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Sildenafil does not reliably improve exercise performance in hypoxia: a systematic review
  1. Eric Alexander Carter1,
  2. Keith Lohse2,
  3. William Sheel1,
  4. Michael Koehle1,3
  1. 1Kinesiology, University of British Columbia, Vancouver, British Columbia, Canada
  2. 2Health-Kinesiology-Recreation, University of Utah, Salt Lake City, Utah, USA
  3. 3Division of Sports Medicine, University of British Columbia, Vancouver, British Columbia, Canada
  1. Correspondence to Dr Michael Koehle; michael.koehle{at}


Objective Sildenafil is a pulmonary vasodilator that may reduce the decrement in endurance performance in moderate hypoxia. We assessed the efficacy of sildenafil to improve performance in hypoxia.

Data sources/eligibility Criteria We systematically searched electronic databases (until August 2018) for randomised trials comparing sildenafil with placebo. We also examined the effect of sildenafil on pulmonary artery pressure (PAP), cardiac output (CO) and pulse oxygen saturation (SPO2) compared with placebo in hypoxia. Fourteen studies were included; 210 subjects received sildenafil 40, 50 or 100 mg/day.

Results Sildenafil showed a large effect for decreasing PAP during exercise and at rest, a small effect for increasing CO during exercise and a moderate effect at rest, a moderate effect for increasing SPO2 and a small effect for improving performance. In a subgroup analysis, there was no statistically significant difference between 100 and 50 mg sildenafil dose on SPO2. Sildenafil had a moderate effect on increasing SPO2 and performance at terrestrial hypobaric altitude but only a small effect on both in normobaric hypoxia. Regression analysis showed that hypoxic dose (PO2) and metabolic rate do not account for a significant portion of the variance in effect size for sildenafil on PAP, CO, SPO2 and performance.

Conclusion This meta-analysis indicates that sildenafil reduces PAP, has a moderate to small effect on CO and SPO2, and no effect on performance.

  • altitude
  • exercise physiology
  • physiology
  • pulmonary
  • performance

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  • Contributors EAC was responsible for conception of the meta-analysis, data collection, statistical analysis and preparation of the manuscript. KL assisted with conception of the meta-analysis, statistical analysis and manuscript preparation. WS assisted with conception of the meta-analysis and manuscript preparation. MK assisted with conception of the meta-analysis, statistical analysis and manuscript preparation. All coauthors have reviewed and approved the manuscript.

  • Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.

  • Competing interests None declared.

  • Patient consent for publication Not required.

  • Provenance and peer review Not commissioned; internally peer reviewed.