Clinical safety profile of sildenafil in Singaporean men with erectile dysfunction: pre-marketing experience (ASSESS-I evaluation)

Sildenafil: two decades of benefits or risks?

Sildenafil is a selective inhibitor of cyclic guanosine monophosphate (cGMP)-specific phosphodiesterase type 5 (PDE-5). A patent was registered for this drug in 1990, which expired in 2010. Since expiration, the drug has been marketed under various trade names or as generic drugs. Numerous clinical trials have been conducted addressing the effectiveness of the drug for erectile dysfunction (ED) and its safety regarding the presence or absence of specific comorbidities. After over 20 years in the market, we need to ask: has the scientific community reached a general consensus as to the overall efficacy and safety of the drug? Can we firmly state that the benefits of the drug outweigh its risks? This review suggests that sildenafil is an effective and easily manageable treatment for erectile dysfunction, both in the absence and in the presence of comorbidities. After two decades of the emergence of sildenafil as a drug of choice for the treatment of ED (and the numerous studies and clinical trials undertaken during this time span), it is now possible to state that the benefits of the drug do outweigh the risks, and represent an significant improvement in the quality of life in men with ED.

The possible role of the NO-cGMP pathway in nociception: different spinal and supraspinal action of enzyme blockers on rat dorsal horn neurones

In the literature, the pro- or antinociceptive effects of nitric oxide (NO) and cyclic guanosine monophosphate (cGMP) are discussed controversially. Our laboratory and others have reported that in the spinal cord a local lack of NO has an excitatory action on the ongoing (background) activity of dorsal horn neurones. Here, we tested the hypothesis that this effect of NO is mediated by cGMP and that part of the controversy is due to differences in the spinal and supraspinal actions of both compounds. In anaesthetised rats, impulse activity of lumbar dorsal horn neurones was recorded, and blockers of NO- and cGMP-synthesis, as well as the phosphodiesterase 5 (PDE5) inhibitor sildenafil (which increases the cGMP level), or 8-Bromo-cGMP (a membrane permeable cGMP analogue) were administered spinally or supraspinally. Topical superfusion of the spinal cord with a blocker of the guanylyl cyclase (ODQ) to reduce the cGMP level led to an increase in background activity of nociceptive lumbar dorsal horn neurones similar to that caused by l-NAME, a blocker of the NO synthase. Spinal superfusion with sildenafil or 8-Bromo-cGMP had no excitatory effect. In contrast, injections of sildenafil or 8-Bromo-cGMP into the third cerebral ventricle caused an increased background activity in lumbar dorsal horn neurones, while l-NAME and ODQ were ineffective. The results show that at the spinal level, a lack of cGMP and NO has an excitatory action on dorsal horn neurones, whereas supraspinally an elevated level of cGMP is excitatory.

Sildenafil Citrate Treatment for Erectile Dysfunction After Kidney Transplantation

OBJECTIVE

Our goal was to analyze the morbidity of organic erectile dysfunction (ED) in kidney-transplant patients and to evaluate the efficacy and reliability of sildenafil citrate treatment.

METHOD

Sixty-five ED patients with normal graft function for 3 to 12 months after kidney transplantation were involved in our study. Erectile dysfunction was diagnosed in all the patients by the International Index of Erectile Dysfunction (IIEF). Among them, 10 patients were in light degree; 32 patients in moderate degree, and 23 patients in severe degree according to IIEF score. All of the patients underwent medical history, physical and chemical examinations. In each patient, the IIEF score, blood urea nitrogen, creatinine, and trough concentrations of cyclosporine were compared before and after taking sildenafil citrate at an initial dose of 50 mg every night.

RESULTS

Twenty-six patients without ED before transplantation suffered ED after the operation, and 32 patients with ED before transplantation noticed worsening. Taking sildenafil citrate was effective in 53 patients (81.54%). There were no statistical differences in blood urea nitrogen, creatinine, or trough concentrations of cyclosporine in patients before and after sildenafil treatment.

CONCLUSIONS

The morbidity of organic erectile dysfunction increased after transplantation. Sildenafil citrate treatment for ED in kidney-transplant patients was effective and safe. Graft function and trough concentrations of cyclosporine were not affected by sildenafil citrate.

Safety and efficacy of vardenafil in patients with erectile dysfunction: Result of a bridging study in Japan

AIM

Vardenafil is a selective and highly potent phosphodiesterase type 5 (PDE5) inhibitor for the treatment of erectile dysfunction (ED), with improved selectivity for PDE5 and demonstrated efficacy for improving sexual function in men with ED. The current study investigated the safety and efficacy of this new PDE5 inhibitor in Japanese men with ED.

METHODS

This was a prospective, double blind, randomized clinical trial designed to evaluate the efficacy and safety of vardenafil. Following a 4-week treatment-free observation period, 283 eligible patients were randomized to 12 weeks treatment with vardenafil 5 mg, 10 mg, 20 mg, or placebo. Primary efficacy responses were assessed using the scores of Q3 and Q4 of the international index of erectile function (IIEF).

RESULTS

All three vardenafil doses showed significantly better improvement than the placebo group in Q3 and Q4 scores of the IIEF questionnaire, either at 12 weeks or at the 'last observation carried forward' (LOCF, P < 0.0001). Q3 scores were improved to 4.06 with vardenafil 5 mg, 4.53 with vardenafil 10 mg, and 4.64 with vardenafil 20 mg, versus 3.17 with placebo. Comparable scores for Q4 were 3.47, 4.15 and 4.31 versus 2.31 for placebo. Up to 86% of patients achieved improved erections as assessed by the global assessment question (GAQ). Reported adverse event rates were 35.3%, 45.3% and 54.5% with vardenafil 5 mg, 10 mg and 20 mg, respectively, versus 21.1% in the placebo group. No serious adverse drug reactions were reported. The most common treatment-emergent adverse events were transient headache, flushing and rhinitis, which were mostly mild.

CONCLUSION

Vardenafil is an effective and well-tolerated treatment for ED and provides improvement in key indices of erectile function among Japanese men with ED. The results of our trial show that up to nearly 90% of patients achieve improved erections with the administration of vardenafil.