Phosphodiesterase 5 Inhibitors in Rapid Ejaculation

Phosphodiesterase Type 5 Inhibitors in Male Reproduction: Molecular Mechanisms and Clinical Implications for Fertility Management

Phosphodiesterases, particularly the type 5 isoform (PDE5), have gained recognition as pivotal regulators of male reproductive physiology, exerting significant influence on testicular function, sperm maturation, and overall fertility potential. Over the past several decades, investigations have expanded beyond the original therapeutic intent of PDE5 inhibitors for erectile dysfunction, exploring their broader reproductive implications. This narrative review integrates current evidence from in vitro studies, animal models, and clinical research to clarify the roles of PDEs in effecting the male reproductive tract, with an emphasis on the mechanistic pathways underlying cyclic nucleotide signaling, the cellular specificity of PDE isoform expression, and the effects of PDE5 inhibitors on Leydig and Sertoli cell functions. Although certain findings suggest potential improvements in sperm motility, semen parameters, and a more favorable biochemical milieu for spermatogenesis, inconsistencies in study design, limited sample sizes, and inadequate long-term data temper definitive conclusions. Addressing these gaps through standardized protocols, larger and more diverse patient cohorts, and explorations of mechanistic biomarkers could pave the way for incorporating PDE5 inhibitors into evidence-based fertility treatment strategies. In the future, such targeted approaches may inform individualized regimens, optimize male reproductive outcomes, and refine the clinical application of PDE5 inhibitors as part of comprehensive male fertility management.

Efficacy of Various Treatment in Premature Ejaculation: Systematic Review and Network Meta-Analysis

PURPOSE

To investigate the various strategies used for the treatment of premature ejaculation (PE); these encompassed behavioral, drug and surgical interventions.

MATERIALS AND METHODS

We retrieved data from electronic literature searches of PubMed and Cochrane library using the MeSH (Medical Subject Headings terms) and text keywords from the earliest available date of indexing through September 2022. The subject headings and text keywords included those related to the population (male patients with PE), interventions & comparisons (mono and combination treatment), and outcomes (ejaculation latency time, ELT).

RESULTS

The initial search identified a total of 454 articles from electronic databases. Finally, a total of 10,474 patients from 59 direct comparison trials were included 143 effect sizes with 43 treatments. Of these, 9 of mono treatments and 4 of combination treatments were statistically significant. Pharmaceutical agents commonly used for patients with PE are prescribed off-label, except for dapoxetine. The surface under the cumulative ranking curve values of ranking probabilities for each treatment performance, which indicated that tramadol 100 mg ranked first in terms of ELT.

CONCLUSIONS

Medications recommended by the American Urological Association and the Sexual Medicine Society of North America were all incorporated within the present review, together with additional management approaches that have been evaluated in randomized controlled trials. The findings indicated that in addition to SSRIs, tramadol, clomipramine, topical agents and PDE5 inhibitors could be used in the therapy of PE.

Combined on-demand sildenafil citrate and tramadol hydrochloride is an effective and safe treatment for premature ejaculation: A randomized placebo-controlled double-blind clinical trial

Background

Premature ejaculation (PE) is a common sexual dysfunction that harms both sex partners.

Aim

To evaluate the safety, efficacy and impact on sexual satisfaction scores of the combined use of tramadol HCl and sildenafil citrate for the treatment of PE.

Methods

One hundred and sixty otherwise healthy males complaining of PE (primary/secondary) were enrolled in this randomized, double-blind, placebo-controlled study. Only 155 patients (age range 22-48 years) completed the study. Of them, 81 patients had primary PE, and 74 had secondary PE. The comparative groups included the placebo group (n = 34), sildenafil citrate 50 mg group (n = 39), tramadol HCl 100 mg group (n = 40), and the combination therapy group (n = 42). The treatment duration for all groups was 10 weeks.

Outcomes

This combination is safe and effective.

Results

Five patients discontinued the study, all from the placebo group, due to a lack of improvement over the treatment course. No significant differences were reported between groups before treatment as regards Intravaginal ejaculatory Latency Time (p = 0.8), satisfaction score (p = 0.7), age (p = 0.9), or duration of marriage (p = 0.9). There was a significant improvement in IELT after treatment with a placebo (p = 0.0001), associated with an insignificant improvement in satisfaction score (p = 1.0). In the other three groups, there was a significant improvement in IELT after treatment (p = 0.0001 for all), which coincided with a significant improvement in satisfaction scores in all three groups (p = 0.0001 for all).

Clinical Implications

We recommend this combination in the treatment of premature ejaculation.

Strengths

It is a prospective randomized double-blind placebo-controlled clinical trial.

Limitations

Limited number of participants.

Conclusion

Combined therapy of PE, whether primary or secondary, with sildenafil citrate 50 mg and tramadol HCl 100 mg is safe and effective; and its therapeutic effect is superior to the utilization of either agent alone.

Phosphodiesterase type 5 inhibitors and premature ejaculation: an overview of systematic reviews/meta-analyses using the AMSTAR 2, ROBIS, and GRADE tools

Introduction

The place of phosphodiesterase type 5 inhibitors (PDE5-Is) in treating premature ejaculation (PE) remains a therapeutic challenge.

Objectives

(1) To summarize the evidence of the efficacy and safety of PDE5-Is from published systematic reviews/meta-analyses (SRs/MAs). (2) To evaluate the reporting, methodological quality, and evidence quality of SRs/MAs concerning PE.

Methods

Nine databases were searched to retrieve SRs/MAs on using PDE5-Is for PE from inception to July 2022. Methodological quality and risk of bias were assessed with the AMSTAR 2 (A Measurement Tool to Assess Systematic Reviews) and ROBIS (Risk of Bias in Systematic Reviews). GRADE criteria (Grading of Recommendations, Assessment, Development, and Evaluations) were used to assess the evidence quality.

Results

The literature search revealed 15 relevant SRs/MAs covering 28 primary studies (9 pairwise MAs and 6 network MAs) rated as low or very low quality and high risk of bias except 1 review that was rated as moderate quality and low risk of bias. Among the 27 outcome measures related to efficacy and safety, the quality of evidence according to GRADE criteria was low in 4 and critically low in 23. Oral PDE5-Is have demonstrated a possible benefit over placebo in lifelong PE and mixed PE. The results of pairwise and network MAs advocated that the combined use of PDE5-Is and SSRIs is of possible benefit as compared with either SSRIs or PDE5-Is alone. The total adverse effects were more frequent with PDE5-Is than placebo.

