Effects of ??1-Adrenoceptor Antagonists on Male Sexual Function

[Medical therapy of lower urinary tract symptoms [corrected]]

Male lower urinary tract symptoms (LUTS) include storage and voiding disorders and should be carefully evaluated before the start of any treatment. Medical therapy is directed at improving symptoms and reducing the risk of progression in order to improve quality of life and prevent complications, such as acute urinary retention, or the need for surgical intervention. Careful assessment of the individual complaints helps to identify the best drug which should be adapted to each individual patient's risk profile. At present, α(1)-adrenoreceptor inhibitors and 5-alpha reductase inhibitors and their combination form the gold standard for pharmacological treatment. In addition, anticholinergic agents are increasingly being used as monotherapy or in combination with α1-adrenocepetor inhibitors for patients with predominant storage disorders while phosphodiesterase 5 (PDE5) inhibitors may be suitable for patients suffering from LUTS and concomitant erectile dysfunction.

Assessment of tamsulosin as a potential male contraceptive in healthy volunteers

OBJECTIVE

To investigate the efficacy and safety of tamsulosin, an α(1A)-adrenoceptor antagonist, as a potential male contraceptive.

METHODS

Forty healthy male volunteers were equally divided into 2 groups, each of which received placebo and tamsulosin sequentially in a crossover manner. Ejaculatory profile was examined 4 to 6 hours after administration and adverse effects were noted.

RESULTS

Anejaculation occurred in all subjects after taking 0.8-mg of tamsulosin. Total functional sperm count was significantly reduced in subjects after taking 0.4-mg of tamsulosin. Six subjects receiving 0.8-mg of tamsulosin complained of tolerated discomfort, which disappeared 10 hours after administration.

CONCLUSION

When administered at 0.8 mg, tamsulosin can cause anejaculation with some transient side effects. Our results imply that tamsulosin and related drugs might potentially be used as male contraceptive agents in the future, which needs more studies to verify.

Tadalafil 2.5 or 5 mg administered once daily for 12 weeks in men with both erectile dysfunction and signs and symptoms of benign prostatic hyperplasia: results of a randomized, placebo-controlled, double-blind study

INTRODUCTION

Erectile dysfunction (ED) and lower urinary tract symptoms suggestive of benign prostatic hyperplasia (BPH-LUTS) commonly coexist in aging men. Tadalafil, a phosphodiesterase type 5 inhibitor approved for treating ED, is currently being evaluated for treating BPH-LUTS.

AIMS

This multinational Phase 3 study assessed effects of tadalafil 2.5 or 5 mg once daily on ED and BPH-LUTS in men with both conditions during 12 weeks of double-blinded therapy.

METHODS

Men were ≥ 45 years old, sexually active, and experiencing ED for ≥ 3 months and BPH-LUTS for >6 months. Randomization (baseline) followed a 4-week placebo lead-in; changes from baseline were assessed via analysis of covariance and compared to placebo. A gatekeeping procedure controlled for multiple comparisons of co-primary and key secondary measures at end point (last post-baseline observation).

MAIN OUTCOME MEASURES

The co-primary measures were the International Index of Erectile Function-erectile function (IIEF-EF) domain and International Prostate Symptom Score (IPSS) score; key secondary measures were the Sexual Encounter Profile Question 3 (SEP Q3) and BPH Impact Index (BII). Treatment-emergent adverse events, serious adverse events, orthostatic vital signs, clinical laboratory and uroflowmetry parameters, and postvoid residual volume were assessed.

RESULTS

Tadalafil 2.5 mg (N = 198) and 5 mg (N = 208) significantly improved IIEF-EF domain scores (both P < 0.001) vs. placebo (N = 200) at end point. For IPSS, improvements were significant with tadalafil 5 mg (P < 0.001), but not 2.5 mg, for observations from 2 weeks through end point (least-squares mean ± standard error change from baseline at end point, placebo -3.8 ± 0.5, tadalafil 2.5 mg -4.6 ± 0.4, and 5 mg -6.1 ± 0.4). Tadalafil 5 mg significantly improved SEP Q3 and BII (P < 0.001). Overall, tadalafil was well tolerated with no clinically adverse changes in orthostatic vital signs or uroflowmetry parameters.

