The pH analysis of papaverine-phentolamine and prostaglandin E1 for pharmacologic erection

Although papaverine-phentolamine preparations are being employed for pharmacologic erection programs across the nation, their chemical properties have not been described in the literature. We found that the pH of papaverine-phentolamine solution in all concentrations tested remained less than 4.0. Attempts to buffer the solution resulted in a precipitate at a pH greater than or equal to 5.0. The pH of prostaglandin E1 was less than 5.0 but could be easily buffered to pH 7.4 or even 10.75 and remained stable. The effect of an acidic solution on corporal connective tissue and smooth muscle meshwork is unknown. We believe that buffering by blood will lead to the precipitation of papaverine-phentolamine and may cause primary intracorporal scarring. Extravasation or improper injection into the subcutaneous tissue exposes the mixture to blood and may secondarily result in additional scarring for the same reason. Therefore, prostaglandin E1 may be a more appropriate agent for penile injection.