The treatment of erectile dysfunction in patients with neurogenic disease

Erectile dysfunction (ED) related to compromise of the nervous system is an increasingly common occurrence. This may be due to the multifactorial nature of ED, the myriad of disorders affecting the neurotransmission of erectogenic signals, and improved awareness and diagnosis of ED. Nevertheless, neurogenic ED remains poorly understood and characterized. Disease related factors such as depression, decreased physical and mental function, the burden of chronic illness, and loss of independence may preclude sexual intimacy and lead to ED as well. The amount of data regarding treatment options in subpopulations of differing neurologic disorders remains scarce except for men with spinal cord injury. The treatment options including phosphodiesterase inhibitors, intracavernosal or intraurethral vasoactive agents, vacuum erection devices (VED) and penile prosthetic implantation remain constant. This review discusses the options in specific neurologic conditions, and briefly provides insight into new and future developments that may reshape the management of neurogenic ED.

A review of the efficacy and safety of mirodenafil in the management of erectile dysfunction

Erectile dysfunction (ED) is a common disorder that can jeopardize quality of life and the partnership of patients and their sexual partners. The advent of oral phosphodiesterase type 5 inhibitors (PDE5Is) has revolutionized a treatment for ED, and they are recognized as the first-line therapy for ED, regardless of its etiology. Mirodenafil, a second-generation PDE5I, has biochemical profiles such as high affinity for PDE5 and high selectivity for PDE5 over other PDE isoforms, compared to other existing PDE5Is such as sildenafil, vardenafil and tadalafil. Available evidence has suggested that doses of 50 and 100 mg mirodenafil effectively improve ED [with improvements in the erectile function domain of the International Index of Erectile Function (IIEF-EF) scores, positive responses to questions 2 of the Sexual Encounter Profiles (SEP2) and questions 3 of the Sexual Encounter Profiles (SEP3): 7.6-11.6 points, 27.72-38.98% and 44.20-67.33%, respectively] in a broad range of patient populations with ED of a variety of underlying etiologies, severities and ages, without any serious treatment-related adverse effects. In the treatment of diabetic ED, a traditionally difficult-to-treat population, 100 mg mirodenafil has been reported to offer favorable efficacy (with improvements in the IIEF-EF scores, and positive responses to the SEP2 and the SEP3: 9.3 points, 36.1% and 61.8%, respectively) and tolerability (mild adverse effects of less than 19.6%), which are comparable with results from clinical studies on other PDE5Is. Mirodenafil appears to be effective, safe and well tolerated in men with both ED and hypertension or lower urinary tract symptoms (LUTS)/benign prostatic hyperplasia (BPH) who are taking concomitant antihypertensive medications or α1-blockers. Furthermore, recent evidence has indicated that mirodenafil may be a potential option for chronic dosing in the treatment of ED despite its short half-life (T 1/2). Most of the available clinical studies have reported that adverse effects (up to 53.7%) caused by 50 and 100 mg mirodenafil are mild or moderate in severity, with headache (1.8-14.8%) and flushing (6.7-24.1%) being the most common. Due to the pharmacodynamic profiles of mirodenafil, its tolerability is expected to be somewhat better than those of the other PDE5Is. However, further well designed studies with larger cohorts of different ethnicities, flexible dosing schedules and long-term follow up are necessary to confirm the favorable efficacy and tolerability profiles of mirodenafil for the treatment of ED.

Phosphodiesterase Type 5 Inhibitor and Erectile Dysfunction in Lower Urinary Tract Symptoms

Benign prostatic hyperplasia (BPH) is one of the most common diseases in older men and mostly induces lower urinary tract symptoms (LUTS). Multiple studies have shown that BPH inducing LUTS are intensely correlated with erectile dysfunction (ED) and that severity of LUTS was proportional to ED severity. Although a direct causal relationship has not been clarified, a tentative pathophysiology has been suggested to interpret the relationship between two disorders. Androgen plays an important role in the maintenance of the functional and structural integrity of the lower urinary tract and penis. Low testosterone, especially free testosterone, worsened detrusor overactivity and replacement of testosterone improved LUTS in the hypogonadal BPH patients. Nitric oxide synthase and nitric oxide are decreased in the transition zone of the hyperplastic prostate but phosphodiesterase types 4, 5, 11 are prominent in transition zone of hyperplastic prostate. Phosphodiesterase type 5 (PDE5) inhibitor with a long half-life could obtain the desired effect; therefore, tadalafil and undenafil frequently have been used to evaluate the effects in the two disorders. In clinical trials, tadalafil showed improvement of BPH-induced LUTS, but few of the studies showed a significant improvement on uroflowmetry. PDE5 inhibitors increase the concentration of cyclic guanosine monophosphate (cGMP) in plasma and smooth muscle, promoting erection of the penis, as well as relaxation of the bladder neck and prostate, leading to natural voiding. Sexual function and LUTS should be assessed and discussed with the patient when choosing the appropriate strategy and the patient's response to treatment should also be evaluated at the same time.

Impact of cardiovascular risk factors and related comorbid conditions and medical therapy reported at baseline on the treatment response to tadalafil 5 mg once-daily in men with lower urinary tract symptoms associated with benign prostatic hyperplasia: an integrated analysis of four randomised, double-blind, placebo-controlled, clinical trials

PURPOSE

The influence of cardiovascular risk factors/comorbidities on response to oral once-daily tadalafil 5 mg was explored in men with lower urinary tract symptoms associated with benign prostatic hyperplasia (LUTS/BPH).

