Effects of pentoxifylline and alprostadil on ocular hemodynamics in healthy humans

PURPOSE. Alprostadil, a prostaglandin (PG)E₁ analogue and pentoxifylline, an alkylxanthine derivate, have been shown to exert vasodilatory effects in several vascular beds. The purpose of the present study was to investigate the effect of PGE₁ and pentoxifylline on the ocular circulation. METHODS. A placebo-controlled, double-masked, three-way, crossover study was performed in 15 healthy male subjects. Subjects received pentoxifylline (300 mg), PGE₁ (alprostadil 60 μg), or placebo intravenously over 2 hours on three trial days. Choroidal red blood cell flow was assessed with laser Doppler flowmetry and pulsatile choroidal blood flow with laser interferometric measurement of fundus pulsation amplitude (FPA). Retinal blood cell flow was calculated based on the measurements of maximum erythrocyte velocity in a retinal vein assessed with bidirectional laser Doppler velocimetry, and diameter measurements of retinal vessels were obtained with a retinal vessel analyzer. RESULTS. Pentoxifylline increased FPA by 15.4% ± 1.1% (P < 0.001 versus placebo and baseline). Alprostadil tended to increase FPA, but this effect did not reach the level of significance (P = 0.07 versus placebo). Choroidal blood flow as measured with laser Doppler flowmetry tended to increase during pentoxifylline and PGE₁ infusion by 8.9% ± 2.9% (P = 0.062) and 4.5% ± 6.2% (P = 0.29), respectively, but none of these effects was significant. The drugs under study had no effect on mean red blood cell velocity in retinal veins, on retinal vessel diameters, intraocular pressure, blood pressure, or pulse rate. CONCLUSIONS. PGE₁ did not alter the parameters of retinal or choroidal circulation in healthy subjects. Pentoxifylline increased FPA, but did not change choroidal blood flow as measured with laser Doppler flowmetry and did not affect retinal blood flow parameters. Accordingly, neither pentoxifylline nor PGE₁ appears to be suitable to improve ocular blood flow in healthy subjects. Whether long-term treatment with alprostadil would improve choroidal blood flow in patients with vascular disease remains to be established.