ORIGINAL RESEARCH—ED PHARMACOTHERAPY: Efficacy and Tolerability of Lodenafil Carbonate for Oral Therapy of Erectile Dysfunction: A Phase III Clinical Trial

Synthetic approaches and clinical application of representative small-molecule inhibitors of phosphodiesterase

Phosphodiesterases (PDEs) constitute a family of enzymes that play a pivotal role in the regulation of intracellular levels of cyclic nucleotides, including cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP). Dysregulation of PDE activity has been implicated in diverse pathological conditions encompassing cardiovascular disorders, pulmonary diseases, and neurological disorders. Small-molecule inhibitors targeting PDEs have emerged as promising therapeutic agents for the treatment of these ailments, some of which have been approved for their clinical use. Despite their success, challenges such as resistance mechanisms and off-target effects persist, urging continuous research for the development of next-generation PDE inhibitors. The objective of this review is to provide an overview of the synthesis and clinical application of representative approved small-molecule PDE inhibitors, with the aim of offering guidance for further advancements in the development of novel PDE inhibitors.

An overview of conventional and investigational phosphodiesterase 5 inhibitors for treating erectile dysfunction and other conditions

INTRODUCTION

There is a rising concern about developing innovative, efficacious PDE5I molecules that provide better safety, efficacy, and tolerability with less adverse effects. Innovative PDE5I with dual targets have also been defined in the literature. Additionally, some of PDE5I are able to selectively inhibit other enzymes such as histone deacetylase, acetylcholine esterase, and cyclooxygenase or act as nitric oxide donors. This review presents knowledge concerning the advanced trends and perspectives in using PDE5I in treatment of ED and other conditions.

AREAS COVERED

Pre-clinical and early clinical trials that investigated the safety, efficacy, and tolerability of novel PDE5I such as Udenafil, Mirodenafil, Lodenafil, Youkenafil, Celecoxib, and TPN729 in treatment of ED and other conditions.

EXPERT OPINION

Preclinical and limited early clinical studies of the new molecules of PDE5I have demonstrated encouraging results; however, safety, efficacy, and tolerability are still issues that necessitate further long-term multicenter clinical studies to ensure justification of their uses in treatment of ED and other conditions. Progress in molecular delivery techniques and tailored patient-specific management and additional therapeutic technology will dramatically improve care for ED and other conditions. The dream of ED and many other conditions becoming more effectively managed may be feasible in the near future.

Phosphodiesterase 5 inhibitors: preclinical and early-phase breakthroughs for impotence treatments

INTRODUCTION

Erectile dysfunction (ED) is a condition that affects millions of men worldwide and is characterized by the inability to achieve or maintain an erection for satisfactory sexual performance. There are numerous treatment options for ED, including medications, mechanical assist devices, and surgical management; however, first-line treatment is usually a phosphodiesterase 5 (PDE5) inhibitor. There is a growing interest in developing novel, efficacious PDE5 inhibitors that provide better quality, safety, and tolerability profiles with less adverse effects. Our review of udenafil, mirodenafil, youkenafil, lodenafil, and SLx-2101 analyzes the safety, efficacy, and pharmacokinetic properties of these new ED drugs.

AREAS COVERED

Clinical trials demonstrated improved scores in questionnaires, such as the International Index of Erectile Function and Sexual Encounter Profile, for udenafil, mirodenafil, and lodenafil, while youkenafil and SLx-2101 revealed enhanced safety and tolerability in early pharmacokinetic studies.

EXPERT OPINION

It is our opinion that more robust clinical trials are required before these medications can be made available in the United States. Additionally, the field of urology may benefit from pursuing other avenues of pharmacotherapy, such as injections, tablets with a different mechanism of action, or stem cell therapy, to restore the integrity of the endothelium within the penis.

Erectile Dysfunction: Treatments, Advances and New Therapeutic Strategies

Erectile dysfunction (ED) is the inability to get and maintain an adequate penile erection for satisfactory sexual intercourse. Due to its negative impacts on men's life quality and increase during aging (40% of men between 40 and 70 years), ED has always attracted researchers of different disciplines, from urology, andrology and neuropharmacology to regenerative medicine, and vascular and prosthesis implant surgery. Locally and/or centrally acting drugs are used to treat ED, e.g., phosphodiesterase 5 inhibitors (first in the list) given orally, and phentolamine, prostaglandin E1 and papaverine injected intracavernously. Preclinical data also show that dopamine D4 receptor agonists, oxytocin and α-MSH analogues may have a role in ED treatment. However, since pro-erectile drugs are given on demand and are not always efficacious, new strategies are being tested for long lasting cures of ED. These include regenerative therapies, e.g., stem cells, plasma-enriched platelets and extracorporeal shock wave treatments to cure damaged erectile tissues. Although fascinating, these therapies are laborious, expensive and not easily reproducible. This leaves old vacuum erection devices and penile prostheses as the only way to get an artificial erection and sexual intercourse with intractable ED, with penile prosthesis used only by accurately selected patients.