METHODS

This post hoc analysis pooled data from four double-blind studies in which 1498 men with > 6-mo history of LUTS/BPH were randomised and received either once-daily placebo (n = 746) or tadalafil 5 mg (n = 752) for 12 weeks. Descriptive statistics were reported for changes in total International Prostate Symptom Score (IPSS), IPSS voiding and storage subscores, and IPSS quality-of-life (QoL) index. Treatment group differences by baseline clinical and cardiovascular factors and medical therapies were examined using analysis of covariance.

RESULTS

Tadalafil was effective in men with LUTS/BPH and cardiovascular risk factors/comorbidities except for patients receiving > 1 antihypertensive medication. Placebo-adjusted least squares (LS) mean improvements in total IPSS were -1.2 (95% CI: -2.5 to -0.0) in men taking > 1 antihypertensive medication vs. -3.3 (95% CI: -4.4 to -2.1) in men taking one medication (interaction p = 0.020). In addition, placebo-adjusted LS mean improvements in total IPSS were -0.2 (95% CI, -2.1 to 1.7) in men who reported use of diuretics vs. -2.8 (95% CI, -3.7 to -1.9) in men who reported taking other antihypertensive medications vs. -2.3 (95% CI, -3.2 to -1.5) in men who reported not using any antihypertensive drug (p-value for interaction = 0.053).

CONCLUSIONS

Once-daily tadalafil 5 mg improved LUTS/BPH, regardless of severity, in men with coexisting cardiovascular risk factors/comorbidities, except for patients with history of > 1 drug for arterial hypertension. Use of diuretics may contribute to patients' perception of a negated efficacy of tadalafil on LUTS/BPH. Comorbidities should be considered when choosing the optimal medicine to treat men with LUTS/BPH.

Total Syntheses of Aporphine Alkaloids via Benzyne Chemistry: An Approach to the Formation of Aporphine Cores

Total syntheses of lysicamine, (±)-nuciferine, (±)-nornuciferine, (±)-zanthoxyphylline iodide, (±)-O-methylisothebaine, and (±)-trimethoxynoraporphine were accomplished by an approach that involves the formation of aporphine cores through reactions between an isoquinoline derivative and silylaryl triflates promoted by CsF. Unprecedented formations of aporphine cores proceeded in good yields presumably through [4 + 2] cycloaddition reactions followed by hydrogen migrations.

Results from an online survey investigating ED patients' insights and treatment expectations

Data suggest that the currently available therapies for erectile dysfunction (ED) do not meet all the patients' and their partners' expectations. The aim was to assess ED patients' treatment expectations for a variety of sex- and drug-related aspects such as importance of spontaneity, partner satisfaction, ideal onset of action and ideal duration of action. A total of n=1124 men with ED and n=410 healthy men, aged 30-75, participated in this online survey. The ED sample was further divided into patients currently undergoing treatment (CTG), patients who had been undergoing treatment in the past (PTG) and naïve patients (NG). The International Index of Erectile Function as well as a mix of study-specific questions was used. All groups considered 'maintaining an erection until the partner reaches orgasm' the most important aspect regarding erectile function. 'Being able to please the partner' was considered as the most important aspect for a fulfilled sex life. The majority of men (38.1%) further considered an onset of action of about 15 min to be desirable. In all, 95.9% further considered a duration of action up to 4 h to be desirable whereas approximately 71% of men considered a duration of more than 12 h to be too long. It seems that once the basic functional aspects related to erectile function have been covered, additional benefits such as 'spontaneity' and 'pleasing the partner' become important and may be critical for choosing the optimum individual treatment, to improve the sexual satisfaction and the adherence to the treatment.

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.

An open-label, multicenter, randomized, crossover study comparing sildenafil citrate and tadalafil for treating erectile dysfunction in Chinese men naïve to phosphodiesterase 5 inhibitor therapy

The study was to compare treatment preference, efficacy, and tolerability of sildenafil citrate (sildenafil) and tadalafil for treating erectile dysfunction (ED) in Chinese men naοve to phosphodiesterase 5 (PDE5) inhibitor therapies. This multicenter, randomized, open-label, crossover study evaluated whether Chinese men with ED preferred 20-mg tadalafil or 100-mg sildenafil. After a 4 weeks baseline assessment, 383 eligible patients were randomized to sequential 20-mg tadalafil per 100-mg sildenafil or vice versa for 8 weeks respectively and then chose which treatment they preferred to take during the 8 weeks extension. Primary efficacy was measured by Question 1 of the PDE5 Inhibitor Treatment Preference Questionnaire (PITPQ). Secondary efficacy was analyzed by PITPQ Question 2, the International Index of Erectile Function (IIEF) erectile function (EF) domain, sexual encounter profile (SEP) Questions 2 and 3, and the Drug Attributes Questionnaire. Three hundred and fifty men (91%) completed the randomized treatment phase. Two hundred and forty-two per 350 (69.1%) patients preferred 20-mg tadalafil, and 108/350 (30.9%) preferred 100-mg sildenafil (P < 0.001) as their treatment in the 8 weeks extension. Ninety-two per 242 (38%) patients strongly preferred tadalafil and 37/108 (34.3%) strongly the preferred sildenafil. The SEP2 (penetration), SEP3 (successful intercourse), and IIEF-EF domain scores were improved in both tadalafil and sildenafil treatment groups. For patients who preferred tadalafil, getting an erection long after taking the medication was the most reported reason for tadalafil preference. The only treatment-emergent adverse event reported by > 2% of men was headache. After tadalafil and sildenafil treatments, more Chinese men with ED naοve to PDE5 inhibitor preferred tadalafil. Both sildenafil and tadalafil treatments were effective and safe.

