My cabin is in the CO Rockies at an 11,000 elevation. I took it as prescribed, 2 days before reaching altitude. Be sure to hydrate!...you can't drink enough water!
It directs you to dose the whole time you're at altitude but I took it for 2 weeks, then took a half dose for another week, then stopped all together. Was very happy that I didn't have the headaches or wake up in the middle of the night anxious.
OH,...it helps not to consume alcohol for a while til your body acclimates. If you do consume, be sure to hydrate even more!!