Trekking and mountain climbing are quickly growing in popularity, but one of the challenges that climbers face is acute mountain sickness (AMS). Previous studies have shown that ibuprofen is an effective way to reduce the risk of AMS. Investigators wanted to find out if acetaminophen, a commonly used anti-pain medicine like ibuprofen, would have a comparable effect. They found almost no difference in the performance of both drugs, suggesting that acetaminophen may be another effective prophylactic treatment for AMS.