moderate |
Drug Interactions
| Drug / Agent | Mechanism | Severity |
|---|---|---|
| lithium | diuresis may reduce lithium levels | moderate |
| topiramate/zonisamide | additive metabolic acidosis and kidney stone risk | major |
Nursing Considerations
- Monitor electrolytes (especially K+ and HCO3-)
- Altitude sickness: start 24-48h before ascent; continue 2 days at altitude
- Tingling in extremities is common and benign — often improves with time
- Sparkling water tastes flat (CA in taste buds blocked)
- Renal stones: ensure adequate hydration; alkaline urine predisposes to calcium phosphate stones
Clinical Pearls
- Metabolic acidosis is the intended effect: alkaline diuresis treats metabolic alkalosis; but creates alkaline urine
- Altitude sickness mechanism: increases respiratory drive by creating mild metabolic acidosis (normalizes chemoreceptor sensitivity to hypoxia)
Safety Profile
Pregnancy use-with-caution
Lactation use-with-caution
Renal Adjustment Required
Hepatic Adjustment Required
TDM Not required
Concordance Terms
Cross-referenced clinical concepts — click any term to see all content where it appears.