Therapeutic targets for premature ejaculation

Ejaculatory dysfunction in men with diabetes mellitus

Diabetes mellitus (DM) is a metabolic disorder that is characterized by elevated blood glucose levels due to absolute or relative insulin deficiency, in the background of β-cell dysfunction, insulin resistance, or both. Such chronic hyperglycemia is linked to long-term damage to blood vessels, nerves, and various organs. Currently, the worldwide burden of DM and its complications is in increase. Male sexual dysfunction is one of the famous complications of DM, including abnormal orgasmic/ejaculatory functions, desire/libido, and erection. Ejaculatory dysfunction encompasses several disorders related to DM and its complications, such as premature ejaculation, anejaculation (AE), delayed ejaculation, retrograde ejaculation (RE), ejaculatory pain, anesthetic ejaculation, decreased ejaculate volume, and decreased force of ejaculation. The problems linked to ejaculatory dysfunction may extend beyond the poor quality of life in diabetics as both AE and RE are alleged to alter the fertility potential of these patients. However, although both diabetes patients and their physicians are increasingly aware of diabetic ejaculatory dysfunction, this awareness still lags behind that of other diabetes complications. Therefore, all these disorders should be looked for thoroughly during the clinical evaluation of diabetic men. Besides, introducing the suitable option and/or maneuvers to treat these disorders should be tailored according to each case. This review aimed to explore the most important findings regarding ejaculatory dysfunction in diabetes from pre-clinical and clinical perspectives.

Spontaneous Ejaculation: A Focused Review for the Clinicians

INTRODUCTION

The process of ejaculation has important meanings not only for its association with orgasm but also for the timing to ejaculate in the context of sexual activity. Spontaneous (involuntary) ejaculation (SE) without any sexual stimulation is a distressing symptom. Our understanding of SE is limited. Unfortunately, many physicians are not aware of these cases.

OBJECTIVES

The objective of this study is to describe the etiopathogenesis, clinical features, diagnosis, and treatment options for SE.

METHODS

We searched the literature for publications on "SE," "spontaneous emission" or "involuntary ejaculation," and factors influencing SE in the PUBMED/MEDLINE, Scopus, Cochrane Library, EMBASE, PsycINFO, ProQuest, Academic Search Complete database, Google Scholar, and CINAHL databases from inception to August 2020.

RESULTS

The literature search yielded 36 relevant publications reporting on 43 patients with SE. Attempts to explain the cause of pathologic SE have included 4 etiological groups (spinal cord lesions, psychological causes, rabies, and drug-induced). The underlying mechanisms responsible for induction of SE may include increased adrenergic activity, overactivity in dopaminergic system, decreased serotonergic activity, damage of descending inhibitory pathway, or penile hyperexcitability. SE may occur in the absence of an identifiable trigger or may be triggered by non-sexual circumstances (micturition, defecation, glans touch, anxiety, panic attack, or school examinations). Treatment options include psychoanalytic treatment, paroxetine, citalopram, sertraline, silodosin, and anxiolytics. In drug-induced SE, dose reduction and drug withdrawal with or without switching to another drug may relief SE.

CONCLUSIONS

SE is one of the least reported ejaculatory dysfunction. The key feature shared in common by these men is SE without any sexual thoughts or fantasies, may be triggered by non-sexual contexts, rarely associated with orgasm or erection. Treatment by psychoanalytic treatment and pharmacotherapy may be helpful. Further research might explore the definite underlying mechanisms. Abdel-Hamid IA, Ali OI. Spontaneous Ejaculation: A Focused Review for the Clinicians. Sex Med Rev 2021;9:406-422.

