Difference in nitroglycerin dose-response in the venous and arterial beds.

In twelve healthy volunteers given nitroglycerin sublingually (1.6 mg) or epicutaneously (12 mg), venous distensibility was found to be maximal, even at low plasma concentrations (less than 0.2 ng/ml); there was no further change with increasing concentrations. Peripheral arterial resistance, on the other hand, decreased progressively with rising plasma concentrations and no distinct plateau was demonstrable, even at the highest plasma concentration measured (greater than 2.0 ng/ml).