Pharmacokinetic activity of nitrites evaluated by digital pulse volume recording

Evaluation of the pharmacological properties of vasoactive drugs using routine pharmaco-chemical methods is often complex, time consuming and expensive. We used finger plethysmography for the evaluation of the bioactivity of two long-acting nitrite preparations. Eight healthy male volunteers were exposed to four different drugs: (1) Nitroglycerin; (2) Placebo; (3) Isosorbide dinitrate as Isotard Forte; (4) Isosorbide dinitrate as Cordil-40 SR. Digital pulse volume recording (PVR) was monitored for twelve hour periods. The shape of the PVR curve was used to calculate the diastolic amplitude response intensity, an indication of the vasoactive effect of the drug. There was no measurable response to the administration of placebo. The effect of nitroglycerin was maximal one hour after administration and disappeared after three hours. The long term effect of the two long-acting nitrite preparations was clearly demonstrated as compared to nitroglycerin. Noninvasive measurements of peripheral blood flow can serve as a convenient and accurate tool for pharmacokinetic studies of vasoactive drugs.