CONCLUSIONS

Tadalafil 5 mg significantly improved both ED and BPH-related outcomes through 12 weeks and was well tolerated.

Effect of tamsulosin on ejaculatory function in BPH/LUTS

This study was undertaken to determine the impact on ejaculatory function of tamsulosin (0.2 mg) given once daily (OD) for 12 weeks and to identify risk factors for ejaculatory dysfunction in patients undergoing this treatment. Males with an International Prostatic Symptom Score (IPSS) ≥8 were enrolled in this study. All participants completed questionnaires, including the IPSS and the Male Sexual Health Questionnaire (MSHQ), and serum prostate-specific antigen, transrectal ultrasound and uroflowmetry with post-void residual were measured. After initiating 0.2 mg OD tamsulosin, patients were re-evaluated on the fourth and twelfth weeks of medication. The chi-squared test, the independent t-test and one-way ANOVA were used to compare means. Binary logistic regression analysis was used to calculate the odds ratio for all risk factors. A total of 177 men constituted the study cohort. No significant difference was observed between baseline and follow-up for the erectile function, ejaculatory function, satisfaction, sexual activity and desire domains (EFD, EjFD, SDA and ADD) or for erectile or ejaculatory bother mean scores. After 12 weeks, the overall incidence of ejaculatory dysfunction (EjD) was 13.4%. Incidences of the seven different types of EjD (decreased frequency, delay, dryness, decreased strength/force, decreased volume, decreased pleasure and pain at ejaculation) were 2.4%, 3.1%, 3.9%, 3.9%, 6.3%, 7.1% and 3.1%, respectively. Baseline EjFD scores were higher for IPSS responders than for non-responders (26.09 vs. 24.06, P=0.03). An EjFD score reduction was more frequent in IPSS responders. The incidence of EjD was small, but not negligible and was more frequent in patients with less lower urinary tract symptoms, a smaller prostate, higher baseline MSHQ totals and higher EjFD scores.

Tamsulosin oral controlled absorption system (OCAS) in the treatment of benign prostatic hypertrophy

The efficacy of tamsulosin at the cost of a relatively benign side effect profile has been attributed to receptor selectivity directed at the α_1a and α_1d adrenergic receptor subtypes. The oral-controlled absorption system (OCAS^®) represents a drug delivery refinement that incorporates a matrix of gel-forming and gel-enhancing agents to promote a constant drug release independent of environmental food or fluid. There are clinical data to support the concept that drug peaks are lessened and that drug release continues throughout the alimentary tract due to the OCAS formulation. Furthermore this equates with less adverse effects on physiologic parameters. To date however improvements in cardiovascular symptoms such as dizziness, headache and syncope have not been demonstrated in healthy men. Ejaculatory dysfunction appears less problematic with the OCAS preparation. Tamsulosin OCAS may be of greatest benefit to men with cardiovascular co-morbidities taking anti-hypertensive medications that might predispose them to symptomatic hypotensive episodes. It will be necessary to evaluate this group of men more closely in further trials to determine what they stand to gain from changing medications, and then relate this to drug costs to draw a final conclusion as to the place of tamsulosin OCAS in contemporary urological practice.

The forefront for novel therapeutic agents based on the pathophysiology of lower urinary tract dysfunction: alpha-blockers in the treatment of male voiding dysfunction - how do they work and why do they differ in tolerability?

alpha(1)-Adrenoceptor antagonists are the mainstay of medical treatment of male voiding dysfunction which typically is attributed to benign prostatic hyperplasia. While original concepts have assumed that they relieve voiding dysfunction by relaxing prostatic smooth muscle, newer data indicate that their therapeutic effects at least partly occur independent of prostatic relaxation, perhaps involving direct effects on blood vessels, urothelium, afferent nerves, and/or smooth muscle of the urinary bladder. The adverse event profiles differ among alpha(1)-adrenoceptor antagonists, with tamsulosin having a particularly good cardiovascular tolerability. While this was originally attributed to its selectivity for alpha(1A)-adrenoceptors, it appears that alfuzosin which lacks subtype-selectivity, has a very similar tolerability. In contrast, doxazosin and terazosin, which are chemically and pharmacologically more closely related to alfuzosin than to tamsulosin, appear to have more side effects attributable to the cardiovascular system. More recent data indicate that tolerability differences between alpha(1)-adrenoceptor antagonists may at least partly relate to pharmacokinetic rather than to pharmacodynamic differences. Taken together, these data emphasize the idea that concepts about drug efficacy and tolerability despite being highly plausible may not necessarily be true and always require thorough experimental testing.

