Just to be clear about Diamox (acetazolamide), it's only a mild diuretic (as is caffeine). The mechanism that makes Diamox work is to cause a shift in bicarbonate ions in the body that is related to respiration at higher elevations and respiratory alkalosis (changes in the acid-base balance in blood). More frequent urination as well as possible numbness/tingling of the lips and fingers are bonus side effects. Caffeine doesn't work like Diamox --- but it will give you a little extra buzz to help power you up the mountain.
