Objective double-blind evaluation of erectile function with intracorporeal papaverine in combination with phentolamine and/or prostaglandin E1

We performed a double-blind, crossover study using objective measurements to compare maximum rigidity and duration of erections with papaverine hydrochloride in combination with phentolamine mesylate and/or prostaglandin E1. The rationale for the protocol was to combine a smooth muscle relaxant (papaverine) with either or both vasodilating agents (phentolamine and prostaglandin E1) commonly used for injection therapy. The 7 volunteer patients with organic impotence documented by abnormal nocturnal penile tumescence testing were injected with 0.5 to 1.0 ml. papaverine (30 mg./ml.) in combination with phentolamine (0.5 mg./ml.) and/or prostaglandin E1 (5 μg./ml.). Each patient received 2 injections on each of 2 testing dates; injection 2 was given after tumescence resulting from injection 1 had subsided completely. The medications were given in a randomized, counterbalanced order following double-blind procedures. Patients evaluated the erections subjectively. In addition, the RigiScan device was used to measure maximum rigidity and duration of erections. All patients observed increased duration of erections with both combinations containing prostaglandin E1. Analysis of RigiScan measurements showed no statistically significant differences for maximum rigidity (p >0.1) but significantly greater duration of erections with papaverine plus prostaglandin E1, and papaverine plus phentolamine plus prostaglandin E1 compared to papaverine plus phentolamine (p <0.001). There was no statistical difference in rigidity or duration of erections between papaverine plus prostaglandin E1 and papaverine plus phentolamine plus prostaglandin E1. No patient reported significant penile pain with any of the injections. We conclude that the combination of papaverine and prostaglandin E1 produces erections of longer duration than papaverine plus phentolamine and that no additional benefit is gained by adding phentolamine to a combination of papaverine and prostaglandin E1. Further studies are in progress to define optimal dose response curves for papaverine and prostaglandin E1 as individual agents and in combination.