Effectiveness of oral L-arginine in first-line treatment of erectile dysfunction in a controlled crossover study

Background and Aims: Relaxation of cavernous smooth muscle is a parasympath etic and non-adrenergic, noncholinergic mediated process which requires nit ric oxide (NO). NO is synthesized from L-arginine by NO synthase (NOS). Som e studies report good clinical results under oral L-arginine medication in the treatment of erectile dysfunction. We examined the effectiveness and sa fety of L-arginine in the treatment of mixed-type impotence. Methods: 32 pa tients (mean age 51.6 years) with mixed-type impotence diagnosed according to the results of sexual history and urological examination were enrolled i n a randomized, placebo-controlled, crossover comparison of an oral placebo with 3 x 500 mg L-arginine/day. A validated questionnaire (KEED) was used to define the grade of impotence with a score. The treatment consisted of t wo 17-day courses (50 tablets). After a 7-day washout period the patients w ho initially received the placebo for 17 days were switched to L-arginine a nd vice versa. We assessed the efficacy with the validated questionnaire at the end of each drug period. Results: 30 patients (94%) completed the whol e treatment schedule. Five (17%) patients reported a significant improvemen t in erectile function at the end of the L-arginine phase and 6 (20%) patie nts after the placebo period, 17 (56%) patients showed little improvement w ith L-arginine and 13 (43%) with placebo. In 8 patients (27%) of the verum group there was either no change in the ED score or even a slight worsening . No statistical difference in the impotence scores were found. No drug-rel ated adverse effects occurred with L-arginine treatment. Conclusion: Oral L -arginine 3 x 500 mg/day is not better than placebo as a first-line treatme nt for mixed-type impotence. Copyright (C) 2000 S. Karger AG, Basel.