Risk Factors for an Early Increase in Dose of Vasoactive Agents for Intracavernous Pharmacotherapy

Aims: This study was to identify factors that influence the early increase in the dose of intracavernous vasoactive agents to maintain erection for satisfactory intercourse and to elucidate when the dose increase would begin. Methods: Seventy-nine patients using intracavernous pharmacotherapy with tri-mix (PGE1, papaverine, and phentolamine) over a 3- to 4-year period were enrolled. At 3-month intervals, patients were questioned about changes in dose to maintain erection for satisfactory intercourse and frequency of injection, and underwent examination of the penis. The patients were divided into 2 groups: group A, dose increase of ≧20% after initiating home therapy, and group B, no change or an increase in dose Results: A significant increase (p < 0.01) in dose was started 2–3 years after initiating pharmacotherapy. The initial doses of group A at 2–3 and 3–4 years were significantly higher than those of group B (p < 0.01). There were no significant differences in the age of the patients, duration of erectile dysfunction, incidence of accompanying vascular risk factors, frequency of injection, or incidence of fibrous plaques between group A and group B, both at 2–3 and 3–4 years. Conclusion: The initial dose of intracavernous vasoactive agents (tri-mix) may be a unique risk factor for the early increase in dose to maintain erection for satisfactory intercourse.