Influence of the method of intracavernous injection on penile rigidity: A possible pharmacokinetic explanation

Abstract

Objectives To study whether the method of intracavernous injection of vasodilators has an effect on the clinical outcome and to explain the mechanism of possible influence. Methods In an open clinical study, penile rigidity after bolus injection was compared with rigidity after slow injection in 52 self-injecting, impotent patients. In 35 volunteers, venous plasma levels of intracavernosally injected drugs were followed under different injection conditions: slow injection of undiluted drug, slow injection of diluted drug, bolus injection, use of a tourniquet, or slow injection followed by squeeze of the corpora. Results Of the 52 patients, 28 reported better penile rigidity after a bolus injection than after slow injection of vasodilators. The other 24 reported no difference in rigidity. Systemic side effects did not occur, but 4 patients reported local pain after bolus injection. In the 35 volunteers, the lowest plasma levels were observed when a tourniquet was used or when a bolus injection was performed; the quickest transfer was observed after a slow injection of a low volume of the drug. Conclusions Better rigidity was observed after bolus injection in a majority of the patients using the same dose of vasodilators. This could be due to the pharmacokinetic phenomenon of a slower drug transfer to the systemic circulatory system after a bolus than after a slow injection.