Alfuzosin, a selective alpha 1-adrenoceptor antagonist in the lower urinary tract

Utilization of absorbance subtraction and ratio difference green spectrophotometric methods for the quantification of alfuzosin hydrochloride and tadalafil in their binary mixture

Alfuzosin hydrochloride and tadalafil fixed-dose combination tablets were recently formulated for the treatment of individuals with lower urinary tract symptoms caused by benign prostatic hyperplasia. Herein, the first spectrophotometric methods for quantitative analysis of alfuzosin hydrochloride and tadalafil in their binary mixture were established. The spectral overlapping of alfuzosin hydrochloride and tadalafil made direct simultaneous analysis unfeasible. Therefore, two mathematical methods were used to solve these overlapping spectra: absorbance subtraction and ratio difference. The absorbance subtraction method manipulates the zero absorption spectra of the studied drugs at the isoabsorptive point (272 nm) and uses the absorbance factor of pure ALF to calculate the absorbance of the studied drugs in the mixture at the isoabsorptive point. The ratio spectra method, on the other hand, manipulates the ratio spectra of the studied drugs, which are obtained by dividing each drug's zero absorption spectra by a divisor spectrum from the second drug. The ratio amplitude difference between 251 nm and 211 nm was directly proportional to alfuzosin hydrochloride, whereas between 292 nm and 222 nm it was directly proportional to tadalafil. The methods used were verified in accordance with the recommendations of the ICH and demonstrated adequate linear regression in working ranges of 1-15 µg/mL for alfuzosin hydrochloride and 3-40 µg/mL for tadalafil. The methods were accurate, precise, and selectively employed to quantify alfuzosin hydrochloride and tadalafil in their combined tablets.

Adrenoceptors in the Lower Urinary Tract

Adrenoceptors importantly contribute to the physiological regulation of lower urinary tract (LUT) function and have become a target of several clinically successful treatments for major LUT diseases. In the bladder dome, β-adrenoceptor subtypes are found in multiple cell types and mediate relaxation of detrusor smooth muscle, perhaps partly indirectly by acting on afferent nerves and cells of the mucosa. β₃-adrenoceptor agonists such as mirabegron and vibegron are used to treat overactive bladder syndrome. In the bladder trigone and urethra, α₁-adrenoceptors cause contraction and thereby physiologically contribute to bladder outlet resistance. α₁-adrenoceptors in the prostate also cause contraction and pathophysiologically elevate bladder outlet resistance leading to voiding dysfunction in benign prostatic hyperplasia. α₁-adrenoceptor antagonist such as tamsulosin is widely used as a first-line option to treat LUT symptoms in men, but it remains unclear to which extent and how smooth muscle relaxation contributes to symptom relief.

A synchronous spectrofluorometric technique for simultaneous detection of alfuzosin and tadalafil: applied to tablets and spiked biological samples

A facile, accurate, eco-friendly and sensitive spectrofluorometric method was evolved to assay alfuzosin hydrochloride (AFH) and tadalafil (TDF) in different matrices. Such a co-administered combination is clinically used for the treatment of lower urinary tract symptoms. Both compounds are characterized by their native fluorescence spectra upon excitation at specific wavelengths. Their characteristic fluorescence spectra were used for sensitive assay of the studied analytes in tablets and human biological samples. The assay principle is based on first-order synchronous spectrofluorometric scan using Δλ = 60 nm in which AFH peaks were recorded at 366 nm. Meanwhile, TDF measurements were recorded at 293 nm in the same scans without overlap with AFH spectra. Recent analytical chemistry trends were implemented to lessen occupational and environmental perils, using ethanol as a diluting solvent for method optimization and application. Linearity ranges were 5.0-90.0 and 10.0-100.0 ng ml^-1 for AFH and TDF, respectively in their raw materials with average % recoveries of 100.44% and 99.73% in raw materials, 100.15% and 100.20% in spiked plasma, and 97.14% and 99.99% in spiked urine. The proposed method was successfully applied to Prostetrol and Starkoprex commercial tablets with no interference with common tablet additives.