Bibliometric and visualization analysis of literature relating to diabetic erectile dysfunction

Introduction

Diabetic erectile dysfunction (DMED) refers to erectile dysfunction secondary to diabetes. Erectile dysfunction is characterized by a persistent inability to achieve and maintain an erection sufficient to permit satisfactory sexual activity.

Methods

Based on the Web of Science core collection database, we firstly analyzed the quantity and quality of publications in the field of DMED, secondly profiled the publishing groups in terms of country, institution, author's publication and cooperation network, and finally sorted out and summarized the hot topics of research.

Results

From 2001 to 2022, a total of 1,403 articles relating to this topic were published in 359 journals. They represent the global research status, potential hotspots, and future research directions. The number of DMED-related publications and citations has steadily increased over the few past decades. Academic institutions from Europe and the United States have played a leading role in DMED research. The country, institution, journal, and author with the most publications were the United States (294), INHA University (39), the Journal of Sexual Medicine (156), and Ryu, Ji-Kan (29), respectively. The most common keywords were erectile dysfunction (796), men (256), diabetes (254), diabetes mellitus (239), prevalence (180), corpus cavernosum (171), dysfunction (155), mellitus (154), nitric-oxide synthase (153), and expression (140). The main keyword-based research topics and hotspots in the DMED field were oral sildenafil, smooth muscle relaxation, nitric oxide synthase, gene therapy, metabolic syndrome, cavernous nerve injury, stem cell, and penile prosthesis.

Discussion

The terms oral sildenafil, smooth muscle relaxation, nitric oxide synthase, gene therapy, metabolic syndrome, cavernous nerve injury, stem cell, and penile prosthesis will be at the forefront of DMED-related research.

A validated LC-MS/MS assay for the quantification of phosphodiesterase-5 inhibitors in human plasma

Phosphodiesterase inhibitors (PDE5i) are considered the first line therapy for erectile dysfunction. All PDE5i available on the market are structurally related; their main differences relate to their pharmacokinetic parameters. For these treatments to be effective and safe, it is necessary that these drugs are in the appropriate doses and that they reach adequate concentrations in the plasma. For this purpose, it is essential to perform therapeutic monitoring using bioanalytical methods. In this way, the present work aimed to develop and validate a new bioanalytical method, based on LC-MS/MS, for the simultaneous quantification of six commercially available PDE5i (avanafil, lodenafil, sildenafil, tadalafil, udenafil, and vardenafil). For this purpose, the human plasma was extracted with diethyl ether and sulfaquinoxaline was established as an internal standard. Separation was achieved using an Xbridge C18 column at 40 °C as the stationary phase, using water and acetonitrile as the mobile phase (both with formic acid and ammonium formate) in gradient mode. The method was validated according to the current guidelines and was found to be selective, linear (from 1 to 200 ng.mL^-1 for all drugs except for tadalafil which is from 5 to 200 ng.mL^-1), precise, accurate, and free of residual and matrix effects. The drugs were considered stable in plasma and in solution under different conditions. The method was applied to volunteerssamples, demonstrating that the method can be used routinely and may be useful in future studies on pharmacokinetics and therapeutic monitoring.

Antinociceptive Effect of Lodenafil Carbonate in Rodent Models of Inflammatory Pain and Spinal Nerve Ligation-Induced Neuropathic Pain

Introduction

New therapeutic alternatives for pain relief include the use of phosphodiesterase-5 (PDE5) inhibitors, which could prevent the transmission of painful stimuli by neuron hyperpolarization via nitric oxide (NO)/cyclic 3',5'-guanosine monophosphate (cGMP) pathway. The present work investigated the antinociceptive activity of a new PDE5 inhibitor, lodenafil carbonate, in inflammatory and neuropathic pain models.

Methods and Results

Although no effect was detected on neurogenic phase of formalin test in mice, oral administration of lodenafil carbonate dose-dependently reduced reactivity in the inflammatory phase (200.6 ± 39.1 to 81.9 ± 18.8 s at 10 μmol/kg, p= 0.0172) and this effect was totally blocked by NO synthase inhibitor, L-Nω-nitroarginine methyl ester (L-NAME). Lodenafil carbonate (10 μmol/kg p.o.) significantly reduced nociceptive response as demonstrated by increased paw withdrawal latency to thermal stimulus (from 6.8 ± 0.7 to 10.6 ± 1.3 s, p= 0.0006) and paw withdrawal threshold to compressive force (from 188.0 ± 14.0 to 252.5 ± 5.3 g, p<0.0001) in carrageenan-induced paw inflammation model. In a spinal nerve ligation-induced neuropathic pain, oral lodenafil carbonate (10 μmol/kg) also reversed thermal hyperalgesia and mechanical allodynia by increasing paw withdrawal latency from 17.9 ± 1.5 to 22.8 ± 1.9 s (p= 0.0062) and paw withdrawal threshold from 26.0 ± 2.8 to 41.4 ± 2.9 g (p= 0.0196). These effects were reinforced by the reduced GFAP (3.4 ± 0.5 to 1.4 ± 0.3%, p= 0.0253) and TNF-alpha (1.1 ± 0.1 to 0.4 ± 0.1%, p= 0.0111) stained area densities as detected by immunofluorescence in ipsilateral dorsal horns.