Conclusion

PDE5-Is are of a possible benefit than placebo in lifelong PE and mixed PE. The results favor coadministration of PDE5-Is plus SSRIs over SSRIs alone or PDE5-I monotherapy. These conclusions should be interpreted cautiously due to the low methodological quality and low quality of evidence of most available reviews. Additional higher-quality randomized controlled trials, SRs, and MAs are warranted to provide a better estimate of any effect size.

PDE5 inhibitors and male reproduction: Is there a place for PDE5 inhibitors in infertility clinics or andrology laboratories?

The objective of this review study is to evaluate the therapeutic role of PDE5 inhibitors (PDE5is) in the amelioration of oligoasthenospermia in infertile males. PDE5is have a beneficial influence on the secretory function of the Leydig and Sertoli cells, the biochemical environment within the seminiferous tubule, the contractility of the testicular tunica albuginea, and the prostatic secretory function. In several studies, the overall effect of sildenafil and vardenafil increased quantitative and qualitative sperm motility. Furthermore, some studies indicate that PDE5is influence positively the sperm capacity to undergo capacitation under biochemical conditions that are known to induce the sperm capacitation process. Additional research efforts are necessary in order to recommend unequivocally the usage of sildenafil, vardenafil, or avanafil for the alleviation of male infertility.

An update on the treatment of premature ejaculation: A systematic review

To analyse the current therapeutic options for patients with premature ejaculation (PE) and highlight their mechanism(s) of action, effectiveness, advantages and limitations. A literature search was conducted using the PubMed database searching for articles exploring different PE treatment modalities. A Preferred Reporting Items for Systemic Reviews and Meta-Analyses (PRISMA) approach was used to report the results of the literature search. A total of 149 articles were included in this review. The currently available treatment methods for PE include behavioural therapy, local anaesthetics, tricyclic antidepressants, selective serotonin reuptake inhibitors, and selective phosphodiesterase inhibitors. Most PE treatments are either experimental or used off-label. New treatments are certainly warranted to overcome this exasperating sexual dysfunction.

Abbreviations: AIPE: Arabic Index of Premature Ejaculation; CNS: central nervous system; CYP: cytochrome P450; ED: erectile dysfunction; FDA: United States Food and Drug Administration; H1: histamine receptors; 5-HT: 5-hydroxytryptamine; IELT: The intravaginal ejaculation latency time; IPE: Index of Premature Ejaculation; M1: muscarinic receptors; OCD: obsessive–compulsive disorder; PDE5: phosphodiesterase type 5; PE: premature ejaculation; PEP: Premature Ejaculation Profile; PRO: patient-reported outcome; RCT: randomised controlled trial; SS: Severance Secret (cream); SSRIs: selective serotonin reuptake inhibitors; TCAs: tricyclic antidepressants

Effect of tadalafil 5mg daily treatment on the ejaculatory times, lower urinary tract symptoms and erectile function in patients with erectile dysfunction

Objective

To investigate the effect of a 5mg daily tadalafil treatment on the ejaculation time, erectile function and lower urinary tract symptoms (LUTS) in patients with erectile dysfunction.

Materials and Methods

A total of 60 patients diagnosed with erectile dysfunction were retrospectively evaluated using the international index of erectile function questionnaire-5 (IIEF-5), intravaginal ejaculatory latency time (IELT) and international prostate symptoms scores (IPSS). After the patients were treated with 5mg tadalafil once a day for three months, their erection, ejaculation and LUTS were assessed again. The fasting levels of blood glucose, total testosterone, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol and total cholesterol were measured. The independent-samples t-test was used to compare the pre- and post-treatment scores of the patients.

Results

The mean age of the 60 participants was 50.4±7.9 and the mean baseline serum total testosterone, total cholesterol, and fasting blood sugar were 444.6±178.6ng dL^-1, 188.7±29.6mg/dL^-1,104 (80-360) mg dL^-1, respectively. The mean baseline scores were 2.2±1.4 min for IELT, 9.5±3.7 for IIEF-5 and 14.1±4.5 for IPSS. Following the three-month daily 5mg tadalafil treatment, the scores were found to be 3.4±1.9 min, 16.1±4.7, and 10.4±3.8 for IELT, IIEF and IPSS, respectively. When the baseline and post-treatment scores were compared, a statistically significant increase was observed in the IELTs and IIEF-5 values whereas there was a significant decrease in IPSS (p<0.01).

Conclusion

A daily dose of 5mg tadalafil can be safely used in the treatment of erectile dysfunction and LUTS, that prolongs the ejaculatory latency time.

Comparison of the clinical efficacy and safety of the on-demand use of paroxetine, dapoxetine, sildenafil and combined dapoxetine with sildenafil in treatment of patients with premature ejaculation: A randomised placebo-controlled clinical trial

The aim of the study was to compare the clinical efficacy and safety of the on-demand use of paroxetine, dapoxetine, sildenafil and combined dapoxetine with sildenafil in treatment of patients with premature ejaculation (PE). In a single-blind placebo-controlled clinical study, 150 PE patients without erectile dysfunction (ED) were included during the period of March 2015 to May 2016. Patients were randomly divided into five groups (30 patients each). On demand placebo, paroxetine (30 mg), dapoxetine (30 mg), sildenafil citrate (50 mg) and combined dapoxetine (30 mg) with sildenafil citrate (50 mg) were given for patients for 6 weeks in each group respectively. All patients were instructed to record intravaginal ejaculatory latency time (IELT) and evaluated with Premature Ejaculation Diagnostic Tool (PEDT) and the patient satisfaction score before and after treatment. The mean of IELT, satisfaction score and PEDT in all groups was significantly improved after treatment (p value = .001). Combined dapoxetine with sildenafil group had the best values of IELT, satisfaction scores and PEDT in comparison with other treatment groups (p value <.001). The combined dapoxetine with sildenafil therapy could significantly improve PE patients without ED as compared to paroxetine alone or dapoxetine alone or sildenafil alone with tolerated adverse effects.