A synchronous spectrofluorometric technique for simultaneous detection of alfuzosin and tadalafil: applied to tablets and spiked biological samples

A facile, accurate, eco-friendly and sensitive spectrofluorometric method was evolved to assay alfuzosin hydrochloride (AFH) and tadalafil (TDF) in different matrices. Such a co-administered combination is clinically used for the treatment of lower urinary tract symptoms. Both compounds are characterized by their native fluorescence spectra upon excitation at specific wavelengths. Their characteristic fluorescence spectra were used for sensitive assay of the studied analytes in tablets and human biological samples. The assay principle is based on first-order synchronous spectrofluorometric scan using Δλ = 60 nm in which AFH peaks were recorded at 366 nm. Meanwhile, TDF measurements were recorded at 293 nm in the same scans without overlap with AFH spectra. Recent analytical chemistry trends were implemented to lessen occupational and environmental perils, using ethanol as a diluting solvent for method optimization and application. Linearity ranges were 5.0-90.0 and 10.0-100.0 ng ml^-1 for AFH and TDF, respectively in their raw materials with average % recoveries of 100.44% and 99.73% in raw materials, 100.15% and 100.20% in spiked plasma, and 97.14% and 99.99% in spiked urine. The proposed method was successfully applied to Prostetrol and Starkoprex commercial tablets with no interference with common tablet additives.

Utilization of a micellar matrix for simultaneous spectrofluorimetric estimation of alfuzosin hydrochloride and vardenafil hydrochloride

A sensitive and direct spectrofluorimetric method was developed for simultaneous quantitation of two co-administered drugs, namely, alfuzosin hydrochloride (AFH) and vardenafil hydrochloride (VRH). Both drugs exhibited native fluorescence properties that could be exploited to assay them in biological fluids with high sensitivity. Spectrofluorimetric analysis of AFH and VRH is based on excitation of both drugs at 265 nm where emission spectra were recorded separately for AFH and VRH at 380 and 485 nm, respectively. Micellar trends in analytical chemistry were adopted to minimize both environmental and occupational hazards, using distilled water and sodium dodecyl sulphate (serves as a micellar medium that enhanced the sensitivity of AFH and VRH) for analysis of both drugs in their raw materials, tablets, and human biological fluids (plasma and urine). Linearity ranges were 1.0-16.0 and 10.0-700.0 ng mL^-1 for AFH and VRH, respectively. The proposed method was successfully assessed for analysis of AFH and VRH in spiked human plasma and urine samples over the following concentrations: 1.0-12.0 ng mL^-1 and 4.0-400.0 ng mL^-1 for both drugs, simultaneously with mean recoveries of 101.08 % and 102.06 % in plasma and 96.75 % and 92.8 % in urine. Statistical analysis of the practical results has proved quite good agreement and revealed there were no significant differences in the accuracy and precision with those obtained by the comparison methods. The proposed method was applied successfully to Prostetrol® and Powerecta® commercial tablets without interference with tablet additives.

Alfuzosin for the medical treatment of benign prostatic hyperplasia and lower urinary tract symptoms: a systematic review of the literature and narrative synthesis

Background:

Lower urinary tract symptoms (LUTS) secondary to benign prostatic hyperplasia (BPH) are a bothersome frequent symptom in adult males. This systematic review analyzed the available evidence on the pharmacokinetic and pharmacodynamic features of alfuzosin, and its clinical efficacy both as monotherapy and in combination with other drugs for the treatment of male LUTS/BPH.

Methods:

A systematic review of the last 10 years was performed using the MEDLINE, EMBASE and Cochrane libraries in March 2020. The protocol for this systematic review was registered on PROSPERO (Central Registration Depository: CRD42020136120) and is available in full on the University of York website.

Results:

Alfuzosin is a quinazoline derivative and, although a nonspecific α1-blocker, exhibits a selective concentration in the prostate compared with plasma in patients with BPH. Three registration trials assessed the safety and efficacy of alfuzosin. The 10 mg daily formulation has a three-layered matrix containing the active substance between two inactive coats allowing a drug release over 20 h. Alfuzosin showed high tolerability, few vasodilatory effects and a low rate of ejaculation disorders over older alpha-blocking compounds thanks to the high uroselectivity of alfuzosin and its preferential concentration at urinary level. Six randomized clinical trials (RCTs) assessed efficacy and safety of alfuzosin versus other alpha-blockers ± placebo: three studies comparing with tamsulosin, one with doxazosin, and two with silodosin or tamsulosin. One RCT investigated the clinical outcomes of alfuzosin with finasteride, two with propiverine and two with phosphodiesterase-5 inhibitors.