Conclusion

Lodenafil carbonate demonstrates important analgesic activity by promoting presynaptic hyperpolarization and preventing neuroplastic changes, which may perpetuate chronic pain, thus representing a potential treatment for neuropathic pain.

Phosphodiesterases 5 Inhibitors and Erectile Dysfunction Recovery after Pelvic Surgery: Future Perspectives for New Drugs and New Formulations

BACKGROUND

Phosphodiesterase 5 inhibitors (PDE5I) represent the first-line treatment in the management of post-operative erectile dysfunction (ED) after pelvic oncological surgery. The aim of our study is to evaluate the available evidence on the efficacy of PDE5Is, including new formulations and penile rehabilitation post-pelvic surgery.

EVIDENCE ACQUISITION

A systematic review of the literature was performed until May 2020. The following databases were searched: Scopus, Medline and Web of Science. The MeSH search was conducted by combining the following terms: 'erectile dysfunction', 'radical prostatectomy' 'pelvic' 'bladder' 'phosphodiesterase' inhibitors' 'avanafil' 'sildenafil' 'tadalafil' 'lodenafil' 'mirodenafil' 'udenafil' 'vardenafil' 'sublingual' 'orodispersible' 'penile' 'rehabilitation'.

EVIDENCE SYNTHESIS

Sildenafil, Tadalafil, vardenafil and Avanafil improve EF compared with placebo in men with all levels of ED severity after radical prostatectomy with good tolerability. No specific recommendations can be suggested regarding the superiority of a drug over the other. The optimal dose, continuous vs. on-demand and duration of treatment, is still under investigation. In vitro and preclinical studies suggest the possible role for lodenafil, mirodenafil and oro-dispersible formulations in patients undergoing oncological pelvic surgery. Few studies demonstrated the efficacy of udenafil in improving ED after rectal surgery or radical prostatectomy. Complete recovery of EF after surgery is still an unmet need in the field of penile rehabilitation after pelvic surgery.

CONCLUSION

PDE5Is have a crucial role in the management of post pelvic surgery of ED. New drugs and new formulations have shown excellent results in patients with ED; however, data in patients after surgery is still scarce. Further well designed RCT should clarify the role of these new compounds and oro-dispersible formulations in the management of ED in patients undergoing pelvic surgery.

The Use of Vasoactive Drugs in the Treatment of Male Erectile Dysfunction: Current Concepts

It is widely accepted that disorders of the male (uro)genital tract, such as erectile dysfunction (ED) and benign diseases of the prostate (lower urinary tract symptomatology or benign prostatic hyperplasia), can be approached therapeutically by influencing the function of both the vascular and non-vascular smooth muscle of the penile erectile tissue or the transition zone/periurethral region of the prostate, respectively. As a result of the discovery of nitric oxide (NO) and cyclic guanosine monophosphate (GMP) as central mediators of penile smooth muscle relaxation, the use of drugs known to increase the local production of NO and/or elevate the intracellular level of the second messenger cyclic GMP have attracted broad attention in the treatment of ED of various etiologies. Specifically, the introduction of vasoactive drugs, including orally active inhibitors of the cyclic GMP-specific phosphodiesterase (PDE) 5, has offered great advantage in the pharmacotherapy of ED and other diseases of the genitourinary tract. These drugs have been proven efficacious with a fast on-set of action and an improved profile of side-effects. This review summarizes current strategies for the treatment of ED utilizing the application of vasoactive drugs via the oral, transurethral, topical, or self-injection route.

Drug delivery options and therapeutic advances in the management of erectile dysfunction

INTRODUCTION

Erectile dysfunction (ED) is defined as the inability to achieve or maintain an erection sufficient for satisfactory sexual performance. It is estimated that 20-30% of adult men will have at least one episode of ED during their lifetime and the prevalence increases with age. ED is known to have significant negative psychological implications for men, resulting in impaired functional status and a greater prevalence of anxiety and depression.

AREAS COVERED

Medications for the treatment of erectile dysfunction largely revolve around oral, injection, and topical therapies. Though all three modalities are widely used, each delivery option has its own advantages and specific indications. Likewise, there are several new developing treatments for ED that may change the landscape of treatment. The goal of this review is to summarize contemporary drug delivery options used in the treatment of ED and highlight future promising pharmacological developments.

