Long-term efficacy of sildenafil and tachyphylaxis effect

Purpose: We observed that patients who initially responded to sildenafil fr equently became resistant to it with time. We evaluated the long-term effic acy 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 l ater of the same group. Results: During the first survey, the etiology of impotence included post r adical prostatectomy in 25, arterial insufficiency in 26, diabetes in 19, n eurogenic impotence in 12, suspected venous leak in 9, proved venous leak i n 7, Peyronie's disease in 6 and unspecified in 47 patients. The overall im provement rate, which was defined as the ability to initiate and maintain e rections 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 pa tients and only 43 (52%) had continued treatment. Of the 69 patients who re ported an initial good response 41 (59%) were still using sildenafil, and o f 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 betw een the need to increase the dose and frequency of treatment per month. Red uction 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 pat ients in the second surgery, 39 (48%) stopped using sildenafil. A total of 28 (74%) patients reported a good initial response on the first survey, and 6 had spontaneous erections and no longer needed treatment. However, 14 (5 0%) patients discontinued sildenafil because of the loss of efficacy. In th is group 10 patients had side effects, mainly headache and flushing of the face and nose, and only 2 discontinued treatment because of them. Conclusions: Our data suggest that there is a possible tachyphylaxis effect with sildenafil. Of the patients who were followed for 2 years 20% had to increase the sildenafil dose to have the same effect and 17% discontinued u se due to loss of efficacy.