Non-responders to phosphodiesterase type 5 inhibitors: is there a second chance?

Long Term Effectiveness and Safety of Intracavernosal Botulinum Toxin A as an Add-on Therapy to Phosphosdiesterase Type 5 Inhibitors or Prostaglandin E1 Injections for Erectile Dysfunction

BACKGROUND

Some evidence suggests that intracavernosal botulinum toxin A (BTX-A IC) injections administered in addition to phosphodiesterase type 5 inhibitors (PDE5-Is) or prostaglandin E1 intracavernosal injections (PGE1 ICI) could effectively treat erectile dysfunction (ED) in non-responders, or insufficient responders to these pharmacologic treatments.

AIM

To determine the long-term effectiveness and safety of combined treatment involving a single injection of BTX-A IC as an add on therapy to PDE5-Is or PGE1-ICI for the treatment of ED of different etiologies.

METHODS

A retrospective, uncontrolled, single center study was conducted. Data from 123 consecutive patients with ED who were insufficient responders to PDE5-Is or PGE1-ICI and who received onabotulinumtoxinA 100 U, abobotulinumtoxinA 250 U or 500 U IC as an add on to their current pharmacologic treatment were analyzed. All analyses were exploratory. Qualitative data were compared using the Fisher's exact test. Univariate and multivariate analysis were performed using logistic regression with Odds Ratios (OR). Only variables with P < .05 in the univariate analysis were selected for multivariate analysis.

RESULTS

The minimally clinically important difference (relative to baseline severity of ED) in the International Index of Erectile Function-Erectile function domain (IIEF-EF) score was achieved in 50% of patients at 34 (27-42) days and in 41% at 5.9 (3.9 - 8.1) months following BTX-A IC in combination with PDE5-Is or PGE1 ICI. The severity of ED influenced response to BTX-A IC according to the multivariate analysis (OR = 0.3, IC(95%]) = (0.16 - 0.56). Neither being post prostatectomy nor the type of BTX-A affected the response. Effectiveness tended to decrease more over time with abobotulinumtoxinA 250 U than 500 U.The only side-effects were mild penile pain on injection (n = 1) and mild penile pain for 3 days following injection (n = 1); no systemic effects were reported.

CLINICAL IMPLICATIONS

BTX-A IC (all types) administered as an add on to registered pharmacologic treatments improved erectile function for at least 6 months in 41% of patients with ED of varying etiologies, and was safe.

STRENGTHS & LIMITATIONS

A relatively large cohort of patients with ED was included, with a long follow-up period, however the study was retrospective, and uncontrolled.

CONCLUSION

This study provides preliminary evidence that BTX-A IC administered as an add-on therapy for ED that is insufficiently responsive to standard therapy is effective for at least 6 months, and is safe. Randomized clinical trials are now needed to fully confirm these results.

Safety and Efficacy of Intracavernosal Injections of AbobotulinumtoxinA (Dysport®) as Add on Therapy to Phosphosdiesterase Type 5 Inhibitors or Prostaglandin E1 for Erectile Dysfunction-Case Studies

Erectile dysfunction (ED) is a highly prevalent condition with a variety of possible risk factors and/or etiologies. Despite significant advances regarding ED pharmacological management, there are still insufficient responders to existing pharmacological treatments e.g., approximately 30% of patients are insufficient responders to phosphodiesterase type 5 inhibitors (PDE5-Is). It has been recently proposed that botulinum toxin A intracavernosally (IC) delivered could be effective in these patients. Data from a retrospective uncontrolled single center study of 47 ED patients, consecutively recruited, insufficient responders to existing pharmacological treatments e.g., PDE5-Is or IC PGE1 injections treated with IC abobotulinumtoxinA 250 or 500 U as free combination with their existing treatment have been analyzed. Response rate, according to the International Index of Erectile Function-Erectile Function domain score, 6 weeks following IC abobotulinumtoxinA in combination with prior pharmacological treatment, was 54%. Two patients have reported mild penile pain on injection or during the 3 days following injection. Therapeutic efficacy did not seem to be influenced by the etiologies and/or risk factors for ED. Conversely, the less severe ED, the higher the response rate. Preliminary evidence for the therapeutical potential with acceptable safety of IC abobotulinumtoxinA as add-on therapy for ED not sufficiently responsive to standard therapy should be confirmed in randomized clinical trials.

An update on pharmacological treatment of erectile dysfunction with phosphodiesterase type 5 inhibitors

INTRODUCTION

Phosphodiesterase type 5 inhibitors (PDE5-i) are used for the oral treatment of erectile dysfunction (ED). Since the launch of sildenafil more than 15 years ago, new molecules have become available. At present, in addition to tadalafil and vardenafil, there are three other drugs, udenafil, avanafil and mirodenafil, marketed in some countries which appear to be promising.

AREAS COVERED

The clinical pharmacological differences in dosage and side effects of all PDE5-i are evaluated.

EXPERT OPINION

All PDE5-i are equally effective and safe for the treatment of ED. On-demand use of any PDE5-i is also safe for patients with comorbid conditions. Tadalafil seems to be the preferred drug by patients and physicians, probably due to its peculiar pharmacological profile that makes sexual intercourse more spontaneous for the patients. Preliminary data suggest that the use of vardenafil may also be beneficial in cases of ED associated with premature ejaculation. Daily treatment is another option in men with ED and documented vascular or prostate disease. In geriatric or in difficult-to-treat populations, the evaluation of testosterone plasma levels will help to predict the efficacy of any PDE5-i. Remarkably, when such drugs are withdrawn for any reason, ED most often continues to occur because of the presence of an underlying disease.

A new era in the treatment of erectile dysfunction: chronic phosphodiesterase type 5 inhibition

Historically, oral phosphodiesterase type 5 inhibitors (PDE5-i) have been prescribed with an 'as-necessary' regimen for treating erectile dysfunction (ED), thus addressing primarily symptom relief. However, approximately 30% of patients are unresponsive to on-demand PDE5-i regimens due to both psychogenic and organic factors and, although it is difficult to estimate the proportion, discontinuation rates remain high. In recent years, a 2.5-5 mg daily dose of tadalafil has been proposed and was recently approved for treating ED. Chronic PDE-5 inhibition has the advantage of potentially 'curing' ED, on a daily basis, by interfering with pathophysiological factors of both psychogenic (anxiety related to planning sexual activity) and organic (endothelial dysfunction, penile structural homeostasis) origin, although further research is needed to better address these hypotheses. Clinical studies showed that chronic PDE5-i regimens are a safe and effective alternative to the classical on-demand dosage, and might improve the outcomes in a selected group of patients.