Acetazolamide reduces the erythropoietin response to hypoxia at high altitude in humans

Objective Acetazolamide, a carbonic anhydrase inhibitor, is often used as a prophylactic drug for acute mountain sickness. It may interfere with erythropoietin production due to its action on ventilation and renal function. Design A randomized, double-blind, placebo-controlled trial with 2 × 250 mg acetazolamide daily beginning one day before ascent from 590 m to 4559 m. Setting High-altitude research facilities at the Capanna Regina Margherita (Italy) at an altitude of 4559 m. Participants Eighteen healthy volunteers, aged 24–42 years. Main outcome measure: Plasma erythropoietin was measured by radioimmunoassay before and after the ascent. Results The increase of erythropoietin at high altitude was smaller in the acetazolamide group (increase by 10.8 ± 7.8 U/L or 58%) than in the placebo group (increase by 22.7 ± 13.8 U/L or 113%, p < .01). Conclusion Acetazolamide reduces the erythropoietin response to hypoxia in humans, which might also have therapeutic implications in conditions such as secondary polycythemia.