If I where you I would carry Diamox (250 mg), Dexamethosone (2mg tablet or injection) for Cerebal Oedema, and Nifidipine (8mg from memory) (or Pulmonary Oedema. I am not a Dr but this is the advice I got from some UK mountaineering website and it seems consistant with other recommendations.
If you need to use them these are the rough guidelines. Once you are better and at a lower altitude get of the drugs ASAP as these are high doses.
DIAMOX
• 125 mg twice a day
DEXAMETHASONE
• 8mg initially then,
• 4mg every 6 hours
I was able to buy these drugs (and many others) over the counter in Nepal and Pakistan (not sure on China). I would recommend carrying these 3 and maybe some broard range anti-biotics.
I won't comment on taking Diamox as a preventative or waiting until you feel the effects - it would promote more debate than weather or not Arapiles should be retrobolted.