Effect of locally applied trapidil on norepinephrine- and dinoprost-evoked hand vein constriction in healthy men.

In this study the effect of locally administered trapidil on human hand veins was examined. 10 healthy male volunteers aged 20 - 30 years were included. The dorsal hand vein compliance technique was used. In a crossover design the influence of locally infused trapidil (mainly 5 - 400 microg/min) on hand veins preconstricted with either norepinephrine (adrenoceptor agonist) or dinoprost (prostaglandin F2alpha) was investigated. Preconstriction reduced the vein diameter by about 80% with continuous local infusion of individually determined doses of norepinephrine in the range 11 - 1,000 ng/min and dinoprost in the range 90 - 5,600 ng/min. Blood pressure, cardiac function (electrocardiogram) and skin temperature of the hand infused were monitored. Locally applied trapidil produced a dose-dependent dilation of hand veins preconstricted with norepinephrine and dinoprost. The corresponding ED50 values of trapidil did not differ significantly on an intraindividual comparison. Clinically important side effects with the drugs used were not observed. The results indicate that trapidil has a direct dilating action on superficial veins in humans. This effect is apparently achieved without involvement of adrenoceptors or prostanoid receptors in venous smooth muscle.