Conclusions:

Alfuzosin is an effective drug for the treatment of LUTS/BPH, with a lower rate of sexual disorders compared with other alpha-blockers. Alfuzosin is also safe with low adverse events in case of concomitant antihypertensive therapy and in patients with cardiovascular morbidity. Safety and efficacy of alfuzosin has been reported also in case of combination therapy with antimuscarinic agents and PDE5i.

Alfuzosin and Its Effect on Ejaculatory Dysfunction: A Systematic Review

Studies have demonstrated that alfuzosin not only improves lower urinary tract symptoms (LUTS) but also appears to preserve ejaculatory dysfunction (EjD). The objective of this study was to evaluate the impact of alfuzosin on ejaculatory function using the ‘Male Sexual Health Questionnaire (MSHQ)-EjD Short Form’ – a validated, abridged-version of the 25-item MSHQ specifically assessing EjD. A systematic search of MEDLINE, PubMed, Scopus, Embase, and grey literature was performed in January 2017 to identify relevant cohort studies. Search terms were ‘alfuzosin’, ‘benign prostatic hyperplasia’, ‘ejaculatory dysfunction’ and their synonyms without exclusions. Six cohort studies conducted between 2008 to 2015 were selected for analysis. Three of these were conducted in Korea, one in Thailand, one in China, and one in Tunisia. Overall, 1,371 patients were enrolled in these studies with a median age of 62.3 years. All studies quantified patient LUTS and ejaculatory function using the International Prostate Symptom Score (IPSS) and MSHQ-EjD Short Form, respectively. IPSS had a median decrease of 6.6 while MSHQ-EjD had a median increase of 1.9. This review highlights the very real association between sexual function and LUTS. This systematic review confirms that alfuzosin may improve ejaculatory function in addition to LUTS and should be considered in men who are sexually active or who already complain of deteriorating ejaculation.

Do Preoperative Alpha Blockers Facilitate Ureteroscope Insertion at the Vesico-Ureteric Junction? An Answer from a Prospective Case-Controlled Study

Objective: To evaluate whether alpha blockers facilitate the navigation of the ureteroscope through the ureteric orifice, if administered preoperatively, based on the role of alpha blockers, mainly tamsulosin, in medical expulsive therapy of ureteric calculus. Methods: A prospective, case-control study of 174 patients who underwent ureteroscopic stone removal for lower or mid ureteral calculi between November 2014 and March 2016 was carried out. We included patients >14 years of age who were planned for ureteroscopic stone removal. We divided the patients into two groups, including those who were not prescribed alpha blockers prior to surgery (Group A: no alpha blocker) and those patients who were started on alpha blockers, tamsulosin 0.4 mg, 3 days prior to surgery (Group B: alpha blocker). We excluded patients with stone size >1 cm, spontaneous stone passage prior to surgery, unable to perform ureteroscopy (URS), and previous history of ureteroscopic intervention. Results: Our study included 124 patients, among whom 60 patients were prescribed alpha blockers preoperatively (Group B). The mean age of the study population was 37.62+9.74 (15–64 years) and the mean stone burden was 38.92+8.21 (15.94–58.12 mm2). The difference in rate of ureteroscope negotiation through the ureteric orifice between Groups A and B was not statistically significant (p=0.57). Conclusions: In URS, preoperative administration of alpha blockers failed to improve technical ease and lower complication rate. Further large group, multi-centre studies are required todiscover a definitive role of alpha blockers prior to URS.

Alpha-blockers for the Treatment of Benign Prostatic Hyperplasia

Over the last 2 decades the evolution of alpha-blockers for lower urinary tract symptoms (LUTS)/benign prostatic hyperplasia (BPH) has been to preserve effectiveness, improve tolerability, and eliminate dose titration. Today, alpha-blockers represent the first-line treatment of most men with BPH whereby the primary objective is relief from bothersome LUTS.