EXPERT OPINION

There are a myriad of new developments on the horizon including new PDE5Is and drug targets, nanotechnology enhancements, stem cell and gene therapy, shockwave therapy, and platelet-rich plasma injections. These are all promising new methods to not only treat ED but also to address the pathology and prevent or eliminate further damage.

Current Concepts on the Reno-Protective Effects of Phosphodiesterase 5 Inhibitors in Acute Kidney Injury: Systematic Search and Review

Acute kidney injury (AKI) is associated with increased morbidity, prolonged hospitalization, and mortality, especially in high risk patients. Phosphodiesterase 5 inhibitors (PDE5Is), currently available as first-line therapy of erectile dysfunction in humans, have shown a beneficial potential of reno-protection through various reno-protective mechanisms. The aim of this work is to provide a comprehensive overview of the available literature on the reno-protective properties of PDE5Is in the various forms of AKI. Medline was systematically searched from 1946 to November 2019 to detect all relevant animal and human studies in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) statement. In total, 83 studies were included for qualitative synthesis. Sildenafil is the most widely investigated compound (42 studies), followed by tadalafil (20 studies), icariin (10 studies), vardenafil (7 studies), zaprinast (4 studies), and udenafil (2 studies). Even though data are limited, especially in humans with inconclusive or negative results of only two clinically relevant studies available at present, the results of animal studies are promising. The reno-protective action of PDE5Is was evident in the vast majority of studies, independently of the AKI type and the agent applied. PDE5Is appear to improve the renal functional/histopathological alternations of AKI through various mechanisms, mainly by affecting regional hemodynamics, cell expression, and mitochondrial response to oxidative stress and inflammation.

Placebo Responses Among Men With Erectile Dysfunction Enrolled in Phosphodiesterase 5 Inhibitor Trials: A Systematic Review and Meta-analysis

IMPORTANCE

Placebo responses in the treatment of erectile dysfunction (ED) are poorly described in the literature to date.

OBJECTIVE

To quantify the association of placebo with ED outcomes among men enrolled in placebo-controlled, phosphodiesterase 5 inhibitor (PDE5I) trials.

DATA SOURCES

For this systematic review and meta-analysis, a database search was conducted to identify double-blind, placebo-controlled studies using PDE5Is for the treatment of ED published from January 1, 1998, to December 31, 2018, within MEDLINE, Embase, Cochrane Library, and Web of Science. Only articles published in the English language were included.

STUDY SELECTION

Double-blind, placebo-controlled randomized clinical trials of PDE5Is for ED were included. Studies were excluded if they did not provide distribution measures for statistical analysis. Study selection review assessments were conducted by 2 independent investigators. A total of 2215 studies were identified from the database search, and after review, 63 studies that included 12 564 men were analyzed.

DATA EXTRACTION AND SYNTHESIS

Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines were followed in abstracting data and assessing validity. Data were extracted from published reports by 2 independent reviewers. Quality assessment was performed using the Jadad scale. Data were pooled using a random-effects model.

MAIN OUTCOMES AND MEASURES

The main outcome was improvement in the erectile function domain of the International Index of Erectile Function questionnaire in the placebo arm of the included studies. Effect size was reported as bias-corrected standardized mean difference (Hedges g). The hypothesis was formulated before data extraction.

RESULTS

A total of 63 studies that included 12 564 men (mean [SD] age, 55 [7] years; age range, 36-68 years) were included. Erectile function was significantly improved among participants in the placebo arm, with a small to moderate effect size (Hedges g [SE], 0.35 [0.03]; P < .001). Placebo effect size was larger among participants with ED associated with posttraumatic stress disorder (Hedges g [SE], 0.78 [0.32]; P = .02) compared with the overall analysis. No significant difference was found between placebo and PDE5Is for ED after prostate surgery or radiotherapy (Hedges g [SE], 0.30 [0.17]; P = .08).

CONCLUSIONS AND RELEVANCE

In this study, placebo was associated with improvement of ED, especially among men with ED-related posttraumatic stress disorder. No difference was found between placebo and PDE5I among men treated for ED after prostate surgery.

The safety and efficacy of PDE5-inhibitors-vardenafil on treating diabetes mellitus erectile dysfunction: A protocol for systematic review and meta analysis

BACKGROUND

Diabetic mellitus erectile dysfunction (DMED) refers to erectile dysfunction (ED) secondary to diabetes. As people's lifestyle changes and the population ages, the incidence of DMED continues to increase. Many clinical trials have proven that PDE5-inhibitors-vardenafil has a significant effect in the treatment of Diabetic mellitus erectile dysfunction. In this systematic review, we aim to evaluate the effectiveness and safety of PDE5-inhibitors-vardenafil for Diabetic mellitus erectile dysfunction.

