Objective: To compare two injectable treatments, alprostadil 5-20 microg powder for injection and a combination of vasoactive intestinal polypeptide (VIP) and phentolamine in patients with erectile dysfunction (ED).
Design and methods: This was an open multicentre, randomised crossover study comprising two phases. The first phase established the dose of each drug required to produce an erection suitable for sexual intercourse (grade 3 erection). In phase 2, responders to both drugs received, in random order, four doses of VIP/phentolamine, presented as ampoules, and four doses of alprostadil, presented as powder for injection. This was followed by four doses of VIP/phentolamine, presented in an autoinjector. In both phases, patient preference was assessed for each preparation.
Results: 187 patients were recruited. In the first phase, both treatments were effective, (83% alprostadil vs. 73% VIP/phentolamine, p = 0.002) but more patients preferred VIP/phentolamine (69 vs. 31%, p = 0.011). In phase 2 (n = 107), the proportion of injections that produced a grade 3 erection was similar for all three treatments (83-85%), but both presentations of VIP/phentolamine (ampoule and auto-injector) were preferred by significantly more patients (p < 0.001). Compared with both presentations of VIP/phentolamine, alprostadil produced a higher frequency of pain (28% of injections vs. 3% for each VIP/phentolamine presentation; p < 0.001) and a lower frequency of facial flushing (3 vs. 16-17%; p < 0.001).
Conclusions: VIP/phentolamine and alprostadil were effective treatments for ED, however the VIP/phentolamine combination was preferred by more patients, which may be because it was much less likely to cause pain.