Expression and function of G-protein-coupled receptorsin the male reproductive tract

This review focuses on the expression and function of muscarinic acetylcholine receptors (mAChRs), α1-adrenoceptors and relaxin receptors in the male reproductive tract. The localization and differential expression of mAChR and α1-adrenoceptor subtypes in specific compartments of the efferent ductules, epididymis, vas deferens, seminal vesicle and prostate of various species indicate a role for these receptors in the modulation of luminal fluid composition and smooth muscle contraction, including effects on male fertility. Furthermore, the activation of mAChRs induces transactivation of the epidermal growth factor receptor (EGFR) and the Sertoli cell proliferation. The relaxin receptors are present in the testis, RXFP1 in elongated spermatids and Sertoli cells from rat, and RXFP2 in Leydig and germ cells from rat and human, suggesting a role for these receptors in the spermatogenic process. The localization of both receptors in the apical portion of epithelial cells and smooth muscle layers of the vas deferens suggests an involvement of these receptors in the contraction and regulation of secretion.

[Why and how to assess hypospermia?]

Hypospermia is a semen volume lower than 2 mL on at least two semen analyses. The etiologies of hypospermia are many and may be divided into two pathophysiologic sub-groups: disturbances of ejaculation reflex leading to partial retrograde ejaculation and seminal glands and ducts anatomic and functional anomalies. In this last pathologic mechanism, the mutations of CFTR gene, involved in many different forms of cystic fibrosis, represent a possible cause of hypospermia. The molecular anomaly of CFTR gene's screening is very important for the potential descendents and for the patient himself. It must be considered any time clinic and/or paraclinic context is evocative.

Immunolocalization of alpha(1A)-adrenoceptors in rat and human epididymis

Immunohistochemistry was conducted to analyze the cellular localization of alpha(1A)-adrenoceptors along rat and human epididymis. ADR-A, a polyclonal antibody that recognizes the specific C-terminal region of alpha(1A)-adrenoceptors, immunostained this adrenoceptor subtype in smooth muscle cells surrounding the epididymal tubules and interstitial blood vessels and in subpopulations of epithelial cells from adult rat and human caput and cauda epididymidis. The same cell types from rat epididymidis were immunostained by ADR-1, a polyclonal antibody that recognizes a common region of the three alpha(1)-adrenoceptor subtypes, alpha(1A), alpha(1B), and alpha(1D). Immunostaining with both antibodies was also conducted in adult rat and human vas deferens and seminal vesicle used as positive controls because of the abundance of alpha(1A)-adrenoceptors in these tissues. ADR-A- and ADR-1-positive immunostaining was differentially distributed depending on the antibody, method of tissue fixation (Bouin-fixed and fresh frozen tissues), species (rat and human), tissue (caput and cauda epididymidis), and age (immature and adult rats) analyzed. This is the first report immunolocalizing alpha(1A)-adrenoceptor along rat and human epididymis. The presence of this adrenoceptor subtype in epididymal smooth muscle and epithelial cells indicates their contribution to smooth muscle contractile responses and a possible role in the absorptive and/or secretory activities of the epithelium lining the epididymal duct. Taken together, our results should contribute to a better understanding of the physiological role of alpha(1)-adrenoceptors in the epididymidis and the importance of the sympathetic nervous system for male (in)fertility.

Alpha1-adrenoceptors are required for normal male sexual function

BACKGROUND AND PURPOSE

Alpha(1)-adrenoceptor antagonists are extensively used in the treatment of hypertension and lower urinary tract symptoms associated with benign prostatic hyperplasia. Among the side effects, ejaculatory dysfunction occurs more frequently with drugs that are relatively selective for alpha(1A)-adrenoceptors compared with other drugs of this class. This suggests that alpha(1A)-adrenoceptors may contribute to ejaculation. However, this has not been studied at the molecular level.