Pharmacodynamics, pharmacokinetics and clinical efficacy of phosphodiesterase-5 inhibitors

INTRODUCTION

Phosphodiesterase type 5 inhibitors (PDE5Is) are the first-line drugs in the management of erectile dysfunction (ED). However, over the past two decades tremendous efforts have been made to identify new clinical uses of PDE5Is beyond their roles in ED. Areas covered: Basic science articles, clinical trials, reviews, and meta-analysis published between 1996 and 2015 were searched using MEDLINE (PubMed interface) to collect the most relevant and impactful studies from our perspectives as practicing urologists. This review mainly focuses on the level one evidence-based clinical efficacy and drug-related toxicity of oral PDE5Is. In addition, drug discovery, pharmacokinetics and pharmacodynamics, potential use in other diseases, and future directions are discussed. Expert opinion: On-demand PED5Is for the treatment of ED has shifted toward chronic administration in a broad spectrum of conditions that are thought to be associated with endovascular health. Several studies have shown that PDE5Is may play a cardioprotective or neuroprotective role. Further studies are under way to verify beneficial effects of PDE5I in non-urological conditions.

Current and Emerging Treatments for Premature Ejaculation

INTRODUCTION

Over the past 20-30 years, the premature ejaculation (PE) treatment paradigm, previously limited to behavioral psychotherapy, has expanded to include drug treatment. Pharmacotherapy for PE predominantly targets the multiple neurotransmitters and receptors involved in the control of ejaculation, which include serotonin, dopamine, oxytocin, norepinephrine, gamma amino-butyric acid (GABA) and nitric oxide (NO).

AIM

The objective of this article is to review current and emerging PE interventions.

METHODS

Contemporary data on the treatment of PE were reviewed and critiqued using the principles of evidence-based medicine.

MAIN OUTCOME MEASURE

Integrated pharmacotherapy and cognitive behavioral therapy (CBT) may achieve superior treatment outcomes in some patients. Phosphodiesterase type 5 inhibitors alone or in combination with selective serotonin reuptake inhibitors (SSRIs) should be limited to men with acquired PE secondary to comorbid erectile dysfunction (ED). New on-demand rapid-acting SSRIs, oxytocin receptor antagonists, or single agents that target multiple receptors may form the foundation of more effective future on-demand medication.

RESULTS

Multiple well-controlled evidence-based studies have demonstrated the efficacy and safety of SSRIs in delaying ejaculation, confirming their role as first-line agents for the medical treatment of lifelong and acquired PE. Daily dosing of SSRIs is likely to be associated with superior fold increases in intravaginal ejaculation latency time compared with on-demand SSRIs. On-demand SSRIs are less effective but may fulfill the treatment goals of many patients.

CONCLUSIONS

Current evidence suggests that psychosexual CBT has a limited role in the contemporary management of PE and confirms the efficacy and safety of dapoxetine, off-label SSRI drugs, and topical anesthetics drugs. Treatment with tramadol, α1-adrenoceptor antagonists cannot be recommended until the results of large, well-designed randomized controlled trials are published in major international peer-reviewed medical journals. As our understanding of the neurochemical control of ejaculation improves, new therapeutic targets and candidate molecules will be identified, which may increase our pharmacotherepeutic armamentarium. McMahon CG. Current and emerging treatments for premature ejaculation. Sex Med Rev 2015;3:183-202.

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.

Vas deferens smooth muscle responses to the nitric oxide-independent soluble guanylate cyclase stimulator BAY 41-2272

The nitric oxide-cGMP signaling pathway modulates the ejaculatory functions. The nitric oxide (NO)-independent soluble guanylate cyclase haem-dependent stimulator BAY 41-2272 potently relaxes different types of smooth muscles. However, no study investigated its effects in vas deferens smooth muscle. Therefore, we designed experiments to evaluate the in vitro relaxing responses of vas deferens to BAY 41-2272. The effects of prolonged oral intake with BAY 41-2272 in vas deferens contractions of rats treated chronically with the NO synthase inhibitor N(ω)-nitro-L-arginine methyl ester (L-NAME) were also investigated. BAY 41-2272 (0.001-100 μM) produced concentration-dependent relaxations in the prostatic and epididymal portions of vas deferens, an effect markedly reduced by the soluble guanylate cyclase inhibitor ODQ (100 μM). BAY 41-2272 significantly increased cGMP levels that were fully prevented by ODQ. In separate protocols, rats received L-NAME (20mg/rat/day) concomitantly with BAY 41-2272 (10mg/kg/day, 4 weeks), after which vas deferens contractions to electrical-field stimulation and noradrenaline were achieved. Electrical-field stimulation (1-32 Hz) evoked frequency-dependent contractions that were significantly enhanced in L-NAME-treated rats. Co-treatment with BAY 41-2272 fully reversed the increased contractile responses in L-NAME group. Noradrenaline (0.01-100 μM)-induced contractions were also greater in L-NAME-treated rats, and that was normalized by BAY 41-2272. In conclusion, BAY 41-2272 potently relaxes in vitro rat vas deferens smooth muscle and elevates the cGMP levels in an ODQ-sensitive manner. Moreover, prolonged oral intake with BAY 41-2272 restores the enhanced contractile vas deferens activity in rats treated with L-NAME. NO-independent soluble guanylate cyclase stimulators may be an alternative treatment for premature ejaculation.

Purinergic contraction of the rat vas deferens in L-NAME-induced hypertension: effect of sildenafil

Hypertension (HTN) is a risk factor for erectile dysfunction, but its effect on vas deferens (VD) contractility and the ejaculatory response has not been delineated. NG-nitro-L-arginine methyl ester (L-NAME), a nitric oxide synthase inhibitor, was used for induction of nitric oxide (NO)-deficient HTN. Our aim was to evaluate the effects of L-NAME-induced HTN on rat VD contractility and to determine whether sildenafil affects VD contractility. A total of 36 male rats were divided into (1) control, (2) L-NAME-HTN, (3) sildenafil treated L-NAME-HTN groups. Group 2 was treated with L-NAME (40 mg kg(-1) per day) in drinking water for 4 weeks. Group 3 received sildenafil (1.5 mg kg(-1) per day, by oral gavage) concomitantly with L-NAME. The prostatic portion of the VD was subjected to electrical field stimulation (EFS, 1-20 Hz), and the P2X(1) agonist alpha,beta-methylene ATP (alpha,beta-meATP, 100 micromol L(-1)-1 micromol L(-1)) and the alpha1-adrenoceptor agonist phenylephrine (Phe, 100 micromol L(-1)-1 mmol L(-1)) were used to construct concentration-response curves. These experiments were repeated in the presence of P2X receptor antagonist, pyridoxalphosphate-6-azophenyl-2',4'-disulfonic acid (PPADS, 30 micromol L(-1)). VD contractions in response to EFS, alpha,beta-meATP and Phe were significantly enhanced by L-NAME. Sildenafil treatment in the L-NAME group improved the contractile response of VD to EFS (20 Hz). In the presence of PPADS, the enhanced contractile response of VD to EFS and alpha,beta-meATP in hypertensive rats was reversed. In the rat model of chronic NO depletion, the purinergic and adrenergic components and EFS affect VD contractility. The VD contractile response may be mediated more by the purinergic system than the adrenergic system, and sildenafil may alter the ejaculatory response in men with PE.