Pathophysiology, Clinical Importance, and Management of Neurogenic Lower Urinary Tract Dysfunction Caused by Suprasacral Spinal Cord Injury

Management of persistent lower urinary tract dysfunction resulting from severe thoracolumbar spinal cord injury can be challenging. Severe suprasacral spinal cord injury releases the spinal cord segmental micturition reflex from supraspinal modulation and increases nerve growth factor concentration in the bladder wall, lumbosacral spinal cord, and dorsal root ganglion, which subsequently activates hypermechanosensitive C-fiber bladder wall afferents. Hyperexcitability of bladder afferents and detrusor overactivity can cause urine leaking during the storage phase. During urine voiding, the loss of supraspinal control that normally coordinates detrusor contraction with sphincter relaxation can lead to spinal cord segmental reflex-mediated simultaneous detrusor and sphincter contractions or detrusor-sphincter dyssynergia, resulting in inefficient urine voiding and high residual volume. These disease-associated changes can impact on the quality of life and life expectancy of spinal-injured animals. Here, we discuss the pathophysiology and management considerations of lower urinary tract dysfunction as the result of severe, acute, suprasacral spinal cord injury. In addition, drawing from experimental, preclinical, and clinical medicine, we introduce some treatment options for neurogenic lower urinary tract dysfunction that are designed to: (1) prevent urine leakage arising because of detrusor overactivity during bladder filling, (2) preserve upper urinary tract integrity and function by reducing intravesical pressure and subsequent vesicoureteral reflux, and (3) prevent urinary tract and systemic complications by treating and preventing urinary tract infections.

Use of drug therapy in the management of symptomatic ureteric stones in hospitalised adults: a multicentre, placebo-controlled, randomised controlled trial and cost-effectiveness analysis of a calcium channel blocker (nifedipine) and an alpha-blocker (tamsulosin) (the SUSPEND trial)

BACKGROUND

Ureteric colic, the term used to describe the pain felt when a stone passes down the ureter from the kidney to the bladder, is a frequent reason for people to seek emergency health care. Treatment with the muscle-relaxant drugs tamsulosin hydrochloride (Petyme, TEVA UK Ltd) and nifedipine (Coracten(®), UCB Pharma Ltd) as medical expulsive therapy (MET) is increasingly being used to improve the likelihood of spontaneous stone passage and lessen the need for interventional procedures. However, there remains considerable uncertainty around the effectiveness of these drugs for routine use.

OBJECTIVES

To determine whether or not treatment with either tamsulosin 400 µg or nifedipine 30 mg for up to 4 weeks increases the rate of spontaneous stone passage for people with ureteric colic compared with placebo, and whether or not it is cost-effective for the UK NHS.

DESIGN

A pragmatic, randomised controlled trial comparing two active drugs, tamsulosin and nifedipine, against placebo. Participants, clinicians and trial staff were blinded to treatment allocation. A cost-utility analysis was performed using data gathered during trial participation.

SETTING

Urology departments in 24 UK NHS hospitals.

PARTICIPANTS

Adults aged between 18 and 65 years admitted as an emergency with a single ureteric stone measuring ≤ 10 mm, localised by computerised tomography, who were able to take trial medications and complete trial procedures.

INTERVENTIONS

Eligible participants were randomised 1 : 1 : 1 to take tamsulosin 400 µg, nifedipine 30 mg or placebo once daily for up to 4 weeks to make the following comparisons: tamsulosin or nifedipine (MET) versus placebo and tamsulosin versus nifedipine.

MAIN OUTCOME MEASURES

The primary effectiveness outcome was the proportion of participants who spontaneously passed their stone. This was defined as the lack of need for active intervention for ureteric stones at up to 4 weeks after randomisation. This was determined from 4- and 12-week case-report forms completed by research staff, and from the 4-week participant self-reported questionnaire. The primary economic outcome was the incremental cost per quality-adjusted life-year (QALY) gained over 12 weeks. We estimated costs from NHS sources and calculated QALYs from participant completion of the European Quality of Life-5 Dimensions health status questionnaire 3-level response (EQ-5D-3L™) at baseline, 4 weeks and 12 weeks.

