I would like to disagree with the assertion that Rainier is too low an altitude to warrant taking something for AMS.
I have been on Rainier 3 times by three different routes, and one of those times I developed a high altitude cough and shortness of breath at rest, so I took Diamox and rested an extra day at miur, and could climb much stronger the next day than on the previous two climbs.
It worked very quickly for me, and allowed me to recover within 12 hours to feeling better than I did on either of the previous climbs.