Putative role of carbon monoxide signaling pathway in penile erectile function

INTRODUCTION

Erectile response depends on nitric oxide (NO) generated by NO synthase (NOS) enzyme of the nerves and vascular endothelium in the cavernous tissue. NO activates soluble guanylate cyclase (sGC), leading to the production of cyclic guanosine monophosphate (cGMP). cGMP activates cGMP-dependent protein kinase that activates Ca(2+)/ATPase pump that activates Ca(2+)/K efflux pump extruding Ca(2+) across the plasma membrane with consequent smooth muscle cell relaxation. A role similar to that of NOS/NO signaling has been postulated for carbon monoxide (CO) produced in mammals from heme catabolism by heme oxygenase (HO) enzyme.

AIM

To assess CO signaling pathway for erectile function by reviewing published studies.

METHODS

A systematic review of published studies on this affair based on Pubmed and Medical Subject Heading databases, with search for all concerned articles.

MAIN OUTCOME MEASURES

Documentation of positive as well as negative criteria of CO/HO signaling focused on penile tissue.

RESULTS

The concept that HO-derived CO could play a role in mediating erectile function acting in synergism with, or as a potentiator for, NOS/NO signaling pathway is gaining momentum. CO/HO signaling pathway has been shown to partially mediate the actions of oral phosphodiesterase type 5 inhibitors. In addition, it was shown that the use of CO releasing molecules potentiated cavernous cGMP levels. However, increased CO production or release was reported to be associated, in some studies, with vasoconstriction.

CONCLUSION

This review sheds a light on the significance of cavernous tissue CO signaling pathway that may pave the way for creation of therapeutic modalities based on this pathway.

An insight into the pharmacophores of phosphodiesterase-5 inhibitors from synthetic and crystal structural studies

Selective inhibitors of cyclic nucleotide phosphodiesterase-5 (PDE5) have been used as drugs for treatment of male erectile dysfunction and pulmonary hypertension. An insight into the pharmacophores of PDE5 inhibitors is essential for development of second generation of PDE5 inhibitors, but has not been completely illustrated. Here we report the synthesis of a new class of the sildenafil derivatives and a crystal structure of the PDE5 catalytic domain in complex with 5-(2-ethoxy-5-(sulfamoyl)-3-thienyl)-1-methyl-3-propyl-1,6-dihydro-7H-pyrazolo[4,3-d]pyrimidin-7-one (12). Inhibitor 12 induces conformational change of the H-loop (residues 660-683), which is different from any of the known PDE5 structures. The pyrazolopyrimidinone groups of 12 and sildenafil are well superimposed, but their sulfonamide groups show a positional difference of as much as 1.5A. The structure-activity analysis suggests that a small hydrophobic pocket and the H-loop of PDE5 are important for the inhibitor affinity, in addition to two common elements for binding of almost all the PDE inhibitors: the stack against the phenylalanine and the hydrogen bond with the invariant glutamine. However, the PDE5-12 structure does not provide a full explanation to affinity changes of the inhibitors. Thus alternatives such as conformational change of the M-loop are open and further structural study is required.

Tadalafil and fluoxetine in premature ejaculation: prospective, randomized, double-blind, placebo-controlled study

INTRODUCTION

Premature ejaculation (PE) is a common male sexual disorder. An ideal, reliable and effective treatment is desired by many men and couples affected by this condition.

AIM

Evaluate if the association of a phosphodiesterase-5 inhibitor, tadalafil, and a selective serotonin reuptake inhibitor, fluoxetine, can prolong the intravaginal ejaculatory latency time (IELT) in men with lifelong premature ejaculation.

METHODS

Sixty patients with lifelong premature ejaculation and without erectile dysfunction (ED) with IELT less than 90 s were enrolled in the protocol and randomized into 4 groups to use a combination of medications: (1) tadalafil 20 mg plus fluoxetine 90 mg, (2) fluoxetine 90 mg plus placebo, (3) tadalafil 20 mg plus placebo, and (4) two different placebo capsules (control). Before starting the medications, each man timed his IELT with a stopwatch, and likewise during the treatment period. Fluoxetine 90 mg or placebo was taken once a week plus tadalafil 20 mg or placebo within a 36-hour frame of intended sexual intercourse with a steady partner. Patients were prospectively followed for 12 weeks. One-way ANOVA was used for statistical comparisons of IELT results in each group.

RESULTS

Mean IELT before starting treatment was 51.3 +/- 23 s. With one-way ANOVA, a statistically significant difference in post-treatment IELT was seen with combination treatment compared to placebo (p < 0.001). There were increases in IELT from baseline in patients using fluoxetine plus tadalafil (49.57 +/- 25.87 to 336.13 +/- 224.77) (p < 0.001), fluoxetine (56.55 +/- 18.55 to 233.62 +/- 105.08) (p < 0.001) and tadalafil (49.26 +/- 19.43 to 186.53 +/- 159.05) (p = 0.001). The increases in each group were statistically significant compared to the placebo (49.86 +/- 19.43 to 67.82 +/- 46.18) (p = 0.042).

CONCLUSION

Fluoxetine plus tadalafil significantly increased the IELT from baseline in men with lifelong premature ejaculation when compared to placebo, tadalafil or fluoxetine.