RESULTS

Primary outcome analysis included 97% of the 1167 participants randomised (378/391 tamsulosin, 379/387 nifedipine and 379/399 placebo participants). The proportion of participants who spontaneously passed their stone did not differ between MET and placebo [odds ratio (OR) 1.04, 95% confidence interval (CI) 0.77 to 1.43; absolute difference 0.8%, 95% CI -4.1% to 5.7%] or between tamsulosin and nifedipine [OR 1.06, 95% CI 0.74 to 1.53; absolute difference 1%, 95% CI -4.6% to 6.6%]. There was no evidence of a difference in QALYs gained or in cost between the trial groups, which means that the use of MET would be very unlikely to be considered cost-effective. These findings were unchanged by extensive sensitivity analyses around predictors of stone passage, including sex, stone size and stone location.

CONCLUSIONS

Tamsulosin and nifedipine did not increase the likelihood of stone passage over 4 weeks for people with ureteric colic, and use of these drugs is very unlikely to be cost-effective for the NHS. Further work is required to investigate the phenomenon of large, high-quality trials showing smaller effect size than meta-analysis of several small, lower-quality studies.

TRIAL REGISTRATION

Current Controlled Trials ISRCTN69423238. European Clinical Trials Database (EudraCT) number 2010-019469-26.

FUNDING

This project was funded by the National Institute for Health Research Health Technology Assessment programme and will be published in full in Health Technology Assessment; Vol. 19, No. 63. See the NIHR Journals Library website for further project information.

Controversies in the management of feline urethral obstruction

OBJECTIVE

To discuss areas of differing opinion in the management of feline urethral obstruction and present current evidence to either support or refute common practices.

ETIOLOGY

Urethral obstruction may occur as a result from a functional obstruction (idiopathic obstruction) or a physical obstruction, such as mucous plugs or calculi within the urethra. Potential risk factors for obstruction in cats include predominantly indoor status, decreased water intake, and increased body weight.

DIAGNOSIS

The diagnosis is most commonly made based on history and initial physical exam-straining to urinate, vocalizing, signs of systemic illness, moderate to large firm bladder on abdominal palpation.

THERAPY

Treatment is based on available evidence. The type of IV isotonic crystalloid used does not seem to matter and rate should be determined by need for fluid resuscitation, and replacement of deficit and ongoing losses. Though controversial, cystocentesis appears to be safe and may offer some benefits in initial management. There is evidence to suggest a smaller urethral catheter (3.5 Fr) may be associated with decreased risk of reobstruction. Routine use of antimicrobial agents in hospital is not recommended; they should be dispensed based on culture performed at the time of catheter removal. Though commonly used, evidence in support of antispasmodics is limited and further prospective investigation is needed.

PROGNOSIS

Feline urethral obstruction is associated with 90-95% survival, with reported recurrence rates of 15-40%. Potential factors affecting recurrence include size or duration of indwelling urinary catheter, use of antispasmodic agents, patient age, and indoor-outdoor lifestyle; however, different studies offer conflicting results. Increased water intake and environmental modification do seem to decrease risk of recurrence.

Use of drug therapy in the management of symptomatic ureteric stones in hospitalized adults (SUSPEND), a multicentre, placebo-controlled, randomized trial of a calcium-channel blocker (nifedipine) and an α-blocker (tamsulosin): study protocol for a randomized controlled trial

Background

Urinary stone disease is common, with an estimated prevalence among the general population of 2% to 3%. Ureteric stones can cause severe pain and have a significant impact on quality of life, accounting for over 15,000 hospital admissions in England annually. Uncomplicated cases of smaller stones in the lower ureter are traditionally treated expectantly. Those who fail standard care or develop complications undergo active treatment, such as extracorporeal shock wave lithotripsy or ureteroscopy with stone retrieval. Such interventions are expensive, require urological expertise and carry a risk of complications.

Growing understanding of ureteric function and pathophysiology has led to the hypothesis that drugs causing relaxation of ureteric smooth muscle, such as the selective α-blocker tamsulosin and the calcium-channel blocker nifedipine, can enhance the spontaneous passage of ureteric stones. The use of drugs in augmenting stone passage, reducing the morbidity and costs associated with ureteric stone disease, is promising. However, the majority of clinical trials conducted to date have been small, poor to moderate quality and lacking in comprehensive economic evaluation.

