This study was designed to bring together elements of prior studies and go one step further for definitive data on several points. The trial will employ two pharmaceutical intervention arms, which will compare placebo (the standard of care - information on prevention of altitude sickness) with the widely used NSAID ibuprofen. We will also determine Optic Nerve Sheath Diameter (ONSD) measurements via ultrasound in both the control and interventional arms. We will accomplish these objectives with a prospective, double blinded view of a large population of hikers who are ascending at their own rate in a true hiking environment: The White Mountain Research Station Owen Valley Lab (OVL) and Bancroft Station (BAR).