Effects of three-times-per-week versus on-demand tadalafil treatment on erectile function and continence recovery following bilateral nerve sparing radical prostatectomy: results of a prospective, randomized, and single-center study

Erectile dysfunction (ED) and urinary incontinence after bilateral nerve-sparing radical prostatectomy (BNSRP) still remain major causes of morbidity. Phosphodiesterase type 5 inhibitors (PDE5-Is) have a role in the treatment of ED after BNSRP. Several studies in patients with ED and lower urinary tract symptoms demonstrated that PDE5-Is could improve both erectile function and urinary symptoms. The aim of this study was to compare the efficacies of two dosing regimens of 20 mg tadalafil (on-demand and 3 times per week) and to assess the role of tadalafil in recovery of erectile function and continence after BNSRP. We conducted a single-center, prospective, randomized controlled trial of three times per week versus on-demand tadalafil 20 mg and a control group after BNSRP. A total of 129 preoperatively potent and continent patients were included in the study. The patients were evaluated at 6 weeks and 12 months postoperatively for erectile function and continence status. There was no significant difference between all three groups with respect to erectile function at 6 weeks after the surgery. Twelve months after the surgery, the International Index of Erectile Function score was significantly higher in the group using tadalafil 20 mg three times per week. However, there was no significant difference between the treated groups and the control group with respect to the continence status at 12 months after the surgery. There was no correlation between incontinence and ED after the surgery in all groups. Tadalafil 20 mg three times per week is an efficacious and well-tolerated treatment option for ED after BNSRP. Treatment with 20 mg tadalafil either three times per week or on demand cannot improve continence recovery after BNSRP compared with the control group.

Effect of the novel BKCa channel opener LDD175 on the modulation of corporal smooth muscle tone

INTRODUCTION

The BKCa channel has been reported to play an important role in erectile function. Recently, novel BKCa channel activator, LDD175, was introduced.

AIM

This study aims to investigate whether LDD175 relaxes corporal smooth muscle (CSM) via BKCa channel activation.

METHODS

After isolation of CSM strip from a male rabbit model, contraction studies using organ bath was performed. Isolating human tissue and cell cultures, electrophysiological studies were done via whole-cell patch-clamp recording.

MAIN OUTCOME MEASURES

Vasodilatory effects of LDD175 were evaluated by cumulative addition ranging from 10(-7) to 10(-4) M in corpus cavernosal strips after precontraction with 10(-5) M phenylephrine via organ bath system. Using cultured human CSM cells, patch-clamp recording was performed. Erectile function was measured by in vivo rat cavernous nerve stimulation.

RESULTS

LDD175 caused an endothelium-independent relaxation of corporal tissues, and this effect was abolished by pretreatment with iberiotoxin. The relaxation effect of 10(-4) M LDD175 was greater than that of 10(-6) M udenafil (54.0 ± 3.1% vs. 34.5 ± 3.9%, P < 0.05); 10(-5) M LDD175 with 10(-6) M udenafil caused a greater relaxation effect on strips than 10(-5) M LDD175 or 10(-6) M udenafil alone (50.7%, 34.1%, vs. 20.7%, respectively, P < 0.001). In patch-clamp recordings, LDD175 increased K(+) currents in a dose-dependent manner, and washout of LDD175 or the addition of iberiotoxin fully reversed the increase. Intravenous LDD175 improved erectile function measured by area under the curve (AUC) of the intracavernosal pressure (ICP)/arterial blood pressure (ABP) ratio (1,612.1 ± 135.6 vs. 1,093.7 ± 123.1, P < 0.05). There was no difference between 10 mg/kg LDD175 and 1 mg/kg udenafil regarding maximal ICP, maximal ICP/ABP ratio, and the AUC of the ICP/ABP ratio (P > 0.05).

CONCLUSIONS

LDD175 leads to an endothelium-independent relaxation of erectile tissue, primarily through the opening of BKCa channels. The results suggest that LDD175 might be a new candidate treatment for erectile dysfunction.

Adherence to phosphodiesterase type 5 inhibitors in the treatment of erectile dysfunction in long-term users: how do men use the inhibitors?

Introduction

The high effectiveness of phosphodiesterase type 5 inhibitors (PDE5-i) in the treatment of erectile dysfunction (ED) has been demonstrated. However, previous research shows that PDE5-i treatments have high discontinuation rates.

Aim

The main goals of this study were to (i) characterize the way men use PDE5-i and (ii) analyze the adherence to treatment, identifying the factors that influence PDE5-i use.

Methods

A total of 148 men with clinical diagnosis for ED who maintained the treatment with PDE5-i for over 3 years were interviewed. Interviews concerning their ongoing treatment were carried out using a standardized questionnaire with quantitative and qualitative items.

Main Outcome Measures

Physiological measures included the intracavernous alprostadil injection test, associated with penile rigidometry and penile Doppler ultrasound. The qualitative measure included two questions: “Do you use the drug in every sexual intercourse?” and “How do you use the inhibitor?”

Results

ED causes were classified as venogenic (31%), arteriogenic (23%), psychogenic (18%), iatrogenic (13%), neurogenic (8%), and diabetic (7%). Participation rate was 71.8%. Of the 148 patients studied, 75% claimed not to use PDE5-i in every intercourse. Most used tadalafil (66%), followed by sildenafil (20%), vardenafil (10%), and 4% alternated the type of medicine. Four main categories emerged concerning the factors that determine the intake of PDE5-i in some intercourse situations and not in others: (i) psychological factors; (ii) medication-related factors; (iii) circumstantial factors; and (iv) relational factors.

