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Prophylactic bosentan does not improve exercise capacity or lower pulmonary artery systolic pressure at high altitude.

Author(s): Seheult RD, Ruh K, Foster GP, Anholm JD

Affiliation(s): VA Loma Linda Healthcare System, Loma Linda, CA, United States; Department of Medicine, Division of Pulmonary & Critical Care Medicine, Loma Linda University, Loma Linda, CA, United States.

Publication date & source: 2008-10-11, Respir Physiol Neurobiol., [Epub ahead of print]

Hypoxic pulmonary vasoconstriction in response to high altitude ascent may contribute to decreased exercise capacity. Endothelin receptor antagonists reduce pulmonary artery pressure and improve exercise capacity in patients with pulmonary arterial hypertension, but their effects on exercise capacity at altitude are unknown. We studied the efficacy of bosentan started 5 days prior to ascent on exercise capacity and pulmonary artery systolic pressure (PASP) at 3800m altitude. Eight healthy subjects completed a double-blinded, randomized, placebo-controlled, crossover study. The end-points were time to complete a cycle ergometer time trial, PASP, and hemoglobin oxygen saturation (SpO(2)). The time to complete the time trial at altitude in subjects on placebo and bosentan was 527+/-159 and 525+/-156s respectively (P=0.90). PASP was not different on bosentan compared with placebo. Mean SpO(2) during the altitude time trial was lower in subjects taking bosentan compared to placebo (78+/-6 vs. 85+/-8% respectively, P=0.03). Bosentan initiated 5 days prior to ascent to high altitude did not improve exercise capacity or reduce PASP, and worsened SpO(2) during high intensity exercise at altitude.

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