[The meanings of the papaverine test]

Intracavernous administration of papaverine is now commonly employed for diagnosis and therapy of impotence. To assess the pharmacokinetics of papaverine, we recorded its concentration in peripheral blood and also in cavernous blood after intravenous and intracavernous injection of 40 mg of papaverine. Peripheral blood was sampled serially after injection. Plasma was immediately extracted and then kept at at -40 degrees C until analysis. High pressure liquid chromatography was used to record the concentration of papaverine. The maximum serum concentration of papaverine measured after intracavernous injection was 7.7 ng/ml, which was considerably lower than the average serum concentration of 24.0 ng/ml after intravenous injection. Peak serum concentration was reached 1 min after intravenous injection and 10 min after intracavernous injection. It is clear that the corpus cavernosum constitutes a separate pharmacokinetic compartment. Therefore there was no significant difference between the papaverine concentration in peripheral blood of patients who showed full erection after intracavernous injection and that of patients who did not achieve erection. The concentration of papaverine in the intracavernous blood of a fully erected penis was only about 1 microgram/ml after 20 min. This concentration is similar to that in cavernous blood of those who showed excessively persistent erection. Our results imply that papaverine administered into the cavernous space relaxes smooth muscle, and is then washed out to general circulation, and the concentration in the cavernous space reaches a low level of about 1 microgram/ml. The low concentration level is maintained for several hours during erection. Therefore, we presume that papaverine acts on both the inflow system and smooth muscle of cavernous tissue in the phase of producing erections.(ABSTRACT TRUNCATED AT 250 WORDS)