Sildenafil Increases Exercise Capacity in Low-Oxygen Settings. Ann Intern Med. 2004;141:I-12. doi: 10.7326/0003-4819-141-3-200408030-00001
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Published: Ann Intern Med. 2004;141(3):I-12.
The alveoli are the parts of the lung in which oxygen transfers from air to blood. When the amount of oxygen in air is reduced, changes occur in the lungs and heart to compensate for the low oxygen at the alveoli. These changes, which include constriction of the blood vessels in the lung, decrease a person's ability to exercise. High altitude is one situation where the amount of oxygen in air is low. The low oxygen and resulting changes in the heart and lungs account for many of the symptoms that people develop when they go from low to high altitudes. Sildenafil, a drug that has become a popular treatment for erectile dysfunction, causes the blood vessels of the lung to dilate (become wider). Previous studies have shown this effect of sildenafil in patients breathing air mixtures with low oxygen content at sea level. These observations have led experts to speculate that sildenafil might help prevent some of the problems with exercise ability caused by other conditions of low oxygen. One such condition is high altitude.
To explore the effects of sildenafil on exercise capacity in people exposed to low oxygen at high altitude.
14 healthy adults who were experienced mountain climbers.
The researchers assigned the study participants to receive sildenafil or a placebo pill in random order and measured their exercise capacity in 2 situations: 1) low altitude while breathing a mixture of air that contained only 10% oxygen and 2) high altitude at the Mount Everest base camp.
Sildenafil reduced high pressures in the lung's blood vessels at rest and with exercise and increased maximum exercise capacity in both settings.
The results of this small study are preliminary. Additional studies are needed to determine whether sildenafil would be helpful in acute mountain sickness.
Sildenafil might be useful in managing acute mountain sickness or other conditions caused by low oxygen levels at the alveoli.
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