OBJECTIVES: Sildenafil (Viagra), an oral treatment for erectile dysfunction, has proved popular since its introduction in 1998. However, not all patients respond to this form of therapy. Consequently, this study investigated the efficacy of intracavernous alprostadil alfadex (EDEX/VIRIDAL) treatment in patients not responding to sildenafil. METHODS: In an open-label, multicenter study, patients with erectile dysfunction were treated with sildenafil for 4 weeks. The initial dose was 50 mg, which was increased to 100 mg if no response was achieved. Patients not responding to treatment, measured using the International Index of Erectile Function (IIEF) questionnaire, entered an alprostadil alfadex in-office titration phase, to determine the optimal dose, up to 40 microgram. A 6-week alprostadil alfadex at-home treatment phase followed. RESULTS: In 67 patients who did not respond satisfactorily to sildenafil, the alprostadil alfadex at-home therapy resulted in improvements in questions 3 and 4 of the IIEF in 60 (89.6%) and 57 (85.1%) patients, respectively. The mean improvement in IIEF score for these patients was 2.75 and 2.63 for questions 3 and 4, respectively. The most common side effect was penile pain in 25 (29. 4%) of 85 patients treated with alprostadil alfadex in-office and at home. CONCLUSIONS: Alprostadil alfadex therapy can be used effectively and safely in men who fail initial therapy with sildenafil.