Diamox®
Acetazolamide · oral tablet
Antiglaucoma
Approved uses
Chronic simple (open-angle) glaucoma
250 mg to 1 g PO per 24 hours, in divided doses when the total exceeds 250 mg
Secondary glaucoma and preoperative acute angle-closure glaucoma
250 mg q4h; or an initial 500 mg followed by 125 mg or 250 mg q4h; some cases respond to 250 mg BID short-term
OFF-LABELNot in the FDA label for this product
Idiopathic intracranial hypertension with mild visual loss
Titrated to the maximally tolerated dosage, up to 4 g/day PO, added to a low-sodium weight-reduction diet, for 6 months (IIHTT regimen)
RCT · n=165 · modest benefit
Multicenter randomized, double-masked, placebo-controlled trial, N=165 (86 drug, 79 placebo), all on a low-sodium weight-reduction diet. Improvement in perimetric mean deviation was 1.43 dB versus 0.71 dB with placebo; the 0.71 dB difference has a 95% CI that reaches zero (0 to 1.43 dB, P=.050). Papilledema grade (treatment effect -0.70, 95% CI -0.99 to -0.41, P<.001) and NEI VFQ-25 vision-related quality of life (treatment effect 6.35, 95% CI 2.22 to 10.47, P=.003) improved more clearly. The authors call the visual field benefit modest and state that its clinical importance remains to be determined.
Chronic cystoid macular edema in retinitis pigmentosa
500 mg/day PO, the dose that outperformed 250 mg/day in the crossover trial below
Crossover · n=12 · low quality
Masked, placebo-controlled crossover trial in 12 patients treated in 2-week periods: 10 of 12 had both subjective and objective visual acuity improvement, 6 of 12 had less angiographic leakage, and 500 mg/day was more effective than 250 mg/day. A 2022 systematic review and meta-analysis (32 studies reviewed, 7 pooled) concluded that oral and topical carbonic anhydrase inhibitors and local steroids do reduce central macular thickness in this setting, but rated the overall quality of evidence poor because of inferior study designs and small patient numbers.
Contraindications
- Depressed serum sodium or potassium, marked kidney or liver disease or dysfunction, suprarenal gland failure, hyperchloremic acidosis.
- Cirrhosis, because of the risk of hepatic encephalopathy.
- Long-term administration in chronic non-congestive angle-closure glaucoma, where lowered IOP may mask worsening glaucoma while organic closure of the angle proceeds.
Available Forms250 mg tablets
Mechanism of ActionCarbonic anhydrase inhibitor: blocks the enzyme that catalyzes reversible hydration of carbon dioxide, and in the eye this decreases aqueous humor secretion and lowers IOP. Renal inhibition causes loss of bicarbonate, which carries out sodium, potassium, and water, alkalinizing the urine and promoting diuresis.
Warnings & Precautions
- Sulfonamide hypersensitivity: Fatalities have occurred, although rarely, from severe sulfonamide reactions; discontinue at the first sign of hypersensitivity or other serious reaction.
- Cross-sensitization: Sensitization may recur whenever any sulfonamide is readministered, irrespective of route.
- Hematologic monitoring: Baseline CBC and platelet count before starting and at regular intervals during therapy; discontinue early if significant changes occur.
- Serum electrolytes: Periodic monitoring recommended.
- High-dose aspirin: Concomitant use has caused anorexia, tachypnea, lethargy, coma, and death.
- Pulmonary obstruction or emphysema: Use with caution where alveolar ventilation may be impaired, since acidosis may be precipitated or aggravated.
- Dose escalation: Raising the dose does not increase diuresis, often decreases it, and may increase drowsiness and paresthesia.
Common Side Effects
- Ocular: Transient myopia, which invariably subsides on dose reduction or discontinuation.
- Systemic: Paresthesia, particularly tingling in the extremities, hearing dysfunction or tinnitus, loss of appetite, taste alteration, nausea, vomiting, diarrhea, polyuria, drowsiness, and confusion; most often early in therapy.
- Metabolic: Metabolic acidosis and electrolyte imbalance.
- Severe sulfonamide reactions: Stevens-Johnson syndrome, toxic epidermal necrolysis, fulminant hepatic necrosis, agranulocytosis, aplastic anemia, and other blood dyscrasias; rare, with fatalities reported.
- Other sulfonamide class reactions: Anaphylaxis, fever, rash including erythema multiforme, crystalluria, renal calculus, bone marrow depression, thrombocytopenic purpura, hemolytic anemia, leukopenia, pancytopenia, agranulocytosis.
Pregnancy & LactationPregnancy: Teratogenic (limb defects) in mice, rats, hamsters, and rabbits; no adequate and well-controlled studies in pregnant women; use only if the potential benefit justifies the potential risk to the fetus.
Lactation: Potential for serious adverse reactions in nursing infants; decide whether to discontinue nursing or the drug, weighing its importance to the mother.
Pediatric UseSafety and effectiveness in pediatric patients have not been established.