¹Pfizer Central Research, Sandwich, UK

²National Spinal Injury Centre, Stoke Mandeville, UK

³Royal Victoria Hospital, Belfast, UK

⁴Regional Spinal Injury Centre, Southport, UK

^aAuthor for correspondence: Pfizer Central Research, Ramsgate Road, Sandwich CT13 9NJ, UK

Study design: This was a two-part pilot study in men with erectile dysfunction (ED) due to spinal cord injury (SCI: cord level range T6-L5). Part I was a randomised, double-blind, two-way cross-over study comparing a single dose of sildenafil 50 mg or placebo. Part II was a randomised, double-blind, parallel-group evaluation of sildenafil 50 mg or placebo, taken as required (not more than once daily) approximately 1 h prior to sexual activity, over a period of 28 days. Objectives: To assay the efficacy and safety of sildenafil 50 mg and placebo. Setting: Clinic- and home-based assessments in the United Kingdom. Methods: A total of 27 subjects who were able to achieve at least a grade 2 erection (hard, but not hard enough for penetration) in response to penile vibratory stimulation (PVS) were recruited. In Part I, the reflexogenic response of the penis to PVS was evaluated in the clinic while in Part II, the response to treatment was assessed in the home (global efficacy, questionniare, diary). Results: In Part I, 17/26 (65%) subjects had erections of >60% rigidity at the penile base (median duration 3.5 min) after sildenafil compared with 2/26 (8%) (median duration 0 min) after placebo (P=0.0003). In Part II, 9/12 (75%) subjects on sildenafil and 1/14 (7%) subjects on placebo reported that the treatment had improved their erections (P<0.005), and 8/12 (67%) and 2/13 (15%) men, respectively, indicated that they wished to continue treatment (P<0.02). An analysis of diary data showed no difference between the groups with respect to the mean number of erections hard enough for penetration (P=0.08). The mean proportion of attempts at sexual intercourse that were successful was 30 and 15%, respectively (P=0.21). Similarly, responses to the end-of-treatment questionnaire indicated that there were no significant differences between the groups with respect to the frequency of erections hard enough for sexual intercourse (P=0.47) or that lasted as long as the subject would have liked (P=0.11). No subject discontinued sildenafil due to adverse events. Conclusion: Sildenafil is an effective, well-tolerated oral treatment for ED in SCI subjects. Sponsorship: This study was funded by Pfizer Inc.

impotence; spinal cord injury; cyclic-GMP; phosphodiesterase inhibitors; sildenafil; erectile dysfunction; RigiScan