Sildenafil in the treatment of erectile dysfunction: an overview of the clinical evidence

Erectile dysfunction (ED) is a highly prevalent disease associated with aging as well as with several risk factors including hypertension, heart disease, obesity, dyslipidemia, diabetes, hypogonadism, drugs-related, and pelvic surgery. Many of these factors are components of the metabolic syndrome, a multiplex risk factor for cardiovascular disease (CVD). ED shares common risk factors with CVD. Endothelial dysfunction seems to be the early underlying pathophysiology across both conditions. The efficacy, tolerability and cardiovascular safety of sildenafil has been evaluated in numerous large, randomized, double-blind, placebo-controlled clinical studies in the broad population of men with ED including men with several co-morbid conditions. Sildenafil is effective in several specific patient populations including the difficult-to-treat subpopulations such as diabetes mellitus and after radical prostatectomy. It is associated with rapid onset of action – within 14 minutes for some men – and an extended duration of action for up to 12 hours. Sildenafil improves quality of life and satisfaction for treated men and is well tolerated with a favorable safety profile. New data suggest that sildenafil has beneficial effects in several chronic conditions. It has been approved for the treatment of idiopathic pulmonary hypertension. Numerous articles have suggested that it improves endothelial function and a possible role on premature ejaculation or treatment of lower urinary tract symptoms has been suggested.

Daily Administration of Phosphodiesterase Type 5 Inhibitors for Urological and Nonurological Indications

OBJECTIVES

Although the discovery of phosphodiesterases (PDEs) was made soon after the identification of cyclic adenosine monophosphate nearly half a century ago, their true importance in medicine has taken many decades to be realised. The recognition of the important role PDE enzymes play and the impact of altering intracellular cyclic nucleotide levels became significant for most urologists and clinicians in the early 1990s with the discovery of sildenafil, a PDE5 inhibitor (PDE5-I). Once approved around the world, on-demand use of PDE5-Is became the gold standard. Recently, the potential beneficial effects of PDE5-Is on the pulmonary, vascular, and other systems has led to examination of alternative dosing regimens. In this review, we have synthesised the available published peer-reviewed literature to provide a critical contemporary view of evolving indications for PDE5-Is and how alternative dosing regimens may impact on sexual and other functions.

METHODS

MEDLINE search of all peer-reviewed English literature for the period 1990-2007.

RESULTS

The plethora of articles detailing potential uses of PDE5-I in multiple fields of medicine was uncovered. Use of alternative dosing regimens shows great promise across a number of clinical indications, including post-radical retropubic prostatectomy, pulmonary hypertension, endothelial dysfunction, and salvage of on-demand PDE5-I nonresponders.

CONCLUSIONS

Use of PDE5-I on a daily basis may evolve into a major form of drug administration both for men with erectile dysfunction and for those with a myriad of other conditions shown to benefit from this approach.

The utility of sildenafil citrate for infertile men with sexual dysfunction: a pilot study

OBJECTIVE

To investigate the use the sildenafil citrate, recognized as a first-line therapy for men with erectile dysfunction (ED), and which is safe and effective in men with various causes and severity of ED, including psychogenic ED, in a population of infertile men with sexual dysfunction.

PATIENTS AND METHODS

Infertility is a major source of life stress and might be associated with sexual dysfunction through the erosion of self-esteem and self-confidence, and in stimulating discord in a relationship. Men presenting for evaluation of fertility who on questioning by the physician reported the recent onset of sexual dysfunction, had a history taken, a physical examination, hormonal profile, and completed the International Index of Erectile Function (IIEF), a validated inventory for assessing sexual dysfunction. Thirty men with a score of <26 on the erectile function domain of the IIEF, or who complained of new onset rapid or delayed ejaculation, were treated with sildenafil with no randomization or placebo control. The evaluation was repeated and the IIEF completed again > or =3 months after starting treatment.

RESULTS

For men complaining of ED, subjective erectile rigidity, duration of erection, and the percentage of successful penetration attempts significantly improved with sildenafil. The mean (sd) IIEF domain scores for erection and satisfaction, at 18 (4) vs 27 (3), and 12 (2) vs 16 (3) (both P = 0.01), and orgasm, at 4 (1) vs 6 (3) (P = 0.001), respectively, significantly improved after treatment. In patients with ejaculatory dysfunction, the function improved in 64% after sildenafil therapy.

CONCLUSIONS

We identified the nature of sexual dysfunction associated with male-factor infertility, and showed the efficacy of sildenafil therapy in men with this condition.

Functional Responses of Isolated Human Seminal Vesicle Tissue to Selective Phosphodiesterase Inhibitors

OBJECTIVES

To further elucidate the significance of the cyclic nucleotide-mediated signal transduction, we examined the in vitro functional responses of isolated seminal vesicle (SV) smooth muscle tissue to selective phosphodiesterase (PDE) inhibitors.

METHODS

Using the organ bath technique, the effects of increasing concentrations (1 nM to 10 microM) of the PDE inhibitors vinpocetine (PDE1 inhibitor), rolipram (PDE4 inhibitor), and sildenafil and vardenafil (PDE5 inhibitors) on the tension induced by 10 microM of norepinephrine on SV tissue strips were investigated. To examine the drug effects on the tissue levels of cyclic guanosine monophosphate (cGMP) and cyclic adenosine monophosphate (cAMP), the SV strips were exposed to different concentrations of the compounds (0.1, 1, and 10 microM). After freezing, homogenization, and extraction of cyclic nucleotides, cAMP and cGMP were measured using radioimmunoassays. In the experiments, sodium nitroprusside and forskolin were used as reference compounds.

RESULTS

The norepinephrine-induced tension was reversed by the drugs in a dose-dependent manner. The rank order of efficacy was rolipram greater than sildenafil greater than vardenafil greater than or equal to vinpocetine greater than sodium nitroprusside greater than forskolin. The reversion of the norepinephrine-induced tension at maximum drug concentration ranged from 79% (rolipram) to 32% (forskolin). Only rolipram and sildenafil reached a median effective concentration. The effects of the PDE inhibitors were paralleled by a 1.7-fold to 173-fold increase in tissue cGMP or cAMP.

CONCLUSIONS

Our results have demonstrated that PDE inhibitors can reverse the adrenergic tension of human SV tissue and increase levels of cyclic nucleotides. This outlines the potential significance of cAMP and cGMP in the control of SV smooth muscle function. These findings might be of importance with regard to the pharmacologic treatment of premature ejaculation.