Conclusion

The analysis of men's narratives revealed a combination of factors that influence the adherence to PDE5-i. The psychological and medication-related factors were the most prevalent. This study highlighted the importance of taking these factors into account, both at the time of prescription and during the follow-up in order to improve adherence. Carvalheira A, Forjaz V, and Pereira NM. Adherence to phosphodiesterase type 5 inhibitors in the treatment of erectile dysfunction in long-term users: How do men use the inhibitors? Sex Med 2014;2:96–102.

Extracorporeal shockwave therapy in the treatment of erectile dysfunction: a prospective, randomized, double-blinded, placebo controlled study

OBJECTIVES

To investigate the role of low-intensity extracorporeal shockwave therapy in the treatment of erectile dysfunction.

METHODS

This was a double-blinded, single-center, prospective, randomized, placebo-controlled trial. After a 2-week phosphodiesterase type 5 inhibitor washout period, patients were assessed with Sexual Health Inventory for Men, International Index of Erectile Function-ED domain scores and Erection Hardness Score. Randomization into either the low-intensity extracorporeal shockwave therapy group or the sham group took place. After the 9-week treatment period, patients were followed up 4 weeks later. Follow-up assessment was in the form of International Index of Erectile Function-ED domain score and Erection Hardness Score.

RESULTS

A total of 70 patients were recruited into the study, 58 patients completed the study. A total of 28 patients were randomized into the sham therapy arm, and 30 patients were randomized into the low-intensity extracorporeal shockwave therapy arm. There was no significant difference between these two groups in baseline International Index of Erectile Function-ED domain score and Erection Hardness Score. The mean International Index of Erectile Function-ED domain score of the low-intensity extracorporeal shockwave therapy arm and sham arm in week 13 were 17.8 ± 4.8 and 15.8 ± 6.1, respectively (P = 0.156). The mean Erection Hardness Scores in week 13 were 2.7 ± 0.5 and 2.4 ± 0.9, respectively (P = 0.163). When patients were stratified into different baseline Sexual Health Inventory for Men subgroups, the pre-intervention and post-intervention difference in low-intensity extracorporeal shockwave therapy was found to be significant in the subgroup with severe erectile dysfunction (low-intensity extracorporeal shockwave therapy International Index of Erectile Function-ED domain improvement: 10.1 ± 4.1 vs sham therapy International Index of Erectile Function-ED domain improvement: 3.2 ± 3.3; P = 0.003).

CONCLUSION

The present trial shows the tolerability and clinical efficacy of low-intensity extracorporeal shockwave therapy in a subgroup of patients with erectile dysfunction.

Increased expression of TRPC4 channels associated with erectile dysfunction in diabetes

In recent reports, an association between altered TRPC channel function and the development of various diabetic complications has drawn the attention of many investigators. The aim of this study was to investigate the expression of TRPC4 channels of corpus smooth muscle (CSM) cells in diabetes, and to evaluate the association between erectile dysfunction (ED) and altered TRPC4 channel function. The expression of TRPC4 in the penile tissue of human, normal and diabetic rat was investigated using RT-PCR, western blotting and immunohistochemistry (IHC). In vivo gene transfer of dominant negative (DN) TRPC4 into the CSM of rat was conducted. In vivo pelvic nerve stimulation was performed to measure erectile function. Expression of TRPC1, TRPC3, TRPC4 and TRPC6 in human and rat CSM tissues was confirmed by RT-PCR, western blot and IHC. In the diabetic rat, the expression levels of mRNA and protein of the TRPC4, and TRPC6 were significantly increased compared to control rats (p < 0.05). The change in TRPC4 expression in the diabetic rats was higher than those of the other TRPC subunits (p < 0.05). The IHC showed that only TRPC4 expression had a higher intensity in the diabetes compared to normal rats (p < 0.05). Gene transfection with TRPC4(DN) into the diabetic rats restored erectile function to levels similar to that of normal controls. Gene expression of TRPC4(DN) in CSM tissue was confirmed by RT-PCR 2 weeks after transfection. This study demonstrated that TRPC4 channel expression increased in the penile CSM cells of diabetic rats. The down-regulation of TRPC4 with DN form restored erectile function in the diabetic rats. The alteration of TRPC4 channel is one of pathophysiology of ED and could be a target for drug development for ED.

Clinical and molecular genetics of the phosphodiesterases (PDEs)

Cyclic nucleotide phosphodiesterases (PDEs) are enzymes that have the unique function of terminating cyclic nucleotide signaling by catalyzing the hydrolysis of cAMP and GMP. They are critical regulators of the intracellular concentrations of cAMP and cGMP as well as of their signaling pathways and downstream biological effects. PDEs have been exploited pharmacologically for more than half a century, and some of the most successful drugs worldwide today affect PDE function. Recently, mutations in PDE genes have been identified as causative of certain human genetic diseases; even more recently, functional variants of PDE genes have been suggested to play a potential role in predisposition to tumors and/or cancer, especially in cAMP-sensitive tissues. Mouse models have been developed that point to wide developmental effects of PDEs from heart function to reproduction, to tumors, and beyond. This review brings together knowledge from a variety of disciplines (biochemistry and pharmacology, oncology, endocrinology, and reproductive sciences) with emphasis on recent research on PDEs, how PDEs affect cAMP and cGMP signaling in health and disease, and what pharmacological exploitations of PDEs may be useful in modulating cyclic nucleotide signaling in a way that prevents or treats certain human diseases.

