Background: Sildenafil citrate was introduced as a treatment for erectile dysfunction in April 1998 in the United States and has been available since March 1999 in Japan. In this article, we assess the efficacy of sildenafil in the treatment of erectile dysfunction in Japanese men after radical retropubic prostatectomy for localized prostate cancer.
Methods: Of 106 men who underwent radical retropubic prostatectomy between January 1994 and March 2000, 43 were prescribed sildenafil at their request after radical retropubic prostatectomy. Medication was initiated at 25 mg, and if this was ineffective, the dose was increased to 50 mg. Of the patients, 18 underwent bilateral and 21 unilateral nerve sparing (NS) procedures, while in 4 patients, a non-NS procedure was performed. These patients were interviewed using a questionnaire about their response to sildenafil and using the 5-item International Index of Erectile Function (IIEF-5) questionnaire.
Results: Thirty-three of the 43 patients were eligible for evaluation of the efficacy of sildenafil and 27 completed the IIEF-5 questionnaires. Sildenafil at 50 mg had a better effect on sexual function than 25 mg in most Japanese patients. Of the 16 patients who underwent bilateral NS procedures, 10 (62.5%) had improved ability for intercourse and 3 (18.8%) had improved erections. Of the 13 patients who underwent unilateral NS procedures, 7 (53.8%) had improved ability for intercourse and 4 (30.8%) had improved erections. None of the 4 patients who underwent non-NS procedures had a positive response. Of 24 patients with positive response to sildenafil, 3 (12.5%) did not have to take sildenafil after receiving it because they did not require it for intercourse. Mean IIEF-5 score increased from 4.3 to 11.4 (P < 0.0001). Patient age, time since surgery, PSA and pathological stage did not have statistically significant effects on outcome. The most commonly cited adverse effect was headache (21%).
Conclusion: Sildenafil is equally effective for erectile dysfunction in Japanese patients who have undergone bilateral and unilateral NS procedures, and aids recovery of natural erectile function after radical retropubic prostatectomy. However, non-NS procedure patients had no response to sildenafil. This study suggested that sildenafil is well tolerated and should be initially used for treatment of Japanese men with erectile dysfunction after radical retropubic prostatectomy.