Rheological, cardiorespiratory and cerebrovascular effects of pentoxifylline following acclimatization to 3800 meters.

Pentoxifylline is a non-selective phosphodiesterase inhibitor used for the treatment of peripheral artery disease. Pentoxifylline acts through cyclic adenosine monophosphate, thereby enhancing red blood cell deformability, causing vasodilation and decreasing inflammation, and potentially stimulating ventilation. We conducted a double-blind, placebo-controlled, crossover, counterbalanced study to test the hypothesis that pentoxifylline could lower blood viscosity, enhance cerebral blood flow and decrease pulmonary artery pressure in lowlanders following 11-14 days at 3800m. Participants (6M/10F; age=27±4 years) received either a placebo or 400 mg of pentoxifylline orally the night before and again two-hours before testing. We assessed arterial blood gases, venous hemorheology (blood viscosity, red blood cell deformability and aggregation) and inflammation (TNF-α) in room-air (end-tidal oxygen partial pressure ~52 mmHg). Global cerebral blood flow (gCBF), ventilation and pulmonary artery systolic pressure (PASP) were measured in room air and again after 8-10 minutes of isocapnic hypoxia (end-tidal oxygen partial pressure: 40 mmHg). Pentoxifylline did not alter arterial blood gases, TNF-α, or hemorheology compared to placebo. Pentoxifylline did not affect gCBF or ventilation during room-air or isocapnic hypoxia compared to placebo. However, in females, PASP was reduced with pentoxifylline during room air (placebo=19±3 and pentoxifylline=16±3 mmHg; p=0.021) and isocapnic hypoxia (placebo=22±5 and pentoxifylline=20±4 mmHg; p=0.029), but not in males. Acute pentoxifylline administration in lowlanders at 3800m had no impact on arterial blood gases, hemorheology, inflammation, gCBF, or ventilation. Unexpectedly, however, pentoxifylline reduced PASP in female participants, indicating a potential effect of sex on the pulmonary vascular responses to pentoxifylline.