A new combination treatment for premature ejaculation: a sex therapist's perspective

This article describes the diagnosis and treatment of premature ejaculation (PE) from a sex therapist's perspective and proposes that combination therapy integrating sex therapy and sexual pharmaceuticals is frequently the best treatment approach. Failure to appreciate the multimodal etiology and pathophysiology of PE makes the condition more difficult to diagnose and treat. Many physicians have tried pharmacologic approaches, but are limited to providing topical anesthetics or suggesting off-label uses of antidepressant and erectile dysfunction medications, because no medication is currently indicated specifically for PE. Furthermore, patients frequently relapse after discontinuation of the pharmaceutical. Sex therapists appreciate the multidimensional nature of PE for the patient and partner, but few patients seek out this approach, which is labor-intensive and often lacking long-term follow-up success. Most men with PE are not receiving treatment, secondary to their embarrassment about discussing their condition and a lack of clinician inquiry about sexual dysfunction. Even for those who do engage in discussion, diagnoses may be inconsistent, because a universally accepted definition of the condition and diagnostic criteria are nonexistent. Men with PE experience anxiety and lack sexual self-confidence; subsequently, their sexual and overall relationship frequently suffer. Because PE involves psychosocial and physiologic factors, treatment that addresses both should yield the best balance of function. There is interest in new agents designed specifically for PE to provide an improved pharmacotherapeutic opportunity. Yet, a combination treatment integrating pharmaceuticals and sex therapy would provide an optimized approach. Besides increasing coital latency directly, sexual pharmaceuticals could be used to provide greater opportunity for men to recognize their premonitory sensations to ejaculation more readily, facilitating a "choice point", which is key to facilitating behavioral change and learning. Such a combination approach would result in prolonged ejaculatory latency, improved treatment satisfaction, and superior long-term outcome.

Can sildenafil treat primary premature ejaculation? A prospective clinical study

BACKGROUND

Recently, sildenafil has been demonstrated to be effective in treating premature ejaculation (PE). However, these studies ignored female factors and could not exclude the probability of drug interaction when combined with paroxetine. Therefore, the aim of this study was to evaluate the efficacy and safety of sildenafil alone in the treatment of primary PE, taking female factors into consideration.

METHODS

One hundred and eighty potent men with primary PE were randomly divided into three groups and followed up for 6 months. Group A were treated with 50 mg sildenafil as needed, group B with 20 mg paroxetine daily and group C with squeeze technique daily. Intravaginal ejaculatory latency time (IELT), PE grade, intercourse satisfactory score (ISS), frequency of intercourse, and adverse effects of drugs were recorded before treatment, and 3 and 6 months after treatment.

RESULTS

Compared with pretreatment, the three groups had significant differences in all the parameters after 3 or 6 months treatment, except the frequency of intercourse in Group C (all P = 0.00). However, there were no significant differences between 3 and 6 months. Compared with paroxetine and squeeze technique, after 3 or 6 months, sildenafil had significant differences in all the parameters (all P = 0.00). After 6 months, 1.7%, 18.3% and 36.7% patients in groups A, B and C, respectively, withdrew from the study and 86.7%, 60.0% and 45.0% patients, respectively, wanted to be treated further with the original administration, and this was statistically significant (both P = 0.00).

CONCLUSION

Sildenafil is very effective and safe to treat PE, and has much higher efficacy than paroxetine and squeeze technique.

The psychology of premature ejaculation: therapies and consequences

INTRODUCTION

Premature ejaculation (PE) is a common male sexual dysfunction characterized by the loss or absence of ejaculatory control, marked distress or interpersonal difficulty and by a short intravaginal ejaculatory latency time (IELT). PE can impact both the patient's and his partner's quality of life.

AIM

To review evidence concerning the psychologic influences of PE on the self-esteem and self-confidence of men with PE and the impact on their partners. To review the role of psychotherapy in the management of men with PE.

METHODS

The Sexual Medicine Society of North America hosted a State of the Art Conference on Premature Ejaculation on June 24-26, 2005 in collaboration with the University of South Florida. The purpose was to have an open exchange of contemporary research and clinical information on PE. There were 16 invited presenters and discussants; the group focused on several educational objectives.

MAIN OUTCOME MEASURE

Peer-reviewed medical literature was reviewed concerning management of men with PE by psychologic and sexual therapy. Premature ejaculation has long been viewed as a psychological concern involving psychological interventions, although recent research also focuses on the neurobiological underpinnings of the dysfunction. Psychosexual therapies combine behavioral interventions to help the patient learn to control or delay his ejaculation and to assist him in regaining confidence and lessening performance anxiety. Psychosexual therapy can be combined with pharmacotherapies to provide an improved prognosis to the patient with PE.

CONCLUSIONS

Healthcare providers do not manage the majority of patients with PE with the same consideration and attention provided men with erectile dysfunction (ED). PE has been perceived as a psychological concern, either a learned behavior or a response to a meaningful event/interaction or sexual anxiety. Primary treatment has involved psychosexual therapy. Regardless of etiology, psychological/sexual therapy can play an important role in the management of PE.

Characterization of a catalytic ligand bridging metal ions in phosphodiesterases 4 and 5 by molecular dynamics simulations and hybrid quantum mechanical/molecular mechanical calculations

Cyclic nucleotide phosphodiesterases (PDEs) constitute a large superfamily of enzymes regulating concentrations of intracellular second messengers cAMP and cGMP through PDE-catalyzed hydrolysis. Although three-dimensional x-ray crystal structures of PDE4 and PDE5 have been reported, it is uncertain whether a critical, second bridging ligand (BL2) in the active site is H2O or HO- because hydrogen atoms cannot be determined by x-ray diffraction. The identity of BL2 is theoretically determined by performing molecular dynamics simulations and hybrid quantum mechanical/molecular mechanical (QM/MM) calculations, for the first time, on the protein structures resolved by x-ray diffraction. The computational results confirm our previous suggestion, which was based on QM calculations on a simplified active site model, that BL2 in PDE4 should be HO-, rather than H2O, serving as the nucleophile to initialize the catalytic hydrolysis of cAMP. The molecular dynamics simulations and QM/MM calculations on PDE5 demonstrate for the first time that the BL2 in PDE5 should also be HO- rather than H2O as proposed in recently published reports on the x-ray crystal structures, which serves as the nucleophile to initialize the PDE5-catalyzed hydrolysis of cGMP. These fundamental structural insights provide a rational basis for future structure-based drug design targeting PDEs.

Efficacy of sildenafil citrate in treatment of erectile dysfunction: Impact of associated premature ejaculation and low desire

OBJECTIVES

To assess the effect of premature ejaculation (PE) and low desire on the efficacy and satisfaction rate of sildenafil in the treatment of erectile dysfunction (ED).

