Axial penile rigidity as primary efficacy outcome during multi-institutional in-office dose titration clinical trials with alprostadil alfadex in patients with erectile dysfunction

The purpose of the study was to utilize axial penile buckling testing as a primary efficacy variable of erection quality during multi-institutional in-office dose titration testing with alprostadil alfadex, prostaglandin E-1, (PGE(1))-alpha-cyclodextrin, (EDEX(R)/VIRIDAL(R), Schwarz Pharma) in patients with erectile dysfunction. In 41 study sites, in three different dose titration studies involving 894 patients with impotence >6 months, a buckling test was performed and repeated every 10 min for up to 60 min, within 30 min following alprostadil alfadex administration, or when two consecutive circumference measurements reached maximum values. The buckling device consisted of a standard weight scale attached to a 2 inch diameter plastic cap with a concavity on its ventral surface (H. Eric Richards, Inc., Canton MA). A positive test was associated with absent penile shaft buckling to a downward force of 1.0 kg, slowly applied to the glans in the axis of the erect shah. A total of 630 (71%) patients experienced at least one positive buckling test. Three consecutive positive buckling tests, implying a functionally rigid erection for at least 20 min, were noted in 521 (58%) patients. There were high correlations between the presence of three consecutive positive buckling tests following alprostadil alfadex injection and the patient's (83% of cases) and the investigator's (88% of cases) evaluation of adequacy of erection for intercourse. Similarly, there were high correlations between the presence of negative buckling tests and the patient's (95% of cases) and the investigator's (96% of cases) evaluation of inadequacy of erection for intercourse. The axial penile buckling test offers a simple, reliable, and inexpensive method to objectively quantify erectile response following in-office dose titration of intracavernosal alprostadil alfadex. The high correlation to subjective patient/investigator assessment adds to the validity of the test.