A prospective randomized study to optimize the dosage of trimix ingredients and compare its efficacy and safety with prostaglandin E1.

Intracavernous injection of Trimix (Tx) is indicated for patients unsuitable for prostaglandin E1 (PgE1) injection due to lack of response, pain or cost. We believe that the ideal ratio of ingredient doses in Tx is yet to be found. We postulated that increasing the doses of individual drug components in an orderly manner would convey important data on penile hemodynamic response. Such information is needed to choose an effective and less costly alternative to PgE1 with least side effects. We set out to evaluate the impact of varying the ingredient dosage on response and short-term safety of Tx compared with PgE1. We prospectively randomized 180 consecutive patients with erectile dysfunction into nine equal groups and each group received a different dose of Tx, namely phentolamine (1 mg) plus one dose of PgE1 (2.5, 5 or 10 microg) and one dose of papaverine (5, 10 or 20 mg). Each patient was injected with 20 microg PgE1 and one dose of Tx in two clinic visits 1 week apart. Following injection, duplex ultrasound of cavernous arteries and axial rigidometry were carried out. Patients ranked the quality of erection, estimated overall satisfaction and reported time to detumescence and side effects. Patients' mean age was 50.5+/-11.7 y with underlying organic condition in 91.1%. There were no significant differences between PgE1 and Tx with regard to peak cavernous artery flow, time to erection, patients' satisfaction, average axial rigidity and pain. PgE1 produced higher end diastolic velocity, shorter duration of erection and less priapism. Patients did not show a preference for either drug or any particular dosage. We conclude that even at the smallest dose of ingredients of Tx, there are no significant differences in hemodynamic effects, rigidity, pain and self-satisfaction between the two drugs. However, Tx produces a longer duration of erection and more priapism than PgE1.