METHODS

We will search PubMed, Cochrane Library, AMED, EMbase, WorldSciNet; Nature, Science online and China Journal Full-text Database (CNKI), China Biomedical Literature CD-ROM Database (CBM), and related randomized controlled trials included in the China Resources Database. The time is limited from the construction of the library to February 2019.We will use the criteria provided by Cochrane 5.1.0 for quality assessment and risk assessment of the included studies, and use the Revman 5.3 and Stata13.0 software for meta-analysis of the effectiveness, recurrence rate, and symptom scores of Diabetic mellitus erectile dysfunction.

ETHICS AND DISSEMINATION

This systematic review will evaluate the efficacy and safety of PDE5-inhibitors-vardenafil for treating Diabetic mellitus erectile dysfunction. Because all of the data used in this systematic review and meta-analysis has been published, this review does not require ethical approval. Furthermore, all data will be analyzed anonymously during the review process Trial.

TRIAL REGISTRATION NUMBER

PROSPERO CRD42018095185.

Efficacy and safety of PDE5 inhibitors in the treatment of diabetes mellitus erectile dysfunction: Protocol for a systematic review

INTRODUCTION

Diabetes mellitus erectile dysfunction (DMED) is a common complication of long-term hyperglycemia. With the increasing of diabetic patients, the number of DMED patients is gradually growing up, which has a serious impact on the quality of life of patients. PDE5 inhibitors have good clinical efficacy in DMED patients. This study is designed to evaluate the efficacy and safety of PDE5 inhibitors in DMED patients.

METHODS AND ANALYSIS

We will systematically search all randomized controlled trials (RCTs) by electronic and manual search. Electronic retrieval of the database includes Pubmed, EMBASE, The Cochrane Library, the Chinese BioMedical Literature Database, the China National Knowledge Infrastructure (CNKI), the China Science and Technology Journal database (VIP) and the Wanfang database. Manual search will retrieve gray literature, including dissertations, ongoing experiments, grey literature, conference and unpublished documents. We use the IIEF-5 scale as the primary outcome of DMED. We also need to pay attention to the following outcomes: the sexual satisfaction of patients and their partners, like IIEF Q3 Q4; SEP 2, 3; GAQ. More importantly, the adverse reactions of patients during medication will also be taken seriously. Two reviewers will independently read the articles, extract the data information, and give the assessment of risk of bias. Data analysis will be used the special software like RevMan (version 5.3.5), ENDNOTE X7 and STATA 13.

RESULTS

This study will provide a comprehensive assessment based on current evidence of PDE5 inhibitors for DMED, especially its impacts on International Index of Erectile Function, the sexual satisfaction of patients and their partners and safety.

ETHICS AND DISSEMINATION

This systematic review will evaluate the efficacy and safety of PDE5 inhibitors on DMED. This review does not require ethical approval and will be reported in a peer-reviewed journal.

TRIAL REGISTRATION NUMBER

PROSPERO CRD42018095185.

Aging and sexual health: getting to the problem

Erectile dysfunction (ED) is one of the most common disorders in male and is often associated with other age-related comorbidities. The aging process affects the structural organization and function of penile erectile components such as smooth muscle cell and vascular architecture. These modifications affect penile hemodynamics by impairing cavernosal smooth muscle cell relaxation, reducing penile elasticity, compliance and promoting fibrosis. This review aims to identify the mechanisms of ED in the penile aging process in experimental and clinical data. It also highlights areas that are in need of more research. The search strategies yielded total records screened from PubMed. Clarification of the molecular mechanisms that accompanies corpus cavernosum aging and aging-associated ED will aid new perspectives in the development of novel mechanism-based therapeutic approaches. Age is not a limiting factor for ED medical management, and it is never too late to treat. Hypogonadism should be managed regardless of age, and synergistic effects have been found during testosterone (T) replacement therapy when used along with oral phosphodiesterase-5 (PDE-5) inhibitors. Therefore, the clinical management of ED related to aging can be done by therapeutic interventions that include PDE-5 inhibitors, and other pharmacological treatments.

Emerging drugs for the treatment of erectile dysfunction

INTRODUCTION

Erectile dysfunction adversely affects the lives of millions of men, and is the most commonly treated sexual disorder today. The erectile process has been extensively investigated, with major advances made in elucidating many of the complex molecular pathways involved. These advances have allowed researchers to design and study drug formulations that target various aspects of this complex process. The initial culmination of this research was the introduction of phosphodiesterase 5-inhibitors. While effective in many patients, they are not satisfactory for all afflicted men. As a result, researchers are developing novel drugs that target different molecular pathways.

