Daily dosing of PDE5 inhibitors: where does it fit in?

Diagnostic and Therapeutic Workup of Erectile Dysfunction: Results From a Delphi Consensus of Andrology Experts

INTRODUCTION

Erectile dysfunction is a highly prevalent condition. Existing guidelines provide recommendations for diagnosis and treatment, but they are often disregarded in clinical practice in favor of a "patient-tailored" approach.

OBJECTIVES

We planned a Delphi consensus method to bridge the gap between evidence-based medicine and the real-life approach in daily practice.

MATERIALS AND METHODS

The Advisory Board prepared 15 statements on debated topics in andrology, each including 4-6 items designed as a 5-point Likert scale. After a validation phase, the questionnaire was sent by e-mail to a panel of experts for a first round of voting; members of the panel were later invited to a second round of voting, preceded by discussion of the "hot topics" identified in the first round.

RESULTS

The first round of the Delphi consensus involved 101 experts; 71 (70%) also took part in the second round of voting. The Advisory Board deemed 22 items to be worthy of debate, and these underwent the second round of voting. "Real-life" results from the survey proved quite different from evidence-based recommendations.

CONCLUSION

Although guidelines suggest the best approach for a "standard" patient, real-life settings require flexibility. Diagnostic and therapeutic approaches should be tailored to the patients' needs. Phosphodiesterase type 5 inhibitors are recognized as the first-line therapy in both settings, including the newly introduced sildenafil orodispersible film. Indications from the panel might help close the gap between recommendations from guidelines and real-life practice in relation to the diagnosis and treatment of erectile dysfunction. Isidori AM, Giammusso B, Corona G, et al. Diagnostic and Therapeutic Workup of Erectile Dysfunction: Results From a Delphi Consensus of Andrology Experts. Sex Med 2019;7:292-302.

Early administration of phosphodiesterase 5 inhibitors after induction of diabetes in a rat model may prevent erectile dysfunction

BACKGROUND

The possible role of phosphodiesterase 5 inhibitors (PDE5Is) in prevention of negative effect of diabetes mellitus (DM) on erectile function is not well settled.

OBJECTIVES

To investigate the effect of early administration of vardenafil on erectile function, cavernosal structure, and genes expression in a rat model of DM.

MATERIALS AND METHODS

This experimental study was carried out at Suez Canal University's research laboratory. This study was conducted on a total of 60 adult male Albino Wistar rats, aged 60-80 days and weighing an average of 200 g. Rats were equally divided into six groups of 10 rats each: Group I (sham); Group II (DM with no treatment); Groups III, IV, V, and VI received vardenafil started at day 1, week 4, week 8, and week 12 after induction of DM, respectively. Functional study assessment of all groups was performed before euthanization, and then tissues were harvested for histopathological, ultrastructural, and molecular examinations.

RESULTS

There was a significant difference of intracavernosal pressure between early (94 ± 2.18) and late (40.5 ± 1.94) treatment groups (p = 0.011). Histopathological and ultrastructural changes of DM with no treatment and late treatment groups showed distorted cavernous architecture and extensive fibrosis. There was significant difference of smooth muscle to collagen ratio between early and late treatment groups (p = 0.035). There was significant upregulation of nNOS(p = 0.021) and iNOS (p = 0.047) in early vs. late treatment group. The difference was insignificant in eNOS (p = 0.386) or TGF-β1(p = 0.149).

DISCUSSION AND CONCLUSION

Early treated rats with vardenafil had preserved erection and normal cavernosal structure, ultrastructure and gene expression of iNOS, nNOS, eNOS, and TGF-β1. Quantification of gene expression would improve our knowledge regarding cytokines expression and molecular background of DM-associated ED. Clinical application of this result may encourage early administration of PDE5I to prevent deleterious effects of DM on erectile function in newly diagnosed DM patients with probable uncontrolled blood glucose.

