Sildenafil increased exercise capacity during hypoxia at low altitudes and at Mount Everest base camp: a randomized, double-blind, placebo-controlled crossover trial

Clinical Trial

Hossein A Ghofrani et al. Ann Intern Med. 2004.

Abstract

Background: Alveolar hypoxia causes pulmonary hypertension and enhanced right ventricular afterload, which may impair exercise tolerance. The phosphodiesterase-5 inhibitor sildenafil has been reported to cause pulmonary vasodilatation.

Objective: To investigate the effects of sildenafil on exercise capacity under conditions of hypoxic pulmonary hypertension.

Design: Randomized, double-blind, placebo-controlled crossover study.

Setting: University Hospital Giessen, Giessen, Germany, and the base camp on Mount Everest.

Participants: 14 healthy mountaineers and trekkers.

Measurements: Systolic pulmonary artery pressure, cardiac output, and peripheral arterial oxygen saturation at rest and during assessment of maximum exercise capacity on cycle ergometry 1) while breathing a hypoxic gas mixture with 10% fraction of inspired oxygen at low altitude (Giessen) and 2) at high altitude (the Mount Everest base camp).

Intervention: Oral sildenafil, 50 mg, or placebo.

Results: At low altitude, acute hypoxia reduced arterial oxygen saturation to 72.0% (95% CI, 66.5% to 77.5%) at rest and 60.8% (CI, 56.0% to 64.5%) at maximum exercise capacity. Systolic pulmonary artery pressure increased from 30.5 mm Hg (CI, 26.0 to 35.0 mm Hg) at rest to 42.9 mm Hg (CI, 35.6 to 53.5 mm Hg) during exercise in participants taking placebo. Sildenafil, 50 mg, significantly increased arterial oxygen saturation during exercise (P = 0.005) and reduced systolic pulmonary artery pressure at rest (P < 0.001) and during exercise (P = 0.031). Of note, sildenafil increased maximum workload (172.5 W [CI, 147.5 to 200.0 W]) vs. 130.6 W [CI, 108.8 to 150.0 W]); P < 0.001) and maximum cardiac output (P < 0.001) compared with placebo. At high altitude, sildenafil had no effect on arterial oxygen saturation at rest and during exercise compared with placebo. However, sildenafil reduced systolic pulmonary artery pressure at rest (P = 0.003) and during exercise (P = 0.021) and increased maximum workload (P = 0.002) and cardiac output (P = 0.015). At high altitude, sildenafil exacerbated existing headache in 2 participants.

Limitations: The study did not examine the effects of sildenafil on normoxic exercise tolerance.

Conclusions: Sildenafil reduces hypoxic pulmonary hypertension at rest and during exercise while maintaining gas exchange and systemic blood pressure. To the authors' knowledge, sildenafil is the first drug shown to increase exercise capacity during severe hypoxia both at sea level and at high altitude.

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Comment in

Sildenafil for enhanced performance at high altitude?
Rubin LJ, Naeije R. Rubin LJ, et al. Ann Intern Med. 2004 Aug 3;141(3):233-5. doi: 10.7326/0003-4819-141-3-200408030-00016. Ann Intern Med. 2004. PMID: 15289224 No abstract available.
Summaries for patients. Sildenafil increases exercise capacity in low-oxygen settings.
[No authors listed] [No authors listed] Ann Intern Med. 2004 Aug 3;141(3):I12. doi: 10.7326/0003-4819-141-3-200408030-00001. Ann Intern Med. 2004. PMID: 15289233 No abstract available.

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Sildenafil increased exercise capacity during hypoxia at low altitudes and at Mount Everest base camp: a randomized, double-blind, placebo-controlled crossover trial - PubMed (original) (raw)