AREAS COVERED

The paper will review these pathways, and the potential agents that target them. More specifically, first dopaminergic and melanocortin receptor agonists that act centrally will be covered. Then, the paper will examine the "second-generation" phosphodiesterase 5-inhibitors, soluble guanylate cyclases, rho-kinase inhibitors, and maxi-k channel activators that act peripherally.

EXPERT OPINION

Most of these novel drugs have yet to reach Phase III studies. However, it is likely that in years to come, patients will be selectively treated with these novel agents as a monotherapy or in combination with others acting in a synergistic manner.

Current Diagnosis and Management of Erectile Dysfunction

Erectile dysfunction (ED) affects a growing number of men in the USA and abroad, with significant impacts on sexual function and overall quality of life. The risk factors for ED are numerous and include a strong link to cardiovascular disease, such that men with ED should be screened for cardiovascular disease. The evaluation of men presenting with ED includes a comprehensive history and physical exam to aid in the identification of comorbidities as well as laboratory testing to evaluate hormone and lipid levels and sugar metabolism. Adjunct studies are also available, though their utility is often limited to specific subtypes of ED. Once the etiology of ED is established, treatment can be initiated using appropriate medical therapies, including phosphodiesterase type 5 (PDE5) inhibitors, and transurethral or intracavernosal therapies, with surgical intervention via revascularization or penile prosthesis placement in men demonstrating a lack of response to medical therapy. In all cases of ED, a psychogenic component is present and referral for psychological intervention with or without medical therapy should be considered.

Udenafil for the treatment of erectile dysfunction

Erectile dysfunction (ED) is often perceived by both patients and sexual partners as a serious problem that can jeopardize quality of life, psychosocial or emotional well-being, and the partnership in the long term. Since their introduction, oral phosphodiesterase type 5 inhibitors (PDE5Is) have been found to be highly effective and well tolerated, and are available as the first-line therapy for the treatment of ED. Udenafil is one of the selective PDE5Is made available in recent years for the treatment of ED. Udenafil has clinical properties of both relatively rapid onset and long duration of action due to its pharmacokinetic profile, thereby providing an additional treatment option for ED men to better suit individual needs. There is positive evidence that udenafil is effective and well tolerated in the treatment of ED of a broad spectrum of etiologies or severity. Udenafil is as effective in the treatment of diabetes mellitus-associated ED as other PDE5Is. Due to the clinical property of relatively long duration of action, udenafil may be another option in daily dosing treatment for ED, as suggested by its favorable efficacy and safety profile. Most adverse effects reported from clinical trials are mild or moderate in severity, without any serious adverse event, with headache and flushing being the most common. Also, the concomitant use of anti-hypertensive drugs or alpha-1-blockers does not significantly affect the efficacy and safety profile of udenafil. However, additional studies with larger cohorts including prospective, multicenter, comparative studies with patients of different ethnicities are needed to further validate the favorable findings of udenafil in the treatment of ED.

SOP conservative (medical and mechanical) treatment of erectile dysfunction

INTRODUCTION

Erectile dysfunction (ED) is the most frequently treated male sexual dysfunction worldwide. ED is a chronic condition that exerts a negative impact on male self-esteem and nearly all life domains including interpersonal, family, and business relationships.

AIM

The aim of this study is to provide an updated overview on currently used and available conservative treatment options for ED with a special focus on their efficacy, tolerability, safety, merits, and limitations including the role of combination therapies for monotherapy failures.

METHODS

The methods used were PubMed and MEDLINE searches using the following keywords: ED, phosphodiesterase type 5 (PDE5) inhibitors, oral drug therapy, intracavernosal injection therapy, transurethral therapy, topical therapy, and vacuum-erection therapy/constriction devices. Additionally, expert opinions by the authors of this article are included.

RESULTS

Level 1 evidence exists that changes in sedentary lifestyle with weight loss and optimal treatment of concomitant diseases/risk factors (e.g., diabetes, hypertension, and dyslipidemia) can either improve ED or add to the efficacy of ED-specific therapies, e.g., PDE5 inhibitors. Level 1 evidence also exists that treatment of hypogonadism with total testosterone < 300 ng/dL (10.4 nmol/L) can either improve ED or add to the efficacy of PDE5 inhibitors. There is level 1 evidence regarding the efficacy and safety of the following monotherapies in a spectrum-wide range of ED populations: PDE5 inhibitors, intracavernosal injection therapy with prostaglandin E1 (PGE1, synonymous alprostadil) or vasoactive intestinal peptide (VIP)/phentolamine, and transurethral PGE1 therapy. There is level 2 evidence regarding the efficacy and safety of the following ED treatments: vacuum-erection therapy in a wide range of ED populations, oral L-arginine (3-5 g), topical PGE1 in special ED populations, intracavernosal injection therapy with papaverine/phentolamine (bimix), or papaverine/phentolamine/PGE1 (trimix) combination mixtures. There is level 3 evidence regarding the efficacy and safety of oral yohimbine in nonorganic ED. There is level 3 evidence that combination therapies of PDE5 inhibitors + either transurethral or intracavernosal injection therapy generate better efficacy rates than either monotherapy alone. There is level 4 evidence showing enhanced efficacy with the combination of vacuum-erection therapy + either PDE5 inhibitor or transurethral PGE1 or intracavernosal injection therapy. There is level 5 evidence (expert opinion) that combination therapy of PDE5 inhibitors + L-arginine or daily dosing of tadalafil + short-acting PDE5 inhibitors pro re nata may rescue PDE5 inhibitor monotherapy failures. There is level 5 evidence (expert opinion) that adding either PDE5 inhibitors or transurethral PGE1 may improve outcome of penile prosthetic surgery regarding soft (cold) glans syndrome. There is level 5 evidence (expert opinion) that the combination of PDE5 inhibitors and dapoxetine is effective and safe in patients suffering from both ED and premature ejaculation.