Erectile dysfunction in the elderly: an old widespread issue with novel treatment perspectives

Erectile dysfunction (ED) is one of the most common chronic diseases affecting men and its prevalence increases with aging. It is also the most frequently diagnosed sexual dysfunction in the older male population. A number of different diseases potentially worsening sexual function may occur in elderly people, together with polypharmacy. Related causes of ED are variable and can include arterial, neurogenic, hormonal, cavernosal, iatrogenic, and psychogenic causes. The aim of the present review was to examine the main aspects of erectile dysfunction going through epidemiology and pathophysiology and revise most of ED in elderly disabled men and in those affected with psychiatric disorders. Lastly we tried to focus on the main aspects of nonpharmacological and pharmacological treatments of ED and the recreational use in the elderly. Phosphodiesterase-5 inhibitors (PDE5-I) are commonly used for on-demand or chronic treatment of ED. It is widely known that PDE5-I have lower response rates in older men than in younger patients, but they have the advantages of ease of use and excellent safety profile, also in the elderly. The old and new PDE5-I as well as the alternative treatments for ED are extensively discussed.

Vardenafil dihydrochloride

Vardenafil (VAR) is synthetic, highly selective, and potent inhibitor of phosphodiesterase-5 which competitively inhibits cyclic guanosine monophosphate (cGMP) hydrolysis and thus increases cGMP levels. It is clinically approved for treatment of erectile dysfunction in men, including diabetic and postprostatectomy patients. Several methods of VAR synthesis are included in this review. UV spectroscopy of VAR showed a λmax of approximately 270nm, and IR spectroscopy principal peaks were observed at 3420 (NH), 1724 (CO), 1600 (CC, and CN), 1491 (CHCH) cm(-1). Characteristic carbonyl (CO) carbon was observed in nuclear magnetic resonance spectroscopy at 162.44ppm. The molecular mass was observed at m/z=488.9 (molecular weight=488.2) and the fragmentation pattern was studied using ion trap mass spectrometry. In addition, different analytical methods for determination of vardenafil are also described in this profile. Pharmacokinetic properties of VAR have great impact on efficacy. VAR is rapidly absorbed and slowly metabolized, with an absolute bioavailability of 15%. It is extensively metabolized by CYP3A4 into several metabolites, the most pharmacologically active of which is N-desethyl VAR (M1). The elimination half-life of VAR and M1 is about 4-5h. VAR is primarily excreted as metabolites in the feces and to a small extent in urine. VAR is generally well tolerated, with a favorable safety profile and few transient side effects, including headache, flushing, dyspepsia, and rhinitis.

Pharmacologic therapy for erectile dysfunction and its interaction with the cardiovascular system

Phosphodiesterase (PDE) enzymes are widely distributed throughout the body, having numerous effects and functions. The PDE type 5 (PDE5) inhibitors are widely used to treat erectile dysfunction (ED). Recent, intense preclinical and clinical research with PDE5 inhibitors has shed light on new mechanisms and has revealed a number of pleiotropic effects on the cardiovascular (CV) system. To date, PDE5 inhibition has been shown to be effective for the treatment of idiopathic pulmonary arterial hypertension, and both sildenafil and tadalafil are approved for this indication. However, current or future PDE5 inhibitors have the potential of becoming clinically useful in a variety of CV conditions such as heart failure, coronary artery disease, and hypertension. The present review discusses recent findings regarding pharmacologic treatment of ED and its interaction with the CV system and highlights current and future clinical applications beyond ED.

Pathophysiological role of the renin-angiotensin system on erectile dysfunction

BACKGROUND

The renin-angiotensin system (RAS) has been shown to play an active role within the erectile tissues. The aim of this narrative review is to summarize the literature addressing the pathophysiological role of RAS on erectile function. Additionally, we update evidence on recent findings on the role of the Ang-(1-7) and Mas receptor on the erectile function and its therapeutic potential for treating erectile dysfunction (ED).

MATERIALS AND METHODS

This narrative review is based on the material searched and obtained via MEDLINE and PubMed up to November 2012. The search terms we used are 'angiotensin, erectile dysfunction, renin, Mas receptor' in combination with 'pathophysiology, fibrosis, pathways'.

RESULTS

The levels of angiotensin (Ang) II, the main component of this system, are increased in the corpus cavernosum as compared to those found in the systemic circulation. Moreover, emerging evidence indicates that an increased activity of Ang II via AT1 receptor might contribute to the development of ED, whereas the pharmacological blockage of Ang II/AT1 actions has beneficial effects on the erection. On the other hand, the heptapeptide Ang-(1-7), known as a major endogenous counter-regulator of Ang II actions, favours penile erection via the activation of Mas receptor.

CONCLUSIONS

Ang-(1-7) and Mas receptor pathway might be considered as a promising therapeutic target for 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.

Herb-drug interaction of Epimedium sagittatum (Sieb. et Zucc.) maxim extract on the pharmacokinetics of sildenafil in rats

Epimedium sagittatum (Sieb. et Zucc.) Maxim is one of the herbs used to treat erectile dysfunction in Traditional Chinese Medicine. Sildenafil is a phosphodiesterase 5 inhibitor used to treat erectile dysfunction in Western Medicine. This study evaluates the herbal-drug interaction of Epimedium sagittatum extract on the pharmacokinetics of sildenafil in rats by ultra-performance liquid chromatography. The rat plasma was sampled from each anesthetized rat after pretreatment with 3-days Epimedium sagittatum extract (1/2 g/kg/day) and intravenous injection with sildenafil (10/30 mg/kg). The pharmacokinetic data demonstrate that the area under the concentration-time curve (AUC) of sildenafil (10 mg/kg) was significantly decreased in groups that received a high dose of Epimedium sagittatum extract. In conclusion, the study demonstrates that there was significant herb-drug interaction of Epimedium sagittatum extract on the pharmacokinetics of sildenafil at low and high daily doses, suggesting co-administration use of Epimedium sagittatum extract and sildenafil in clinical practice should be prevented due to possible herb-drug interactions.