EXPERIMENTAL APPROACH

The physiological contribution of each alpha(1)-adrenoceptor subtype was characterized using alpha(1)-adrenoceptor subtype-selective knockout (KO) mice (alpha(1A)-, alpha(1B)- and alpha(1D)-AR KO mice) since the subtype-specific drugs available are only moderately selective. We analysed the role of alpha(1)-adrenoceptors in the blood pressure and vascular response as well as ejaculation by determining these variables in alpha(1)-adrenoceptor subtype-selective KO mice and in mice with all their alpha(1)-adrenoceptor subtypes deleted (alpha(1)-AR triple-KO mice).

KEY RESULTS

The pregnancy rate was reduced by 50% in alpha(1A)-adrenoceptor KO mice, and this reduction was dramatically enhanced in alpha(1)-adrenoceptor triple-KO mice. Contractile tension of the vas deferens in response to noradrenaline was markedly decreased in alpha(1A)-adrenoceptor KO mice, and this contraction was completely abolished in alpha(1)-adrenoceptor triple-KO mice. This attenuation of contractility was also observed in the electrically stimulated vas deferens.

CONCLUSIONS AND IMPLICATIONS

These results demonstrate that alpha(1)-adrenoceptors, particularly alpha(1A)-adrenoceptors, are required for normal contractility of the vas deferens and consequent sperm ejaculation as well as having a function in fertility.

Alpha1-adrenoceptors and ejaculatory function

The abnormal ejaculation of semen is a typical but infrequent side effect of some alpha(1)-adrenoceptor antagonists, particularly those with selectivity for alpha(1A)-adrenoceptors such as silodosin or tamsulosin. Recent clinical studies suggest that this represents a relative anejaculation rather than a retrograde ejaculation. An elegant study in this issue of the journal using alpha(1A) single and alpha(1A/B/D) triple knock-out mice reports a similar phenomenon in rodents. Using a multi-disciplinary approach, the reduced ejaculation and related male infertility is shown to be caused by an impaired function of the vas deferens rather than by alterations in sperm formation, number or function. Similarities and differences between mouse and human data are discussed, particularly why a complete inhibition of all three alpha(1)-adrenoceptor subtypes has the strongest effects in mice whereas apparently only alpha(1A)-adrenoceptor-selective drugs impair ejaculatory function in humans.

Pharmacology of α1-adrenoceptor antagonists in the lower urinary tract and central nervous system

The main use of alpha(1)-adrenoceptor (AR) antagonists in urology has been to treat lower urinary tract symptoms (LUTS) in men with benign prostatic obstruction (BPO). The beneficial effects of these agents are primarily assumed to be because of relaxation of prostatic and urethral smooth muscle. The weak correlation between LUTS and prostatic enlargement, outflow obstruction, or both, however, has refocused interest on the role of extraprostatic alpha-ARs in the pathogenesis of LUTS and their treatment. The alpha(1)-ARs present in the bladder, urethra, vas deferens, peripheral ganglia, nerve terminals, and in the central nervous system could all potentially influence LUTS and, when the receptors are blocked, contribute to both the therapeutic and adverse effects of alpha(1)-AR antagonists. The relevance of alpha(1)-AR-subtype selectivity on the clinical usefulness of existing drug therapies has not been firmly established but it seems that blockade of both alpha(1A/L)- and alpha(1D)-ARs is necessary for the optimum balance between clinical efficacy and adverse effects.

Adverse effects of drug therapies on male and female sexual function

Sexual dysfunctions (SD) are adverse effects of common drug therapies that have rarely been considered in investigations so far. Possibly it is barely known that many widespread and frequently prescribed medications and drug therapies can have significant impact on vascular and nerval processes as well as on endocrinologic and psychoneuroendocrinologic systems and therefore can influence sexual functions. Impotence and disorders of the erectile function can mainly be caused by antidopaminergic mechanisms, whereas ejaculatory disorders and anorgasmia often can be explained by antiserotoninergic effects. Anticholinergic and adrenoloytic agents can also cause a particular impairment of erectile functions. The following considerations will show that the detection and treatment of SD (also in women!) should be given much more attention since drug-induced SDs occur predominantly in indications where a SD itself can be a symptom of the disease.