Abstract Purpose Prostaglandin E1 sterile powder and sterile solution are 2 new formulations of exogenous prostaglandin E1 that are more convenient for auto-injection therapy for erectile dysfunction than the presently used pediatric sterile solution. Therefore, the pharmacodynamic profiles of intracavernous prostaglandin E1 sterile powder and nonalcohol sterile solution were compared with the pediatric sterile solution in men with erectile dysfunction who were known to be stable responders to intracavernous prostaglandin E1. Materials and Methods Based on the dose used at home, patients were randomized to 1 of 5 dose groups: 0 microgram (placebo), 2.5 microgram, 5 microgram, 10 microgram or 20 microgram. Each patient received a single injection of the same dose of each of the 3 formulations. The primary pharmacodynamic end points were clinical evaluation of erectile response, RigiScan † † Dacomed, Minneapolis, Minnesota. real-time evaluation of erectile response and patient evaluation of erectile response. Results No significant differences were identified among the formulations for any of these end points, either by comparison among all active doses or by comparison at each prostaglandin E1 dose level. There was also little or no intra-patient variation in dose response and the inter-dose variation in response between patients was not significant. Pharmacodynamic end points were well intercorrelated, although assessment of erectile response by the patients tended to be more positive than that by RigiScan or clinical evaluation. There were no major side effects. Penile pain on injection and/or during erection occurred in 9 to 17 percent of the patients according to the formulations. However, penile pain was also reported by 11 percent of the placebo-treated patients. Conclusions The 3 formulations of prostaglandin E1 showed equivalence and were safe for the treatment of erectile dysfunction with respect to side effects.