This trial aims to determine the clinical and cost-effectiveness of tamsulosin and nifedipine in the management of symptomatic urinary stones.

Methods/design

The SUSPEND (Spontaneous Urinary Stone Passage ENabled by Drugs) trial is a multicentre, double-blind, randomized controlled trial evaluating two medical expulsive therapy strategies (nifedipine or tamsulosin) versus placebo.

Patients aged 18 to 65 with a ureteric stone confirmed by non-contrast computed tomography of the kidney, ureter and bladder will be randomized to receive nifedipine, tamsulosin or placebo (400 participants per arm) for a maximum of 28 days. The primary clinical outcome is spontaneous passage of ureteric stones at 4 weeks (defined as no further intervention required to facilitate stone passage). The primary economic outcome is a reduction in the incremental cost per quality-adjusted life years, determined at 12 weeks. The analysis will be based on all participants as randomized (intention to treat). The trial has 90% power with a type I error rate of 5% to detect a 10% increase in primary outcome between the tamsulosin and nifedipine treatment groups.

Trial registration

ISRCTN69423238; EudraCT number: 2010-019469-26

In Vitro-In Vivo Correlation Evaluation of Generic Alfuzosin Modified Release Tablets

Alfuzosin, a selective alpha-1a antagonistis is the most recently approved AARAS, with limited cardiac toxicity and exclusively used for lower urinary tract syndromes (LUTS). In order to reduce pill burden and better patient compliance modified release (MR) formulations have been developed. Alfuzosin MR tablet was developed by the use of hot-melt granulation techniques using mono- and diglycerides as rate controlling membranes to minimize health care cost and uses of costly excipients. The other purpose of the study was to evaluate in vitro-in vivo performance of the scale up batch in healthy human subjects for commercialization. The blend uniformity (mean ± RSD%), assay, cumulative percent dissolution at 24 h, hardness, and friability of the biobatch were 100.2 ± 0.05%, 100.43 ± 0.023%, 93.98%, 4.5 kg, 5 min, and 0.08%, respectively. The in vivo pharmacokinetic parameters under fasting conditions between test and reference formulations (Uroxatral 10 mg extended release tablets) were comparable. The 90% CI, geometric mean ratio (%) and power of C_max, AUCT, and AUCI of the fasting study for the test and reference formulation were 99.03% to 122.78%, 109%, 0.998; 92.94% to 116.71%, 104%, 1; 98.17% to 124.01%, 110% 1, respectively. The scale up biobatch showed negligible difference in in vitro properties with respect to the pilot batch. The formulation developed with these agents was safe to use as there were no serious adverse events developed during the conduction of the clinical trial on the healthy subjects. Furthermore, the developed formulation was bioequivalent with respect to rate and extends of absorption to the reference formulation.

Tamsulosin potently and selectively antagonizes human recombinant α(1A/1D)-adrenoceptors: slow dissociation from the α(1A)-adrenoceptor may account for selectivity for α(1A)-adrenoceptor over α(1B)-adrenoceptor subtype

We determined the binding affinity of tamsulosin, a selective α(1)-adrenoceptor antagonist, for human α(1)-adrenoceptor subtypes in comparison with those of other α(1)-adrenoceptor antagonists including silodosin, prazosin, 5-methylurapidil, terazosin, alfuzosin, nafopidil, urapidil and BMY7378. The association and dissociation kinetics of [(3)H]tamsulosin for recombinant human α(1)-adrenoceptor subtypes were compared with those of [(3)H]prazosin. Tamsulosin competitively inhibited [(3)H]prazosin binding to human α(1A)-, α(1B)- and α(1D)-adrenoceptors (pK(i) values were 10.38, 9.33, 9.85) indicating 11 and 3.4-fold higher affinities for human α(1A)-adrenoceptor than those for α(1B)- and α(1D)-adrenoceptors, respectively. The affinity of tamsulosin for the human α(1A)-adrenoceptor was, respectively, 5, 9.9, 38, 120, 280, 400, 1200 and 10000 fold higher than those of silodosin, prazosin, 5-methylurapidil, terazosin, alfuzosin, naftopidil, urapidil and BMY7378, respectively. [(3)H]Tamsulosin dissociated from the α(1A)-adrenoceptor slower than from the α(1B)- and α(1D)-adrenoceptors (α(1B)>α(1D)>α(1A)). Moreover, [(3)H]tamsulosin dissociated slower than [(3)H]prazosin from the α(1A)-adrenoceptor and faster from the α(1B)- and α(1D)-adrenoceptors. In conclusion, tamsulosin potently and selectively antagonized α(1A/1D)-adrenoceptor ligand binding, and slowly dissociated from the α(1A)-adrenoceptor subtype.

