ReviewCan sildenafil improve physical performance at altitude? Current scientific evidence¿Afecta sidenafilo a la capacidad física en altitud? Evidencias científicas en la actualidad
Section snippets
Mechanism of sildenafil action
Since the work of Ghofrani et al.1 about the improvement of physical capacity during exercise in hypoxia conditions due to the use of sildenafil,1 several studies have attempted to reproduce their findings. However, to date, there is still controversy over whether phosphodiesterase type 5 (PDE-5) inhibitor is a substance that can actually improve performance under hypoxic conditions. Sildenafil has been used to treat erectile dysfunction2 through inhibition of PDE-5 activity which, in turn,
Hypoxia and exercise
Exposure to acute hypoxia (AH) causes the reduction of the maximum aerobic capacity, directly affecting the exercise performance.14, 15, 16 VO2max tends to diminish in direct proportion to the decrease in CaO2, which occurs as hypoxia increases.17, 18 Exercise exacerbates CaO2 reduction due to the lower uptake of O2 during gas exchanging in the lungs,1, 19 which may increase the risk of pulmonary edema,11, 20 especially in people predisposed to suffer this complications associated to rapid
Sildenafil effects during exercise and hypoxia
Research conducted on healthy people, combining the effects of exercise and hypoxia after sildenafil administration, has yielded contrasting results. Studies on this subject present a wide range of designs and methodologies leaving many questions still unanswered about the possible benefits of the sildenafil administration under hypoxic conditions. The following paragraphs present a review of the most relevant studies on sildenafil administration and exercise in hypoxia. All the studies had a
Normobaric versus hypobaric hypoxia
An important point to keep in mind when comparing all the cited reports it is to consider the difference in the hypoxia conditions (simulated or natural) and the type of hypoxia (normobaric or hypobaric) that subjects underwent, because some studies showed differences between exposition to normobaric and hypobaric hypoxia.35, 36, 37, 38, 39 Comparing both types of hypoxia, one study described that hypobaric hypoxia leads to greater hypoxemia, hypocapnia, alkalosis and lower blood SaO2 than
Conclusions
Due that initial research on the effects of sildenafil on pulmonary circulation were conducted in patients with cardiopulmonary disease, it was possible to early confirm that sildenafil is an effective vasodilator of the pulmonary arteries also in healthy people, whether in the hypobaric hypoxia or under normobaric conditions.1, 14, 29, 30
However, it has been ruled out any performance improvement under normoxic conditions after sildenafil administration. Those, the use of sildenafil as an
Conflict of interest
The authors manifest that they have NO affiliations with or involvement in any organization or entity with any financial interest (such as honoraria; educational grants; participation in speakers’ bureaus; membership, employment, consultancies, stock ownership, or other equity interest; and expert testimony or patent-licensing arrangements), or non-financial interest (such as personal or professional relationships, affiliations, knowledge or beliefs) in the subject matter or materials discussed
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