There is a certain amount of confusion over the optimal dosing regimen.

The trend for hikers has certainly trended towards a lower and lower amount over the last 20 years.

What is published in the actual package inserts of the medications is probably the original info, and it is probably related to helicoptor military operations, where you had people being inserted into higher altitudes in very short times, not hiking in.

One advantage of the lower dosing, is the freedom it gives with respect to the frequency. The manufacturer states:

"The dosage employed in the treatment of chronic simple (open-angle) glaucoma ranges from 250 mg to 1 g of acetazolamide per 24 hours, usually in divided doses for amounts over 250 mg."

So for doses of 250/day or less, it can be administered in a once a day dose, which is more convenient.

For the last couple of years, I've recommended, and used myself, a 1/2 tab of a 125 at bedtime (to maximize the impact on the disturbed breathing involved with AMS, probably the most commom form of AMS symptom, which is well known to be best treated with diamox)

As for onset and duration of treatment, the manufacturer also states:

Quote:
Acute Mountain Sickness: Dosage is 500 mg to 1000 mg daily, in divided doses. In circumstances of rapid ascent, such as in rescue or military operations, the higher dose level of 1000 mg is recommended. It is preferable to initiate dosing 24 to 48 hours before ascent and to continue for 48 hours while at high altitude, or longer as necessary to control symptoms.


And I think that is a good guideline to follow, with the one caveat:
if a person has never taken the medication before, I think it is a good idea to take a dose or two a few weeks before a trip to make sure that one will not have some sort of unusual or bizarre reaction, that would screw up one's trip!

Diamox does contain the molecule sulfa, but it is NOT the same as a sulfa antibiotic, and people who are allergic to sulfa antibiotics generally are not at greater risk of reactions, than any other people who get allergic reactions to things OTHER than sulfa. However, they should know this, and if considering taking Diamox, should take a dose in civilization, not out in the boondocks.

Also, the generic acetazolamide is every bit as good as the brand name Diamox.