METHODS

A total of 586 male patients with ED in association with and without PE or low desire were enrolled in this study. Patients were screened for ED using the International Index for Erectile Function. All patients were also screened for PE and low desire. We compared the responses to the erectile function domain, questions 3 and 4, before and after sildenafil in patients with and without PE or low desire. Overall satisfaction and global efficacy question responses were also assessed in all patients.

RESULTS

The mean age +/- SD was 58 +/- 6.4 years. Significant associations were found between the increased duration and severity of ED and the decreased rate of overall satisfaction. Before sildenafil administration, significant differences were found in the erectile function domain, Q3 and Q4 between patients with and without PE or low desire. After sildenafil administration, no significant differences were found in those assessment variables and the presence or absence of PE and low desire. No significant differences were found between the global efficacy question response and the overall satisfaction rate between patients with and without PE or low desire.

CONCLUSIONS

The efficacy of sildenafil was negatively affected by an increased duration and severity of ED; however, global efficacy and overall patient satisfaction were not attenuated by PE or low desire.

Etiology of ejaculation and pathophysiology of premature ejaculation

INTRODUCTION

Ejaculation is comprised of three stages of the male sexual response cycle, namely emission, ejection, and orgasm; however, in comparison with erection, which is a well-understood component of male sexual response, the pathophysiology of ejaculation has yet to be fully delineated. Premature ejaculation (PE), the most common sexual disorder in men, while believed to have a multifactorial etiology, is even less well understood.

AIM

This article reviews the physiology of ejaculation, and the multifactorial pathophysiology of PE.

METHODS

The Sexual Medicine Society of North America hosted a State of the Art Conference on Premature Ejaculation on June 24-26, 2005 in collaboration with the University of South Florida. The purpose was to have an open exchange of contemporary research and clinical information on PE. There were 16 invited presenters and discussants; the group focused on several educational objectives.

MAIN OUTCOME MEASURE

Data were obtained by extensive examination of published peer-reviewed literature.

RESULTS

Evidence supports that biologic mechanisms associated with neurotransmitters such as norepinephrine, serotonin, oxytocin, Gamma-amino-butyric acid, and nitric oxide (NO) as well as the hormone estrogen play central roles in ejaculation, and subsequently may mediate PE. There is also emerging evidence to show that hyperthyroidism may be a causal factor in PE. Recent data also suggest that psychogenic factors include high level of any experience by some men with PE.

CONCLUSIONS

The pathophysiology of both lifelong and acquired PE appears to be both neurobiogenic and psychogenic. While psychogenic factors appear to be contributory to PE, pharmacologic intervention of PE can modify intravaginal ejaculatory latency time (IELT), which suggests that IELT is a biological variable, and is likely biologically dependent upon neurotransmitters and hormones.

Phosphodiesterase type 5 inhibitors: the day after

OBJECTIVE

Review the literature on phosphodiesterase type 5 inhibitors (PDE5-Is), addressing critical issues in their current and future use, assessing unanswered questions, and identifying research needs.

METHODS

A MEDLINE search was conducted on PDE5-Is, with emphasis on clinical trials and experience, for interpretation and analysis of their present and future role.

RESULTS

Although approximately 40 million patients with erectile dysfunction have been treated successfully worldwide with the three available PDE5-Is, inappropriate instructions, lack of follow-up, and lack of patient-centered care models are the main reasons for "non-response," leading to drop-out rates of >50%. Patients with severe neurologic damage, diabetes mellitus, or severe vascular disease may be resistant to PDE5-Is. Preservation of corporal smooth muscle with chronic administration of PDE5-Is has been reported and substantial evidence indicates that these drugs have beneficial effects on endothelium and cardiovascular function; sildenafil has been approved for the treatment of idiopathic pulmonary hypertension. Improvement of lower urinary tract symptoms in men with benign prostatic hyperplasia after PDE5-I administration has been also suggested.

CONCLUSIONS

The data indicate the necessity for (1) exploration of the pharmacologic characteristics of the three PDE5-Is; (2) research on their pharmacologic differences because some actions seems to be drug-specific; (3) development of alternative management strategies, such as chronic, low, everyday doses of PDE5-Is, if the monthly cost is affordable; and (4) clinical trials on use of PDE5-Is to treat other chronic conditions. The door for innovative therapeutic approaches will open, specifically for cross-risk factor treatment with PDE5-Is or their use in combination treatments or new multimodal pills that take advantage of drugs that exert pleiotropic vascular actions.

Prevalence, characteristics and implications of premature ejaculation/rapid ejaculation

PURPOSE

Premature ejaculation/rapid ejaculation is a common but incompletely understood male sexual dysfunction. The purposes of this review are to 1) raise awareness of the prevalence and characteristics of PE/RE, its impact on the male and his partner, and the lack of approved medications indicated for its treatment, 2) encourage dialogue about PE/RE between physicians and patients, and 3) stimulate the development of appropriate new therapies.

MATERIALS AND METHODS

A MEDLINE search was performed to retrieve articles relating to PE/RE pathophysiology, etiology, impact, diagnosis and treatment. Sexual medicine journals not indexed in MEDLINE, sexual medicine texts and congress abstracts were also reviewed.

RESULTS

No universally accepted definition, licensed treatment, validated screening instrument or diagnostic criteria have been established for PE/RE, and its pathophysiology and etiology are incompletely understood. Additional barriers are the reluctance of patients and physicians to talk about PE/RE and the lack of knowledge regarding available treatments. Current pharmacological treatments include off label uses of antidepressants, topical anesthetics or phosphodiesterase-5 inhibitors. All are associated with drawbacks that limit their efficacy. Psychological counseling and behavioral therapy have a valuable role, although resources for this modality are limited.

CONCLUSIONS

Prevalence rates of 20% to 30% and negative effects on the quality of life of men and their partners illustrate the need for improved, standardized methods of PE/RE diagnosis, assessment and treatment. Medications indicated specifically for PE/RE and effective on an as needed basis are required. Behavioral therapies should emphasize pleasure, arousal, control, confidence and satisfaction, and they may have the best success when coupled with pharmacological approaches.

Premature ejaculation: the current literature

PURPOSE OF REVIEW

The recent increase in research with regard to premature ejaculation has led to a significant number of new papers looking at the diagnosis, definition, aetiology and management of this condition.

