To adapt to altitude, one needs to breathe more frequently during ascent to make up for the thinning air. What Diamox does is it increases the respiratory rate, speeding up acclimatization. The manufacturer of Diamox states that in their tests, “pulmonary function (e.g., minute ventilation, expired vital capacity, and peak flow) is greater in the acetazolamide treated group, both in subjects with AMS and asymptomatic subjects. The acetazolamide treated climbers also had less difficulty sleeping.”
What the manufacturer recommends it that it be used as a preventative measure, where you would take it 24-28 hours prior to rapid ascent, and throughout your climb (until descent). But some use it as a treatment, taking it only when symptoms of AMS arise.
Most people ignore this advice, but if one plans to possibly use Diamox on the climb, it is important that he/she should take a dosage for a day or two while in the comfort of their home to see what the effects are. There are some side effects (tingling hands, increased urination, hearing loss, taste loss, upset stomach, vomiting, confusion) to taking the drug, so one should be sure their body doesn’t have an adverse reaction before getting on the mountain with it. As you can see, some of those side effects can easily be confused with AMS.
Diamox is used for other purposes, like treating glaucoma, epilepsy and fluid retention. So who knows what else these chemicals may be doing to the body besides “increasing pulmonary function.” One should not take a drug without considering all the consequences, whether good or bad. And that’s why I neither recommend it nor do I discourage it… it’s up to the climber, based on their beliefs and hopefully based on information.