Tolerability and safety profile of sildenafil citrate (Viagra) in Latin American patient populations

Histopathologic results of long-term sildenafil administration on rat inner ear

OBJECTIVES

Sildenafil, a selective inhibitor of phosphodiesterase type 5, is widely used for the treatment of erectile dysfunction. Although cochlear effects of phosphodiesterase type 5 inhibitors remain still unclear because of inadequate data, some evidence that recently emerged indicates that these medications may be responsible for hearing impairment. In the present study, we aimed to examine the histopathologic effects of long-term sildenafil use on the cochlea in a rat model.

METHODS

The study was performed with adult male Wistar albino rats. The control group was fed on standard laboratory diet. The study group was applied orally with sildenafil therapy, 1.5 mg/kg once a day for 45 days. Rats were anesthetized and decapitated. Each temporal bone was dissected, and the cochleas were removed en bloc. The inner-ear biopsy specimens were examined histologically with hematoxylin and eosin and caspase 3 immunoreaction under light microscopy.

RESULTS

Hematoxylin and eosin staining showed no distinctive difference between the control group and the sildenafil group. With immunohistochemical examination, caspase 3 immunoreactivity was observed in the sildenafil group. In the control group, caspase 3 immunoreactivity was not observed.

CONCLUSIONS

The caspase 3 immunoreactivity in the sildenafil group was strongly associated with an increase in apoptotic events in the cochlea. Long-term use of sildenafil can cause hearing impairment through increased apoptosis.

Hemodynamic effects of sildenafil citrate (Viagra) on segmental branches of bilateral renal arteries

INTRODUCTION

Erectile dysfunction (ED) is one of the most encountered male health problem and sildenafil citrate is used worldwide for treatment of ED. Aim of the present study was to determine and evaluate hemodynamic effects of sildenafil citrate on segmental branches of bilateral renal arteries of cases with ED.

PATIENTS AND METHODS

Total of 35 male patients aging between 34 and 56 years were recruited into study. Patients were evaluated with renal color Doppler sonography (CDS) before and after (45-75 min) peroral sildenafil citrate (50 mg) administration. Peak systolic flow rate (V(max)), end diastolic flow rate (V(min)), resistive index (RI) and pulsatility index (PI) of renal artery segmental branches were determined before and after sildenafil citrate administration.

RESULTS

V(min) measured at right lower segment was significantly reduced after sildenafil administration (p = 0.030). Accordingly mean RI and PI of right lower segment of renal artery slightly increased after drug administration (p = 0.007 and p = 0.012, respectively). The measurements on other segments had no significant change after sildenafil treatment when compared to baseline values. On this single dose administration no side effect was recorded.

CONCLUSION

Findings of the present study demonstrated that peroral sildenafil citrate usage had slight effects on hemodynamic parameters of lower segmental branch of right renal artery. This result could not be interpreted as robust evidence for hemodynamic changes of renal arteries associated with sildenafil usage nevertheless warrants more comprehensive research with larger number of patients.

Sildenafil in erectile dysfunction: a critical review

Sildenafil citrate (Viagra) is a potent orally active cGMP-specific phosphodiesterase type 5 (PDE5) inhibitor that is effective as a peripheral conditioner in the treatment of male erectile dysfunction (ED) of organic, psychogenic or mixed aetiology. Sildenafil is the first effective oral agent in the management of ED that has had a revolutionary impact on management of ED. The present review has been subdivided into five major sections. Based on the most recent peer-reviewed publications, the first section is aimed at critically evaluating PDE5 selectivity as well as the pharmacokinetics and pharmacodynamics of the drug, mainly to assess the best doses for each group of patients (i.e. adult and elderly men). Effectiveness in a broad spectrum ED population is the subject of the second section of the review, principally reporting post-marketing company-independent results. Safety and tolerability are the key concerns of the third section, with a broad consideration of the most commonly reported adverse events. Special attention has been paid to the cardiovascular safety of the drug, chiefly outlining the positive and potentially protective cardiac effects of sildenafil. Moreover, the impact of sildenafil in special patient populations is considered, namely in men complaining of diabetes mellitus, depression, neurological disorders, renal failure and those who have undergone a radical prostatectomy. Sildenafil and the ageing male has been especially underlined. Finally, the review covers a few new potential applications of sildenafil in ED patients with regard to high-dose treatment and combination therapy. The review ends with several considerations regarding the direct and/or indirect impact of sildenafil over quality of life and quality of partnership.