Revisiting the Pharmacodynamic Uroselectivity of α 1-Adrenergic Receptor Antagonists

α₁-Adrenoceptor (AR) antagonists are widely used for the relief of urinary retention secondary to benign prostatic hyperplasia (BPH). While the five Food and Drug Administration-approved α ₁-AR antagonists (terazosin, doxazosin, alfuzosin, tamsulosin, and silodosin) share similar efficacy, they differ in tolerability, with reports of ejaculatory dysfunction. The aim of the present work was to revisit their α ₁-AR subtype selectivity as well as of LDT5 (1-(2-methoxyphenyl)-4-[2-(3,4-dimethoxyphenyl) ethyl]piperazine monohydrochloride), a compound previously described as a multitarget antagonist of α _1A-/α _1D-AR and 5-HT_1A receptors, and to estimate their affinity for D₂, D₃, and 5-HT_1A receptors, which are putatively involved in ejaculatory dysfunction. Competition binding assays were performed with native (D₂, 5-HT_1A) or transfected (human α _1A-, α _1B-, α _1Dt-AR, and D₃) receptors for determination of the drug's affinities. Tamsulosin and silodosin have the highest affinities for α _1A-AR, but only silodosin is clearly a selective α _1A-AR antagonist, with K _i ratios of 25.3 and 50.2 for the α _1D- and α _1B-AR, respectively. Tamsulosin, silodosin, and LDT5 (but not terazosin, doxazosin, and alfuzosin) have high affinity for the 5-HT_1A receptor (K _i around 5-10 nM), behaving as antagonists. We conclude that the uroselectivity of tamsulosin is not explained by its too-low selectivity for the α _1A- versus α _1B-AR, and that its affinity for D₂ and D₃ receptors is probably too low for explaining the ejaculatory dysfunction reported for this drug. Present data also support the design of "better-than-LDT5" new multitarget lead compounds with pharmacokinetic selectivity based on poor brain penetration and that could prevent hyperplastic cell proliferation and BPH progression. SIGNIFICANCE STATEMENT: The present work revisits the uroselectivity of the five Food and Drug Administration-approved α₁ adrenoceptor antagonists for the treatment of benign prostatic hyperplasia (BPH). Contrary to what has been claimed by some, our results indicate that the uroselectivity of tamsulosin is probably not fully explained by its too-weak selectivity for the α_1A versus α_1B adrenoceptors. We also show that tamsulosin affinity for D₃ and 5-HT_1A receptors is probably too low for explaining the ejaculatory dysfunction reported for this drug. Based on our lead compound LDT5, present data support the search for a multitarget antagonist of α_1A-α_1D and 5-HT_1A receptors with poor brain penetration as an alternative for BPH treatment.

Preliminary Evidence for an Association Between Variants of the Catechol-O-Methyltransferase (COMT) Gene and Premature Ejaculation

BACKGROUND

Studies have suggested that dopamine plays a role in the neurobiological mechanism that triggers ejaculation, leading scientists to hypothesize that dopamine-related genetic polymorphisms could contribute to symptoms of premature ejaculation (PE).

AIM

To investigate associations between dopamine receptor and catechol-O-methyltransferase (COMT; an enzyme involved in the catabolism of dopamine) gene-linked polymorphisms and PE.

METHODS

PE status in patient groups was determined by clinical diagnosis performed by a physician specializing in sexual medicine. Self-reported PE symptoms from a validated questionnaire also were reported. Saliva samples were collected from 149 patients with PE and 1,022 controls from a population-based sample. In total, we tested associations between PE and 11 single-nucleotide polymorphisms in the dopamine receptor D1, D2, and D3 genes and in the COMT gene.

OUTCOMES

We found no associations between dopamine receptor gene polymorphisms and PE, but 2 COMT-linked loci (rs4680 and rs4818) had significant associations after correction for multiple testing.

RESULTS

1 COMT gene-linked locus that was associated with PE symptoms in the present study, rs4680, is a well-documented functional polymorphism that causes a valine-to-methionine substitution. The other polymorphism, rs4818, is in high linkage disequilibrium with the rs4680 locus, indicating that they capture the same effect. Surprisingly, the rs4680 variant that was statistically significantly more prevalent in the PE group (ie, the valine-encoding allele) has been associated with higher enzymatic activity and therefore lower synaptic dopamine levels.