PDE5-Is for the Treatment of Concomitant ED and LUTS/BPH

Epidemiologic data in adult men exhibit a strong relationship between erectile dysfunction (ED) and lower urinary tract symptoms suggestive of benign prostatic hyperplasia (LUTS/BPH), indicating that men affected by ED should also be investigated for LUTS/BPH and those presenting with storage or voiding LUTS should be investigated for co-morbid ED. Common pathophysiolgical mechanisms underlying both LUTS/BPH and ED, including alteration of NO/cGMP or RhoA/Rho-kinase signaling and/or vascular or neurogenic dysfunction, are potential targets for proposed phosphodiesterase type 5 inhibitors (PDE5-Is). Several randomized controlled trials and only a few reviews including all commercially available PDE5-Is demonstrated the safety and efficacy of these drugs in the improvement of erectile function and urinary symptoms, in patients affected either by ED, LUTS, or both conditions.

An open-label, long-term evaluation of the safety, efficacy and tolerability of avanafil in male patients with mild to severe erectile dysfunction

AIM

Determine the long-term efficacy, safety and tolerability of avanafil, a highly specific, rapidly absorbed phosphodiesterase type 5 inhibitor in male patients with mild to severe erectile dysfunction (ED), with or without diabetes.

METHODS

This was a 52-week, open-label extension of two 12-week, randomised, placebo-controlled, phase 3 trials. Patients were assigned to avanafil 100 mg, but could request 200 mg (for increased efficacy; '100/200-mg' group) or 50 mg (for improved tolerability). Primary end points included percentage of sexual attempts ending in successful vaginal penetration [Sexual Encounter Profile 2 (SEP2)] and intercourse (SEP3) and erectile function domain score per the International Index of Erectile Function (IIEF-EF).

RESULTS

Some 712 patients enrolled; 686 were included in the intent to treat population and contributed to the data. All primary end points showed sustained improvement. SEP2 and SEP3 success rates improved from 44% to 83% and from 13% to 68% (100-mg group) and from 43% to 79% and from 11% to 66% (100/200-mg group), respectively. Mean IIEF-EF domain scores improved from 13.6 to 22.2 (100-mg group) and from 11.9 to 22.7 (100/200-mg group). Avanafil was effective in some patients ≤ 15 min and > 6 h postdose. Sixty-five per cent (112/172) of 'nonresponders' to avanafil 100 mg responded to the 200-mg dose. The most common (≥ 2%) treatment-emergent adverse events were headache, flushing, nasopharyngitis and nasal congestion; < 3% of patients discontinued therapy because of adverse events.

CONCLUSIONS

The long-term tolerability and improvement in sexual function, coupled with rapid onset, suggest that avanafil is well suited for the on-demand treatment of ED.

Avanafil for the treatment of erectile dysfunction: initial data and clinical key properties

Orally active, selective inhibitors of phosphodiesterase type 5 (PDE 5, cyclic GMP PDE), such as sildenafil, tadalafil and vardenafil, are currently the first-choice treatment options for the clinical management of erectile dysfunction (ED) of various etiologies and severities. However, a significant number of patients remain dissatisfied with the available therapies due a lack of efficacy or discomfort arising from adverse events. Several new PDE5 inhibitors, among which are avanafil (TA-1790), lodenafil, mirodenafil, udenafil, SLX-2101, JNJ-10280205 and JNJ-10287069, have recently been approved and introduced into the market or are in the final stages of their clinical development. Avanafil (marketed in the US under the brand name STENDRA(™)) has been developed by VIVUS Inc. (Mountain View, CA, USA) and has recently received approval from the US Food and Drug Administration (FDA) for use in the treatment of male ED. The drug has demonstrated improved selectivity for PDE5, is rapidly absorbed after oral administration with a fast onset of action and a plasma half-life that is comparable to sildenfil and vardenafil. In phase II and phase III clinical trials that included a large number of patients, avanafil has been shown to be effective and well tolerated. Owing to its favorable pharmacodynamic and pharmacokinetic profile, avanafil is considered as a promising new option in the treatment of ED. The present article summarizes the initial data and clinical key properties of avanafil.

Erectile dysfunction

Erectile dysfunction is a common clinical entity that affects mainly men older than 40 years. In addition to the classical causes of erectile dysfunction, such as diabetes mellitus and hypertension, several common lifestyle factors, such as obesity, limited or an absence of physical exercise, and lower urinary tract symptoms, have been linked to the development of erectile dysfunction. Substantial steps have been taken in the study of the association between erectile dysfunction and cardiovascular disease. Erectile dysfunction is a strong predictor for coronary artery disease, and cardiovascular assessment of a non-cardiac patient presenting with erectile dysfunction is now recommended. Substantial advances have occurred in the understanding of the pathophysiology of erectile dysfunction that ultimately led to the development of successful oral therapies, namely the phosphodiesterase type 5 inhibitors. However, oral phosphodiesterase type 5 inhibitors have limitations, and present research is thus investigating cutting-edge therapeutic strategies including gene and cell-based technologies with the aim of discovering a cure for erectile dysfunction.

Density and distribution of connexin 43 in corpus cavernosum tissue from diabetic and hypogonadal patients with erectile dysfunction

Altered expression of connexin 43 (Cx43) has been postulated to be involved in the development and progression of various diseases including erectile dysfunction (ED). The aim of this study was to determine whether distribution and density of the gap junction protein Cx43 are altered in human corpus cavernosum (HCC) tissue samples derived from diabetic or hypogonadal patients with ED compared to those from normal subjects.