The two phases of the clinical validation of preclinical translational mechanistic research on PDE5 inhibitors since Viagra's advent. A personal perspective

The FDA approval of Viagra (sildenafil) for the on demand treatment of erectile dysfunction (ED) through relaxation of the corporal and cavernosal vascular smooth muscle that results in an increase in blood flow to the corporal tissues stemmed from 2 decades of research, mainly at academic centers. This culminated in the finding of the nitric oxide/cGMP pathway as the mediator of penile erection, followed by some years of basic studies and clinical validation at Pfizer. Further on, new translational laboratory and animal research from our group initiated a second phase when we proposed an alternative therapeutic schedule and mechanism of action for PDE5 inhibitors (PDE5i) in both corporal veno-occlusive dysfunction (CVOD) and Peyronie's disease (PD), specifically, continuous long-term administration (CLTA) to achieve sustained levels of cGMP within the penis. Due to the extended half-life of the long-acting PDE5i, tadalafil, this new alternative encompasses preferentially daily administration, although shorter half-life PDE5i, like sildenafil and vardenafil work too, depending on the duration, dose, and frequency of their administration This novel use was initially supported by showing the antifibrotic/antioxidant effects of nitric oxide and cGMP, produced by the induction of iNOS, as a mechanism of defense against collagen deposition in the localized fibrotic plaque of PD in an avascular tissue, the tunica albuginea. Our studies on iNOS and the progressive diffuse fibrosis occurring in the smooth muscle in CVOD, led to proposing the CLTA of PDE5i for maintaining sustained cGMP levels both in PD and in CVOD in order to halt or regress the penile fibrosis. In CVOD, we showed that PDE5i protect the corporal smooth muscle and reduce myofibroblast activation and number, counteracting the underlying corporal tissue pathology that causes CVOD, and potentially ameliorating long-term CVOD or even curing it. This review is focused on this novel PDE5i anti-fibrotic therapeutic concept.

Non-invasive Management Options for Erectile Dysfunction When a Phosphodiesterase Type 5 Inhibitor Fails

Phosphodiesterase type 5 inhibitors (PDE5Is) are the drug of choice for medical management of erectile dysfunction (ED). On-demand PDE5Is have an overall efficacy of 60-70% for ED; 30-35% of patients fail to respond to a PDE5I, and 30-50% of non-responders can be salvaged with detailed counseling on proper use and physician follow-up to ensure that the patient has been prescribed an appropriate and full PDE5I clinical trial. True non-responders may be offered intracavernosal injections of erectogenic drugs, intraurethral alprostadil, or surgical insertion of a penile prosthesis. Such options are not discreet and are associated with more adverse effects than PDE5Is. Thus patients may request additional non-invasive medical management options. This review describes published literature on patients who failed to respond to an on-demand PDE5I regimen and were treated with a non-invasive PDEI-based regimen, including switching from one PDE5I to another; increasing the dose of PDE5I above the labeled dosage range; using two PDE5Is concurrently; using a daily PDE5I regimen; or combining a PDE5I with a testosterone supplement, α-adrenergic antagonist, intraurethral or intracavernosal alprostadil, vacuum erection device, or low-intensity shock wave therapy. The limitations of published clinical trials do not allow for sufficient evidence to recommend one option over another. Therefore, in PDE5I-refractory patients, the choice of a specific next step should be individualized based on the preference of the patient and his sexual partner, the advantages and disadvantages of the various options, the concurrent medical illnesses and medications of the patient, and the patient's response to treatment.

[Continuous use of PDE5 inhibitors in the treatment of erectile dysfunction: New insights and opportunities]

At present, there is debate regarding the continuous use of phosphodiesterase 5 inhibitors in the treatment of erectile dysfunction. Cumulative evidence supports the benefit, even at low doses, thatcontinuous treatment has on erectile function -even in difficult-to-treat patients-, and on the spontaneity and naturalness of sexual relationships. Safety and tolerability have also proven to be good. Beyond phosphodiesterase 5 inhibition, the effect of continuous treatment of erectile function appears to be based on improvement of endothelial function and oxygenation of the penile vascular bed as a result of the increased number of erections, hence playing down the importance of pharmacokinetics. Although evidence is still limited, this new scenario opens new paths for the treatment of erectile dysfunction patients in whom on-demand treatments are not effective or deemed appropriate, and would benefit the spontaneity of sexual life.