Tadalafil and acetazolamide versus acetazolamide for the prevention of severe high-altitude illness.

We report an open-label study comparing tadalafil and acetazolamide (n = 24) versus acetazolamide (n = 27) for prevention of high-altitude illness (HAI) at Mt. Kilimanjaro. Tadalafil group had lower rates of severe HAI compared with controls (4% vs 26%, p = 0.03), mostly because of decreased high-altitude pulmonary edema rates (4% vs 22%, p = 0.06).