HCC tissue sections derived from normal, diabetic and hypogonadal subjects were fixed in 4% formaldehyde, embedded in paraffin and immunostained with a monoclonal mouse anti-rat Cx43 antibody. Cx43 density was expressed as the cumulative number of gap junction plaques per unit area of tissue corrected for number of 4′,6-diamidino-2-phenylindole, dihydrochloride-labeled smooth muscle cells (dots per unit area corrected for number of cells).

The distribution of Cx43 plaques in smooth muscle was not affected in tissues derived from diabetic or hypogonadal subjects with ED compared with those from normal subjects. However, the number of Cx43 plaques was significantly reduced in HCC tissues derived from diabetic or hypogonadal subjects (73±8% and 68±11% of normal, respectively), indicating reduced Cx43 gap junctions in diabetic and hypogonadal subjects with ED.

Cx43 density in the HCC was diminished in tissue samples derived from diabetic or hypogonadal patients with ED compared to tissue samples from normal non-diabetic subjects. This marked decrease in Cx43 gap junction channels may contribute to attenuated gap junction function and to diminished erectile physiology.

Avanafil for the treatment of erectile dysfunction: a multicenter, randomized, double-blind study in men with diabetes mellitus

OBJECTIVE

To prospectively assess the safety and effectiveness of the investigational phosphodiesterase 5 inhibitor avanafil to treat erectile dysfunction in men with diabetes mellitus.

PATIENTS AND METHODS

This 12-week, multicenter, double-blind, placebo-controlled study conducted between December 15, 2008, and February 11, 2010, randomized 390 men with diabetes and erectile dysfunction 1:1:1 to receive avanafil, 100 mg (n=129), avanafil, 200 mg (n=131), or placebo (n=130). Coprimary end points assessed changes in the percentage of sexual attempts in which men were able to maintain an erection of sufficient duration to have successful intercourse (Sexual Encounter Profile [SEP] 3), percentage of sexual attempts in which men were able to insert the penis into the partner's vagina (SEP 2), and International Index of Erectile Function erectile function domain score.

RESULTS

Compared with placebo, least-squares mean change from baseline to study end in SEP 3, SEP 2, and International Index of Erectile Function erectile function domain score were significantly improved with both avanafil, 100 mg (P≤.002), and avanafil, 200 mg (P<.001). Additional analyses indicated that successful intercourse could be initiated in 15 minutes or less through more than 6 hours after avanafil dosing. Adverse events most commonly reported with avanafil treatment were headache, nasopharyngitis, flushing, and sinus congestion.

CONCLUSION

Avanafil was safe and effective for treating erectile dysfunction in men with diabetes and was effective as early as 15 minutes and more than 6 hours after dosing. The adverse events seen with avanafil were similar to those seen with other phosphodiesterase 5 inhibitors.

TRIAL REGISTRATION

clinicaltrials.gov Identifier NCT00809471.

Exploring the structure determinants of pyrazinone derivatives as PDE5 3HC8 inhibitors: an in silico analysis

Phosphodiesterase type 5 (PDE5) inhibitors are clinically indicated for the treatment of erectile dysfunction, pulmonary hypertension and various other diseases. In this work, both ligand- and receptor-based three-dimensional quantitative structure-activity relationship (3D-QSAR) studies were carried out using comparative molecular field analysis (CoMFA) and comparative molecular similarity indices analysis (CoMSIA) techniques on 122 pyrazinone derivatives as PDE inhibitors. The resultant optimum 3D-QSAR model exhibits a proper predictive ability as indicated by the statistical results of Q² of 0.584, R(ncv)² of 0.884 and R(pre)² of 0.817, respectively. In addition, docking analysis and molecular dynamics (MD) simulation were also applied to elucidate the probable binding modes of these inhibitors. Our main findings are: (1) Introduction of bulky, electropositive and hydrophobic substituents at 12- and 19-positions can increase the biological activities. (2) N atom at 8-position is detrimental to the inhibitor activity, and the effect of N atoms at 5- and 6-positions on compound activity is co-determined by both the hydrophobic force and the π-π stacking interaction. (3) Bulky and hydrophilic substitutions are favored at the 27-position of ring D. (4) Electronegative and hydrophilic substitutions around 5- and 6-positions increase the inhibitory activity. (5) Hydrophobic forces and π-π stacking interaction with Phe786 and Phe820 are crucial in determining the binding of pyrazinone derivatives to PDE5. (6) Bulky substitutions around ring C favors selectivity against PDE11, while bulky groups near the 21-position disfavor the selectivity. The information obtained from this work can be utilized to accurately predict the binding affinity of related analogues and also facilitate future rational designs of novel PDE5 inhibitors with improved activity and selectivity.

Chronic low dosing of phosphodiesterase type 5 inhibitor for erectile dysfunction

Oral phosphodiesterase type 5 (PDE5) inhibitors have provided non-invasive, effective, and well-tolerated treatments for patients with erectile dysfunction (ED). However, many patients with ED are unresponsive to 'on-demand' PDE5 inhibitors. In addition, the lack of spontaneity and naturalness of the on-demand regimen could be a reason for decreased compliance with PDE5 inhibitors. Recently, tadalafil and udenafil were approved for low-dose daily administration for the treatment of ED. Since the introduction of the concept of daily administration of PDE5 inhibitors, several reports have supported the potential benefits of this therapy for disease modification, improvement of the treatment response in difficult-to-treat populations, spontaneity, and safety, although further research is needed to better address these hypotheses. In this article, we reviewed the daily administration of PDE5 inhibitors in terms of pharmacokinetics, safety, efficacy, and distinct features.

