heathfield there is NOTHING in that link that says that medication stops working on planes. Factors mentioned are stress, dry air, changes of time zone, lower air pressure and lower oxygen content (which may potentiate medicine). In any case, would be careful about taking notice of what that website says. It may say that its "not for Profit" but it has a shop (which by the way in not accessible because of a broken link) and an ebay shop which no longer exists either. The statements are made with no reference to any research or reliable medical journals. If they said that the sky was blue, i would go out and check before believing them.