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Randomised, double blind, placebo controlled comparison of ginkgo biloba and acetazolamide for prevention of acute mountain sickness among Himalayan trekkers: the prevention of high altitude illness trial (PHAIT)

BMJ 2004; 328 doi: (Published 01 April 2004) Cite this as: BMJ 2004;328:797
  1. Jeffrey H Gertsch (jeffgertsch{at}, house officer1,
  2. Buddha Basnyat, medical director2,
  3. E William Johnson, house officer3,
  4. Janet Onopa, assistant professor of medicine4,
  5. Peter S Holck Prevention of High Altitude Illness Trial Research Group, associate professor of biostatistics4
  1. 1Department of Internal Medicine, Maricopa Medical Center, 2601 E Roosevelt Avenue number O-D-10, Phoenix, AZ 85008, USA
  2. 2Himalayan Rescue Association, Kathmandu, Nepal
  3. 3University of Washington School of Medicine, Seattle, WA 98195-6410, USA
  4. 4University of Hawaii, John A Burns School of Medicine, Honolulu, Hawaii, USA
  1. Correspondence to: J H Gertsch
  • Accepted 23 January 2004


Objective To evaluate the efficacy of ginkgo biloba, acetazolamide, and their combination as prophylaxis against acute mountain sickness.

Design Prospective, double blind, randomised, placebo controlled trial.

Setting Approach to Mount Everest base camp in the Nepal Himalayas at 4280 m or 4358 m and study end point at 4928 m during October and November 2002.

Participants 614 healthy western trekkers (487 completed the trial) assigned to receive ginkgo, acetazolamide, combined acetazolamide and ginkgo, or placebo, initially taking at least three or four doses before continued ascent.

Main outcome measures Incidence measured by Lake Louise acute mountain sickness score ≥ 3 with headache and one other symptom. Secondary outcome measures included blood oxygen content, severity of syndrome (Lake Louise scores ≥ 5), incidence of headache, and severity of headache.

Results Ginkgo was not significantly different from placebo for any outcome; however participants in the acetazolamide group showed significant levels of protection. The incidence of acute mountain sickness was 34% for placebo, 12% for acetazolamide (odds ratio 3.76, 95% confidence interval 1.91 to 7.39, number needed to treat 4), 35% for ginkgo (0.95, 0.56 to 1.62), and 14% for combined ginkgo and acetazolamide (3.04, 1.62 to 5.69). The proportion of patients with increased severity of acute mountain sickness was 18% for placebo, 3% for acetazoalmide (6.46, 2.15 to 19.40, number needed to treat 7), 18% for ginkgo (1, 0.52 to 1.90), and 7% for combined ginkgo and acetazolamide (2.95, 1.30 to 6.70).

Conclusions When compared with placebo, ginkgo is not effective at preventing acute mountain sickness. Acetazolamide 250 mg twice daily afforded robust protection against symptoms of acute mountain sickness.


  • Contributors JHG wrote the original manuscript with the close consultation of the authors; he will act as guarantor for the paper. The guarantor accepts full responsibility for the conduct of the study, had access to the data, and controlled the decision to publish. All authors were responsible for the study design with end stage input from BM Cogtry, AE Derrow, DJ Douglas, JY Meyer, AR Mulcahy, JD Ngo, CT Purgason, SG Seale, JL Snow, and H Zacharia. JO and JHG acquired the funding. JHG, BB, BM Cogtry, AE Derrow, DJ Douglas, JY Meyer, AR Mulcahy, JD Ngo, CT Purgason, SG Seale, JL Snow, and H Zacharia were responsible for the implementation of the study and data collection. JHG, BB, EWJ, JO, and PSH were responsible for data entry and analysis. JHG, BB, EWJ, JO, PSH, BM Cogtry, AE Derrow, DJ Douglas, JY Meyer, AR Mulcahy, JD Ngo, CT Purgason, SG Seale, JL Snow, and H Zacharia prepared and revised the manuscript.

  • Funding Pharmaton provided financial support for study expenses. Representatives of Pharmaton provided limited statistical support by generating the power calculation.

  • Competing interests JHG and JO have been funded by Pharmaton to attend a research symposium. All authors except BB, EWJ, JO, and PSH have received reimbursement for on-site living costs incurred during the implementation period of the study.

  • Ethical approval This study was conducted under the auspices of the Himalayan Rescue Association and received ethical approval from the Nepal Health Research Council.

  • Accepted 23 January 2004
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