RECENT FINDINGS

The intravaginal ejaculatory latency time remains the primary measure of ejaculatory time although increasing bother and distress require assessment and establishment of quantifiable measures. Biological and psychogenic causes contribute to a multifactorial model of premature ejaculation with some neurobiological vulnerability. The principal treatments are selective serotonin reuptake inhibitors and behavioural cognitive interventions. New treatment interventions are under investigation.

SUMMARY

A number of guideline papers confirm that a primary sexual history and a multimodel treatment approach provide the best approach to patients with this common condition.

Possible role of sildenafil in inhibiting rat vas deferens contractions by influencing the purinergic system

AIM

To evaluate the effect of sildenafil, a selective inhibitor of cyclic guanosine monophosphate (cGMP)-selective type 5 phosphodiesterase, on isolated rat vas deferens and its connections with the purinergic system.

METHODS

Epididymal and prostatic portions of isolated vas deferens were placed in organ baths containing Krebs' solution. Contractions were induced by noradrenaline (NA), adenosine triphosphate (ATP), alpha,beta-methylene ATP and electrical field stimulation (EFS). The effect of sildenafil on the contractions was compared with suramin and Evans blue (EB).

RESULTS

NA, ATP, alpha,beta-methylene ATP and EFS caused contractions in both portions of vas deferens. NA-induced contractions were unaffected by sildenafil and suramin but potentiated by EB. ATP-induced contractions were non-competitively inhibited in both portions by sildenafil and suramin but potentiated by EB. alpha,beta-methylene ATP-induced contractions were unaffected by sildenafil but were inhibited in both portions by suramin and EB. EFS-induced contractions were inhibited by sildenafil and suramin while potentiated by EB.

CONCLUSION

Sildenafil inhibited the contractions in both portions of vas deferens, as did suramin. We have suggested that purinergic system has a role in this antagonism and it seems to be mediated by an ATP-dependent mechanism instead of a receptor interaction.

Understanding the structure–activity and structure–selectivity correlation of cyclic guanine derivatives as phosphodiesterase-5 inhibitors by molecular docking, CoMFA and CoMSIA analyses

Molecular docking and 3D-QSAR analyses were performed to understand how PDE5 and PDE6 interact with a series of (49) cyclic guanine derivatives. Using the conformations of the compounds revealed by molecular docking, CoMFA and CoMSIA analyses resulted in the first quantitative structure-activity relationship (QSAR) and first quantitative structure-selectivity relationship (QSSR) models (with high cross-validated correlation coefficient q(2) and conventional correlation coefficient r(2) values) for predicting the inhibitory activity against PDE5 and the selectivity against PDE6. The high q(2) and r(2) values, along with further testing, indicate that the obtained 3D-QSAR and 3D-QSSR models will be valuable in predicting both the inhibitory activity and selectivity of cyclic guanine derivatives for these protein targets. A set of 3D contour plots drawn based on the 3D-QSAR and 3D-QSSR models reveal some useful clues to improve both the activity and selectivity by modifying structures of the compounds. It has been demonstrated that both the steric and electrostatic factors should appropriately be taken into account in future rational design and development of more active and more selective PDE5 inhibitors for the therapeutic treatment of erectile dysfunction (ED).

Comparison of efficacy of sildenafil-only, sildenafil plus topical EMLA cream, and topical EMLA-cream-only in treatment of premature ejaculation

OBJECTIVES

To compare the efficacy of sildenafil (Viagra) only, sildenafil plus topical anesthetic cream (EMLA), and topical EMLA-cream-only to that of placebo in treating premature ejaculation.

METHODS

A total of 84 patients were enrolled in this study. The duration of premature ejaculation in the patients ranged from 9 to 60 months (mean 32.5 +/- 14.6). Patients were randomized into four groups. Group 1 consisted of 20 patients who took placebo for 2 months. Groups 2 and 3 consisted of 20 and 22 patients, respectively, and they received 50 mg sildenafil 45 minutes before coitus for 2 months. In addition, patients in group 3 applied topical EMLA cream to the glans penis 15 minutes before coitus. The 22 patients in group 4 used topical EMLA-cream-only. After at least eight sexual attempts, the patients' clinical responses were assessed using the patient self-description method. Effectiveness was described as improvement plus cure.

RESULTS

The effectiveness was 40% in group 1, 55% in group 2, 86.4% in group 3, and 77.3% in group 4. Of the groups, a significant difference was found in the effectiveness of the treatments (Pearson chi-square= 0.00). No significant difference was found between groups 1 and 2 (P = 0.26). Efficacy was more successful in groups 3 and 4 than in the others (P = 0.00). The difference between groups 3 and 4 was not significant (Pearson chi-square = 0.42).

CONCLUSIONS

Sildenafil-only was not superior to placebo or combination treatment. Topical EMLA-cream-only had equal effectiveness to that of sildenafil plus topical EMLA treatment. The use of topical EMLA-cream-only seems to be an effective treatment of premature ejaculation.

Correlation between ejaculatory and erectile dysfunction

Summary Premature ejaculation (PE) and erectile dysfunction (ED) are different sexological issues. However, they have many little-known links. PE is the most common male sexual dysfunction, but ED is undoubtedly the most common reason that medical help is sought. As a consequence, PE is largely under-diagnosed and under-treated, while ED has received great scientific and clinical attention in recent years. There are plenty of reasons for this: (i) PE is classically considered as psychogenic in nature; (ii) it is traditionally treated with behavioural psychotherapies; (iii) clear and accepted clinical definition(s) are lacking; (iv) the aetiologies are largely unknown; (v) the pathogenesis is still obscure - there is a lack of awareness and acknowledgement of PE as a symptom of medical disease; (vi) lacking a medical presence in the field and requests for help from patients are low. Finally, erectile dysfunctions (ED) and ejaculatory dysfunctions frequently overlap. The aim of this review article is to propose a new taxonomy of PE, which considers ED as an important factor of PE and vice versa.

Can smooth muscle represent a useful target for the treatment of rapid ejaculation?

Rapid ejaculation is probably the most common form of male sexual dysfunction. Current research into the treatment of the condition has focused on centrally acting or topical desensitizing agents; however, no treatment has yet been approved. An alternative approach could be to develop drugs that act directly upon the target organ itself and our increasing knowledge of the molecular biology of the accessory sex organs makes this a realistic possibility. This review analyzes the information in the literature that would support such a hypothesis. Particular emphasis has been placed on articles that have investigated smooth muscle cell relaxation. A critical review of the literature has revealed that there are potentially a myriad of targets through which rapid ejaculation can be treated.