A 6 month, prospective, observational study of PDE5 inhibitor treatment persistence and adherence in Latin American men with erectile dysfunction

OBJECTIVES

To assess persistence/adherence rates of phosphodiesterase type-5 inhibitor (PDE5I) on-demand dosing in Latin American men with erectile dysfunction (ED), and explore patient characteristics and treatment factors that may be predictive for PDE5I persistence and adherence.

METHODS

Men from Brazil, Mexico, and Venezuela with ED who were naïve to PDE5Is were prescribed sildenafil, tadalafil, vardenafil, or lodenafil on-demand dosing and asked to provide information about PDE5I use at baseline and at 1, 3, and 6 months. Patients were persistent if they used ≥1 dose during the 4 week period prior to each evaluation. Patients were adherent if they complied with dosing instructions during most recent dose. Main outcome measures included Persistence and Adherence Questionnaire (PAQ), Partner Relationship Questionnaire (PRQ), Self-Esteem and Relationship (SEAR) Questionnaire, and International Index of Erectile Function (IIEF). Multivariate logistic regression was used to identify factors associated with persistence and adherence.

RESULTS

A total of 511 men were enrolled; most had mild to moderate ED (77.1%); 317 patients (62.0%) were prescribed tadalafil, 116 (22.7%) sildenafil, 75 (14.7%) vardenafil, and 3 (0.6%) lodenafil (not further analyzed). A total of 340 patients (66.5%) were 'persistent' at 6 months; 345 (67.5%) were 'adherent'. Persistence and adherence were associated with age, education level, and ED duration. Reasons for non-persistence included medication cost and lack of efficacy. Study limitations included its design, brief observation period, its bias observed toward tadalafil selection; its dependence on patient self-reporting, limited number of factors that were analyzed for persistence/adherence association, its small number of participating patients and Latin American countries, and inherent differences in PDE5I preference and medical practices.

CONCLUSION

Approximately two-thirds of PDE5I-naïve, Latin American men with ED were persistent and adherent after 6 months of therapy. Factors like education level, ED severity, and ED duration were associated with persistence and adherence; additional study is warranted to investigate the predictive value of these factors.

A review of analytical methods for the determination of four new phosphodiesterase type 5 inhibitors in biological samples and pharmaceutical preparations

The introduction of oral phosphodiesterase type 5 inhibitor therapy in 1998 revolutionized the treatment of erectile dysfunction. Erectile dysfunction is the most common sexual problem in men. It often has a profound effect on intimate relationships and quality of life. The analysis of pharmaceuticals is an important part of the drug development process as well as for routine analysis and quality control of commercial formulations. Whereas the determination of sildenafil citrate, vardenafil and tadalafil are well documented by a variety of methods, there are few publications about the determination of udenafil, lodenafil carbonate, mirodenafil and avanafil. The paper presents a brief review of the action mechanism, adverse effects, pharmacokinetics and the most recent analytical methods that can determine drug concentration in biological matrices and pharmaceutical formulations of these four drugs.

Adjunctive treatment with lodenafil carbonate for erectile dysfunction in outpatients with schizophrenia and spectrum: a randomized, double-blind, crossover, placebo-controlled trial

