Long-term efficacy of sildenafil and tachyphylaxis effect
Abstract
PURPOSE: We observed that patients who initially responded to sildenafil frequently became resistant to it with time. We evaluated the long-term efficacy of sildenafil. MATERIALS AND METHODS: A telephone survey was conducted of patients during the first year of sildenafil usage, and another one was completed 2 years later of the same group. RESULTS: During the first survey, the etiology of impotence included post radical prostatectomy in 25, arterial insufficiency in 26, diabetes in 19, neurogenic impotence in 12, suspected venous leak in 9, proved venous leak in 7, Peyronie's disease in 6 and unspecified in 47 patients. The overall improvement rate, which was defined as the ability to initiate and maintain erections for successful intercourse, was 74%. The dose necessary to achieve this response was 100 mg. sildenafil in 15% of patients, 50 mg. in 83% and 25 mg. in 2%. During the second survey, information was collected on 82 patients and only 43 (52%) had continued treatment. Of the 69 patients who reported an initial good response 41 (59%) were still using sildenafil, and of the 43 who were still using it 16 (37%) had to increase the dose by 50 mg. to achieve an adequate result. There was no significant relationship between the need to increase the dose and frequency of treatment per month. Reduction in efficacy ranged from 15% to 50% (mean 36 +/- 12%) and the time to loss of efficacy ranged from 1 to 18 months (mean 11 +/- 5). Of the 82 patients in the second surgery, 39…
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