Four randomised studies have investigated G. biloba as prophylactic treatment against altitude sickness, producing mixed results (Chow et al 2005, Gertsch et al 2002, 2004, Roncin et al 1996). One study involving 44 subjects found that a dose of 160 mg/day taken for 5 days as prophylactic treatment resulted in no subject developing the cerebral symptoms of acute mountain sickness versus 41 % of subjects in the placebo group. Whereas only three subjects (13.6%) in the EGb 761 group developed respiratory symptoms of acute mountain sickness, 18 (81.8%) in the placebo group developed these symptoms. Besides effectively preventing mountain sickness for moderate altitude (5400 m), treatment also decreased vasomotor disorders of the extremities (Roncin et al 1996). A second study showed that G. biloba 180 mg/day started 24 hours before rapid ascent from sea level to 4205 m significantly reduced altitude sickness under double-blind test conditions (Gertsch et al 2002). The two more recent studies compared ginkgo to placebo and acetazolamide and found no significant effects for ginkgo (Chow et al 2005, Gertsch et al 2004). The largest study was conducted by Gertsch et al and involved 487 healthy Western hikers. It compared the effects of ginkgo, acetazolamide (250 mg), combined acetazolamide and ginkgo, and placebo. Participants took at least 3-4 doses before ascent above 4000 m in the Nepal Himalayas. The incidence of acute mountain sickness was 34% for placebo, 12% for acetazolamide, 35% for ginkgo and 14% for combined ginkgo and acetazolamide. Chow et al conducted a smaller study of 57 healthy unacclimatised subjects using a randomised, placebo-controlled design. Subjects were taken to an elevation of 3800 m within 24 hours, with acetazolamide producing significantly better effects than ginkgo or placebo using the Lake Louise Acute Mountain Sickness Scoring System. Subjects receiving ginkgo were as likely as placebo to experience acute mountain sickness whereas acetazolamide was protec-
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