PAPAVERINE TOPICAL GEL FOR TREATMENT OF ERECTILE DYSFUNCTION

Intracavernous injection of vasoactive substances has been shown to be an effective means of treatment of organic erectile dysfunction. Howe ver, up to 50% of men eventually discontinue treatment often because o f lack of spontaneity and needle phobia. This study was done as a phas e I, placebo controlled, nonblinded investigation of the safety and ef ficacy of a topical papaverine gel in the treatment of erectile dysfun ction. Of 20 men with organic impotence 17 completed the trial and 13 of these patients had spinal cord injuries. After application of a 15% and 20% papaverine base gel to the scrotum, perineum and penis, caver nous artery diameter was significantly increased (36%, p <0.001) as as sessed by color flow Doppler ultrasound. Peak systolic flow velocity i ncreased 26%. Only 3 of 14 patients achieved an increase in cavernous artery diameter of 75% or more and 2 of 14 had a peak systolic flow ve locity of 25 cm. per second or more after application of a topical bas e gel. Similar findings were present when only the patients with spina l cord injury were analyzed. The effect of a papaverine base in produc ing flow alterations to the penis is dose-dependent. A diminution in b lood pressure was present at 15 and 30 minutes after application to th e forearm, and the heart rate diminished from 68 to 62 beats per minut e after application to the genitalia. No patient was symptomatic. Seru m papaverine levels were not elevated over pre-application values. No hepatotoxic effects were demonstrated. Full clinical erections (mean d uration 38.7 minutes) were present in 3 patients but were also present with the placebo preparation (mean duration 8.0 minutes). In conclusi on, topical papaverine gel appears to be safe and well tolerated after application to the genitalia, and increases blood flow to the penis w ith a 15% and 20% base preparation. Minimal systemic absorption occurs and, thus, effects are probably from local absorption. Topical therap y appears to augment reflex erections in the spinal cord injury patien t and may be especially beneficial in this population. Further investi gation is warranted at higher concentrations or in combination with di fferent skin absorption enhancers.