CLINICAL TRANSLATION

Drugs targeting the dopaminergic system could affect PE symptoms.

STRENGTHS AND LIMITATIONS

No replication sample was available for the present study; thus, our findings should be interpreted with caution. Moreover, a limitation of our study is the small sample in the context of genetic association studies (although it should be mentioned that genetically informative samples with phenotypic information about PE symptoms are scarce, and most previous genetic association studies of PE have used samples of similar or smaller size). However, our results are plausible: we report an association between one of the most extensively studied and understood genetic polymorphisms in psychiatric research and PE, and our results are in line with the long-standing hypothesis that dopamine influences human ejaculatory function.

CONCLUSIONS

We report an association between 2 COMT gene-linked loci and PE symptoms, but our results should be treated with caution until independently replicated. Jern P, Johansson A, Strohmaier J, et al. Preliminary Evidence for an Association Between Variants of the Catechol-O-Methyltransferase (COMT) Gene and Premature Ejaculation. J Sex Med 2017;14:1558-1565.

Discontinuation of Dapoxetine Treatment in Patients With Premature Ejaculation: A 2-Year Prospective Observational Study

Introduction

Although dapoxetine is the only oral pharmacologic agent approved for the treatment of premature ejaculation (PE) and is very effective, the discontinuation rate is high.

Aim

To assess the discontinuation rate of patients with PE and the reasons for discontinuation in real-world practice.

Methods

In total, 182 consecutive patients were enrolled. Type of PE, self-estimated intravaginal ejaculation latency time, and medical history were evaluated in all patients who also completed the erectile function domain of the International Index of Erectile Function (IIEF). Visits were scheduled 1, 3, 6, 12, and 24 months after initiation of therapy; treatment status and the reasons for discontinuation in those who did discontinue were checked. The relations of discontinuation rates were compared with various parameters and the time to discontinuation after treatment commencement.

Results

Of all patients, 9.9% continued treatment to 2 years. The cumulative discontinuation rates at 1, 3, 6, 12, and 24 months were 26.4%, 61.6%, 79.1%, 87.3%, and 90.1%, respectively. Moreover, 79.1% of all patients discontinued treatment within 6 months. After 12 months, the discontinuation rate decreased sharply. The reasons for discontinuation were cost (29.9%), disappointment that PE was not curable and that dapoxetine was required every time sexual intercourse was contemplated (25%), side effects (11.6%), perceived poor efficacy (9.8%), a search for other treatment options (5.5%), and unknown (18.3%). Patients with acquired PE (vs lifelong PE), with intravaginal ejaculation latency time longer than 2 minutes before treatment, on phosphodiesterase type 5 inhibitors, and with IIEF erectile function scores lower than 26 tended to discontinue early and thus exhibited high dropout rates.

Conclusion

The treatment discontinuation rate of dapoxetine was very high. The main reasons for discontinuation were the cost and disappointment that treatment was required every time adequate sexual function was required.

Park HJ, Park NC, Kim TN, et al. Discontinuation of Dapoxetine Treatment in Patients With Premature Ejaculation: A 2-Year Prospective Observational Study. Sex Med 2017;5:e99–e105.

Mondia whitei (Periplocaceae) prevents and Guibourtia tessmannii (Caesalpiniaceae) facilitates fictive ejaculation in spinal male rats

Background

Mondia whitei and Guibourtia tessmannii are used in Cameroon traditional medicine as aphrodisiacs. The present study was undertaken to evaluate the pro-ejaculatory effects of the aqueous and organic solvent extracts of these plants in spinal male rats.

Methods

In spinal cord transected and urethane-anesthetized rats, two electrodes where inserted into the bulbospongiosus muscles and the ejaculatory motor pattern was recorded on a polygraph after urethral and penile stimulations, intravenous injection of saline (0.1 ml/100 g), dopamine (0.1 μM/kg), aqueous and organic solvent plant extracts (20 mg/kg).

