Diamox...when used as prescribed, works well for the high altitudes. Was not a believer until I tried it in Colorado for a stay at 9500 feet. (I am an annual visitor there and always wondered why I felt awful during the first day or two. It was not until I planned my trip to Peru for April 2020-CANCELLED that I discovered Diamox.) And as I understand it, Diamox is available OTC in Peru, whereas the US requires a prescription.