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OBJECTIVE To provide an update on the efficacy and safety of tadalafil, a phosphodiesterase‐5 inhibitor, in the treatment of erectile dysfunction (ED). PATIENTS AND METHODS In all, 2102 men (mean age 56 years) with mild‐to‐severe ED of various causes were randomized to placebo or tadalafil, taken as needed with no food restrictions, at fixed ‘on‐demand’ doses of 10 or 20 mg in 11 randomized, double‐blind, placebo‐controlled trials lasting 12 weeks. The three co‐primary outcomes were changes from baseline in the erectile function domain of the International Index of Erectile Function (IIEF) and the proportion of ‘yes’ responses to questions 2 and 3 of the Sexual Encounter Profile (SEP). Additional efficacy instruments included a Global Assessment Question (GAQ). RESULTS Compared with placebo, tadalafil gave significantly better outcomes. Patients receiving either dose of tadalafil had a significant mean improvement of 6.5 and 8.6, respectively, in the IIEF erectile function domain score from baseline (P < 0.001 vs placebo). At both doses the mean success rate for intercourse attempts (SEP‐Q3) was 58% and 68%, respectively, compared with 31% in the placebo group (P < 0.001), and 71% and 84% reported improved erections at the endpoint (GAQ), vs 33% on placebo (P < 0.001). Tadalafil was effective up to 36 h after dosing and was effective regardless of disease severity and causes, and in patients of all ages. The most frequent adverse events were headache, dyspepsia, back pain and myalgia. CONCLUSION Tadalafil was an effective and well‐tolerated treatment for ED.

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Oral sildenafil is an effective and well-tolerated treatment for erectile dysfunction in men with diabetes.

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It was recently reported in the rat that vardenafil given in a continuous long-term manner was successful in preventing smooth muscle fibrosis in the penile corpora cavernosa and corporal venoocclusive dysfunction (CVOD) that occur following bilateral cavernosal nerve resection (BCNR), a model for human erectile dysfunction after radical prostatectomy. To expand on this finding and to determine whether this effect was common to other PDE5 inhibitors, and occurred in part by stimulation of the spontaneous induction of inducible nitric oxide synthase (iNOS, also known as NOS2), male Fischer 344 rats (N ¼ 10/group) were subjected to either BCNR or unilateral cavernosal nerve resection (UCNR) and treated with sildenafil (20 mg kg À1 day À1 ) in the drinking water daily for 45 days. Additional BCNR groups received L-NIL (6.7 mg kg À1 day À1 ) as inhibitor of iNOS activity, with or without concurrent sildenafil administration. It was determined that sildenafil, like vardenafil, (1) prevented the 30% decrease in the smooth muscle cell/collagen ratio, and the 3-4-fold increase in apoptosis and reduction in cell proliferation, and partially counteracted the increase in collagen, seen with both UCNR and BCNR; and (2) normalized the CVOD, measured by dynamic infusion cavernosometry, induced by both BCNR and UCNR. The long-term inhibition of iNOS activity exacerbated corporal fibrosis and CVOD in the BCNR rats, but sildenafil functional effects were not affected by L-NIL. These data suggest that the salutary effects of continuous long-term PDE5 inhibitors on erectile function post-cavernosal nerve resection involve their ability to prevent the alterations in corporal histology induced by cavernosal nerve damage, in a process apparently independent from endogenous iNOS induction.

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