Results

In all spinal rats, urethral and penile stimulations always induced the ejaculatory motor pattern. Aqueous or hexane extract of Mondia whitei (20 mg/kg) prevented the expression of the ejaculatory motor pattern. The pro-ejaculatory effects of dopamine (0.1 μM/kg) were not abolished in spinal rats pre-treated with Mondia whitei extracts. Aqueous and methanolic stem bark extracts of Guibourtia tessmannii (20 mg/kg) induced fictive ejaculation characterized by rhythmic contractions of the bulbospongiosus muscles followed sometimes with expulsion of seminal plugs. In rats pre-treated with haloperidol (0.26 μM/kg), no ejaculatory motor pattern was recorded after intravenous injection of Guibourtia tessmannii extracts (20 mg/kg).

Conclusion

These results show that Mondia whitei possesses preventive effects on the expression of fictive ejaculation in spinal male rats, which is not mediated through dopaminergic pathway; on the contrary, the pro-ejaculatory activities of Guibourtia tessmannii require the integrity of dopaminergic system to exert its effects. The present findings further justify the ethno-medicinal claims of Mondia whitei and Guibourtia tessmannii.

Polymorphic variants of neurotransmitter receptor genes may affect sexual function in aging males: data from the HALS study

BACKGROUND/AIMS

Human behavior is influenced by a number of brain neurotransmitters. Central dopamine, serotonin and melanocortin systems have special importance for male sexual function. We searched for associations between male aging symptoms and polymorphic sites of serotonin (5-HTR1B), melanocortin (MC4R) and dopamine (DRD2, DRD4) receptors.

METHODS

In a population-based sample, genotyping of 5-HTR1B (polymorphism: G861C), MC4R (polymorphisms: C-2745T, Val103Ile), DRD2 (polymorphism: C313T) and DRD4 (polymorphism: 48-bp VNTR) was performed in 387 healthy men. The Aging Males' Symptoms (AMS) scale was used to evaluate specific ailments of aging men. We analyzed answers to questions from the AMS scale. Five points of the questionnaire addressed sexual symptoms of the aging male: feeling of passing one's peak, decrease in beard growth, decrease in ability/frequency to perform sexually, decrease in the number of morning erections, and decrease in sexual desire/libido (lacking pleasure in sex, lacking desire for sexual intercourse). Relations between reported symptoms and variants of the polymorphic sites of the studied genes were assessed.

RESULTS

After adjusting for confounding factors (education, arterial hypertension, physical activity, weight, waist circumference) an association between the sexual dimension of AMS and genetic variants of 5-HTR1B G861C (p = 0.04) was observed.

CONCLUSIONS

Variability of neurotransmitter receptor genes may be associated with sexual symptoms of aging in men.

[Rehabilitation for intravaginal ejaculatory dysfunction with using a masturbation aid]

OBJECTIVES

Recently the incidence of intravaginal ejaculatory dysfunction is increasing among infertile couples in Japan. Some unusual ways of masturbation and psychogenic issues were reported to cause this disorder. Patients, who had done masturbation in an unusual way for long time since their adolescence, were difficult to gain normal intravaginal ejaculation by the behavior therapy which was used for erectile dysfunction. We, therefore, used a masturbation aid (TENGA) for rehabilitation of ejaculation to overcome this condition.

PATIENTS AND METHODS

From January, 2010 through March, 2011, a total of 16 patients with intravaginal ejaculatory dysfunction underwent rehabilitation of ejaculation using TENGA. Patients' satisfaction and achievement of intravaginal ejaculation were evaluated by the questionnaire.

RESULTS

Twelve patients (75%) could ejaculate in the masturbation aid (TENGA). Five patients (31%) succeeded to ejaculate in the partner's vagina after rehabilitation.

CONCLUSIONS

A masturbation aid (TENGA) was a useful tool to correct the way of masturbation and achieve normal intravaginal ejaculation. This masturbation aid can be one of the effective options for the treatment of intravaginal ejaculatory dysfunction.

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.