Methazolamide and acetazolamide in acute mountain sickness.

Methazolamide (150 mg/d) was as effective as acetazolamide (500 mg/d) in preventing the symptoms of acute mountain sickness in 20 subjects ascending to 4985 m. PaO2 and oxygen saturation levels were similar on the two drugs but the fall in PaCO2 was greater on acetazolamide. Paraesthesiae, a side-effect of carbonic anhydrase inhibitors, tended to be less at high altitude on methazolamide and was significantly less when taking 100 mg/d at low altitude. It is likely that paraesthesiae is similar on the two drugs when given in doses that affect blood gases equally.