Dropout in the treatment of erectile dysfunction with PDE5: a study on predictors and a qualitative analysis of reasons for discontinuation

INTRODUCTION

Phosphodiesterase type 5 inhibitors (PDE5) are currently the first line treatment for erectile dysfunction (ED). However, previous research shows that PDE5 treatments have high discontinuation rates. Understanding the reasons for discontinuing PDE5 will be necessary to optimize the response to treatment.

AIM

The main goals were: (i) to analyze discontinuation rate of PDE5; (ii) to identify the discontinuation predictors; and (iii) to study the reasons for discontinuation using a qualitative methodology.

MAIN OUTCOME MEASURES

The PDE5 discontinuation rates, predictors, and reasons for discontinuation treatment.

METHODS

A total of 327 men with clinical diagnosis for ED who had been treated with PDE5 were successfully interviewed by telephone, after giving their informed consent by snail mail. Telephone interviews, concerning their ongoing treatment, were carried out using a standardized questionnaire form with quantitative and qualitative items. Participation rate was 71.8%.

RESULTS

Of the total sample, 160 men (48.9%) had discontinued PDE5 treatment. The discontinuation rate was higher among men with diabetes (73%) and in iatrogenic group (65%), and lower in venogenic etiology (38.7%). We differentiated three groups of men who discontinued treatment (i) during the first 3 months (55.1%); (ii) between 4 and 12 months (26.9%); and (iii) after a period of 12 months (18%). Qualitative analyses revealed diverse reasons for discontinuation: non-effectiveness of PDE5 (36.8%), psychological factors (e.g., anxiety, negative emotions, fears, concerns, dysfunctional beliefs) (17.5%), erection recovery (14.4%), and concerns about the cardiovascular safety of PDE5 (8.7%) were the most common. Older men and men whose partners were involved in the treatment, were less likely to discontinue treatment.

CONCLUSION

Half the subjects discontinued medication. Mostly, there was a combination of factors that led to discontinuation: non-effectiveness and psychosocial factors appear to be the main reasons. Addressing those factors will allow following up with appropriate focus on relevant topics in order to improve compliance.

Erectile properties of the Rho-kinase inhibitor SAR407899 in diabetic animals and human isolated corpora cavernosa

Background

RhoA-Rho kinase complex contributes to keep the cavernosus smooth muscle contracted and its inhibition is considered a potential strategy for the therapy of erectile dysfunction (ED).

Methods

We compared the effects of SAR407899, the Rho-kinase inhibitor Y-27632 and the PDE5 inhibitor sildenafil for their ability to relax corpus cavernosum strips contracted with phenylephrine in healthy and diabetic animals. Strips were obtained from WKY, spontaneous hypertensive (SHR), control CD, and diabetic CD rats, humans, control and diabetic rabbits. Diabetes was induced by streptozotocin or alloxan injection. In vivo penile erection (length) induced by drugs was measured in conscious rabbits.

Results

SAR407899 dose-dependently relaxed the pre-contracted corpora cavernosa in all species, with similar potency and efficacy in healthy vs diabetic rats, WKY vs SHR rats, healthy vs diabetic rabbits (IC₅₀ range from 0.05 to 0.29 μM, Emax range 89 to 97%). In the presence of the NO-synthase (NOS) inhibitor, L-NAME, the SAR407899 response did not decrease in any of the species or experimental conditions. The effect was confirmed in human strips where sildenafil was significantly less potent and effective, with IC₅₀ respectively 0.13 and 0.51 μM; Emax 92 and 43%. Unlike SAR407899, the potency and efficacy of sildenafil and Y27632 were significantly reduced by diabetes and L-NAME. In vivo, SAR407899 dose-dependently induced rabbit penile erection, with greater potency and longer duration of action than sildenafil. Sildenafil, but not SAR407899, was less effective in alloxan-induced diabetes.

Conclusion

The induction of penile erection by SAR407899, unlike that by sildenafil, is largely independent of e-NO activity. This suggests its use in erectile dysfunction for diabetic and hypertensive patients where e-NO activity is impaired.

A case-control analysis on the association between erectile dysfunction and sudden sensorineural hearing loss in Taiwan

INTRODUCTION

Although the cause of sudden sensorineural hearing loss (SSNHL) is yet to be elucidated, many theories have been proposed regarding potentially contributory etiologies. One increasingly well-supported theory purports an underlying vascular pathomechanism. If this is the case, SSNHL may also associate with conditions comorbid with vascular diseases, such as erectile dysfunction (ED). However, no studies to date have investigated the association between ED and SSNHL.

AIM

This study set out to estimate a putative association between ED and having been previously diagnosed with SSNHL using a population-based dataset with a case-control design.

METHODS

This study used administrative claim data from the Taiwan National Health Insurance program. We identified 4,504 patients with ED as the study group and randomly selected 22,520 patients as the comparison group. Conditional logistic regression was used to examine the association between ED and having previously received a diagnosis of SSNHL.

MAIN OUTCOME MEASURE

The prevalence and risk of SSNHL between cases and controls were calculated.

RESULTS

Of the sampled patients, 41 (0.15%) had been diagnosed with SSNHL before the index date; 22 (0.49% of the cases) were from the study group and 19 (0.08% of controls) were from the control group. Conditional logistic regression analysis revealed that after adjusting for the patient's monthly income, geographic location, hypertension, diabetes, hyperlipidemia, coronary heart disease, obesity, and alcohol abuse/alcohol dependence syndrome status, patients with ED were more likely than controls to have been diagnosed with SSNHL before the index date (odds ratio = 6.06, 95% confidence interval = 3.25-11.29).

CONCLUSIONS

There was an association between ED and prior SSNHL. The results of this study add to the evidence supporting an underlying vascular pathomechanism regarding the development of SSNHL and highlight a need for clinicians dealing with SSNHL patients to be alert to the development of ED.