Randomized crossover trial of amoxapine versus vitamin B(12) for retrograde ejaculation

OBJECTIVE: To compare the efficacy and safety of amoxapine and vitamin B(12) for treating retrograde ejaculation (RE). MATERIALS AND METHODS: Between May 2009 and November 2012, this open-label, randomized, crossover study enrolled 26 men suffering with RE at Department of Reproductive Medicine, Omori Hospital. Patients were randomly allocated into two groups (n=13 each). The amoxapine-B(12) group received amoxapine (50 mg daily for 4 weeks, orally) followed (after a 1-week washout period) by vitamin B(12) (500 μg three-times daily for 4 weeks). The B(12)-amoxapine group received the opposite regimen. All patients masturbated to ejaculation at least twice during each treatment period. The primary outcome was antegrade ejaculation of semen, as reported by the patient, on more than one occasion during either treatment period (defined as treatment success). Any adverse events were noted. Success rates were compared between treatments using Fisher’s exact test. RESULTS: One patient (B(12)-amoxapine group) withdrew for personal reasons (breakdown of marital relations); all other patients completed the study. Overall success rate was 88% (22/25). Success rate was higher for amoxapine than for vitamin B(12) (80%, 20/25 vs 16%, 4/25; P<0.0001). 18 patients were responsive to amoxapine but not to vitamin B(12), 2 patients were responsive to vitamin B(12) but not amoxapine, 2 patients were responsive to both drugs, and 3 patients had no response to either drug. One patient (4%) reported sleepiness and 2 (8%) reported constipation while receiving amoxapine. No adverse events were reported during vitamin B(12) treatment. CONCLUSIONS: Amoxapine may be an effective, safe and well-tolerated therapy for RE.