Influence of systemically given placebo, trapidil and isosorbide dinitrate on norepinephrine-evoked hand vein constriction in healthy subjects.

Since trapidil (CAS 15421-84-8) is able to dilate human hand veins after local intravenous administration, four studies were carried out in healthy male volunteers using the dorsal hand vein compliance technique to test the influence of common systemic single doses of trapidil (200 mg orally, 100 mg intravenously) and isosorbide dinitrate (CAS 87-33-2, 20 mg orally) on norepinephrine (CAS 51-41-2)-evoked hand vein constriction in comparison with oral placebo. Oral placebo and oral trapidil were studied in a randomized double-blind cross-over design in 10 subjects aged 20 to 30 years, and oral isosorbide dinitrate and intravenous trapidil, in a randomized open cross-over design in 8 subjects aged 22 to 29 years. In the three similar studies with oral medications dose-response curves for venoconstriction by locally infused norepinephrine were established before and 1 h, 2 h and 3 h after oral medication and ED50 values of norepinephrine were calculated.