Diamox
"After several bird tours flirting with 10,000 - 11,000 ft elevation I became suspicious that I was  susceptible to alt. sickness.  A redirected flight to LaPaz, Bolivia (and some unscheduled ascents near Cochabamba) convinced me I was.  Typically I serve as a human altimeter, within minutes of reaching 11,000 ft I'm puking my guts out.

Diamox has been a wonder drug in preventing alt. sickness on tours I've been on since Bolivia.  I've travelled from 8,000 ft straight to 14,000 ft several times with no alt. sickness symptoms at all.  125 mg before bed is all I need.  Tingling and bad tasting soda symptoms are greatly reduced at that dosage compared to the 250mg I initially used."