INTRODUCTION.: Evidence is accumulating to support the presence of erectile dysfunction in patients with schizophrenia. This dysregulation may be amenable to therapeutic intervention to improve adherence and quality of life of patients who suffer from schizophrenia and schizoaffective disorders. AIM.: We aimed to evaluate the use of adjunctive medication lodenafil for the treatment of erectile dysfunction in outpatients with schizophrenia and spectrum. METHODS.: The design was a randomized, double-blind, crossover, placebo-controlled trial with lodenafil and it was carried at the Schizophrenia Outpatients Program. MAIN OUTCOME MEASURES.: The measures used to assess sexual dysfunction were Arizona Sexual Experiences Scale (ASEX) and International Index of Erectile Function (IIEF). The Positive and Negative Syndrome Scale (PANSS) and the Quality of Life Scale (QLS) were also used. The measures included the levels of prolactin, estradiol, luteinizing hormone, sex hormone-binding globulin, free testosterone, and total testosterone at baseline and end point. Lodenafil and placebo pills were used by the patients for 16 weeks. RESULTS.: Fifty male outpatients fulfilled the criteria and 94% of the participants completed the study. Lodenafil and placebo produced improvement in ASEX, IIEF scale, PANSS, and QLS, and there was no statistical difference between lodenafil and placebo groups in all sexual domains in the results of PANSS and QLS and in the results of hormone levels. CONCLUSION.: These results indicate that both lodenafil and placebo were effective in the treatment of erectile dysfunction for schizophrenia. Placebo effect is very important in patients with schizophrenia and this study showed the importance of discussing sexuality and trying to treat these patients. Further studies designed to test treatments of erectile dysfunction in patients who suffer from schizophrenia are necessary.

Mechanisms of penile erection and basis for pharmacological treatment of erectile dysfunction

Erection is basically a spinal reflex that can be initiated by recruitment of penile afferents, both autonomic and somatic, and supraspinal influences from visual, olfactory, and imaginary stimuli. Several central transmitters are involved in the erectile control. Dopamine, acetylcholine, nitric oxide (NO), and peptides, such as oxytocin and adrenocorticotropin/α-melanocyte-stimulating hormone, have a facilitatory role, whereas serotonin may be either facilitatory or inhibitory, and enkephalins are inhibitory. The balance between contractant and relaxant factors controls the degree of contraction of the smooth muscle of the corpora cavernosa (CC) and determines the functional state of the penis. Noradrenaline contracts both CC and penile vessels via stimulation of α₁-adrenoceptors. Neurogenic NO is considered the most important factor for relaxation of penile vessels and CC. The role of other mediators, released from nerves or endothelium, has not been definitely established. Erectile dysfunction (ED), defined as the "inability to achieve or maintain an erection adequate for sexual satisfaction," may have multiple causes and can be classified as psychogenic, vasculogenic or organic, neurologic, and endocrinologic. Many patients with ED respond well to the pharmacological treatments that are currently available, but there are still groups of patients in whom the response is unsatisfactory. The drugs used are able to substitute, partially or completely, the malfunctioning endogenous mechanisms that control penile erection. Most drugs have a direct action on penile tissue facilitating penile smooth muscle relaxation, including oral phosphodiesterase inhibitors and intracavernosal injections of prostaglandin E₁. Irrespective of the underlying cause, these drugs are effective in the majority of cases. Drugs with a central site of action have so far not been very successful. There is a need for therapeutic alternatives. This requires identification of new therapeutic targets and design of new approaches. Research in the field is expanding, and several promising new targets for future drugs have been identified.

Erectile dysfunction after radical prostatectomy: treatment options

Erectile dysfunction is a common problem after radical prostatectomy, with almost all men experiencing this complication for at least a short period after such surgery. There is evidence that early use of phosphodiesterase type 5 inhibitors, intracavernous vasoactive drugs, intraurethral alprostadil or vacuum devices can improve the recovery of postoperative erectile function. The same therapeutic modalities can be used to treat erectile dysfunction after radical prostatectomy. Physicians must be active and counsel patients and partners to improve adherence to penile rehabilitation or erectile dysfunction treatment.

The future is today: emerging drugs for the treatment of erectile dysfunction

IMPORTANCE OF THE FIELD

Erectile dysfunction (ED) is the most common male sexual dysfunction presented for treatment affecting between 10 and 20% of men. PDE type 5 inhibitors (PDE5I) now account for the largest segment of the ED market. While these drugs are highly efficacious for many men, a relatively large subset of ED patients who do not respond to PDE5I is increasingly recognized.

AREAS COVERED IN THIS REVIEW

In this review, we discuss clinical and preclinical evidence supporting various emerging compounds that regulate penile erection both centrally (clavulanic acid, dopamine and melanocortin receptor agonists) and peripherally (novel PDE5I, soluble and particulate guanylil cyclase activators, rho-kinase inhibitors and maxi-K channel openers).

WHAT THE READER WILL GAIN

The reader will gain a broad understanding of erectile (patho-)physiology and gain insights in the mechanisms of action, efficacy and adverse events of various compounds under development for the treatment of ED.

TAKE HOME MESSAGE

We expect emerging drugs to allow treatment protocols tailored to the specific needs of each individual patient, taking into consideration the efficacy of erectile performance enhancement and the potential for adverse events. This tailored approach may include combination of various emerging drugs to enhance efficacy in difficult-to-treat patients.