Impact of alfuzosin on sexual function in Taiwanese men with benign prostatic hyperplasia

To assess the effect of alfuzosin (XATRAL) 10 mg once daily on sexual function in men with moderate to severe lower urinary tract symptoms (LUTS) associated with benign prostatic hyperplasia (BPH), patients with suggestive symptomatic BPH, an International Prostate Symptom Score (IPSS) >8 (range of scores, 0-35), and sexual attempts at least once per month were enrolled. All patients received alfuzosin 10 mg once daily for 24 weeks and were asked to complete the IPSS test and Male Sexual Health Questionnaire at weeks 0 (baseline), 1, 4, 12, and 24. Other assessments included the International Index of Erectile Function-five-item version (range of scores: 5-25), as well as onset of action and peak urinary flow rate (Q(max)). From September 2006 to May 2008, 279 patients were enrolled from nine centers in Taiwan. At 24 weeks, alfuzosin effectively improved LUTS and quality of life, as demonstrated by a reduction in the IPSS total score (17.3 vs. 9.9, p < 0.001) and the IPSS bother score (3.8 vs. 2.5, p < 0.001). The majority (85%) of patients perceived an improvement of urinary symptoms within 1 month of administration. In patients with an International Index of Erectile Function-five-item version score of ≤16, alfuzosin significantly improved erectile disorder and satisfaction subscores at each time point (p ≤ 0.02). Prolonged-release alfuzosin effectively improved LUTS, quality of life, erectile function, and sexual satisfaction in men with BPH and mild to severe erectile dysfunction. Alfuzosin is an effective treatment option for the management of patients with BPH/LUTS and concomitant sexual dysfunction.

Phenotype pharmacology of lower urinary tract α(1)-adrenoceptors

α(1)-Adrenoceptors are involved in numerous physiological functions, including micturition. However, the pharmacological profile of the α(1)-adrenoceptor subtypes remains controversial. Here, we review the literature regarding α(1)-adrenoceptors in the lower urinary tract from the standpoint of α(1L) phenotype pharmacology. Among three α(1)-adrenoceptor subtypes (α(1A), α(1B) and α(1D)), α(1a)-adrenoceptor mRNA is the most abundantly transcribed in the prostate, urethra and bladder neck of many species, including humans. In prostate homogenates or membrane preparations, α(1A)-adrenoceptors with high affinity for prazosin have been detected as radioligand binding sites. Functional α(1)-adrenoceptors in the prostate, urethra and bladder neck have low affinity for prazosin, suggesting the presence of an atypical α(1)-adrenoceptor phenotype (designated as α(1L)). The α(1L)-adrenoceptor occurs as a distinct binding entity from the α(1A)-adrenoceptor in intact segments of variety of tissues including prostate. Both the α(1L)- and α(1A)-adrenoceptors are specifically absent from Adra1A (α(1a)) gene-knockout mice. Transfection of α(1a)-adrenoceptor cDNA predominantly expresses α(1A)-phenotype in several cultured cell lines. However, in CHO cells, such transfection expresses α(1L)- and α(1A)-phenotypes. Under intact cell conditions, the α(1L)-phenotype is predominant when co-expressed with the receptor interacting protein, CRELD1α. In summary, recent pharmacological studies reveal that two distinct α(1)-adrenoceptor phenotypes (α(1A) and α(1L)) originate from a single Adra1A (α(1a)-adrenoceptor) gene, but adrenergic contractions in the lower urinary tract are predominantly mediated via the α(1L)-adrenoceptor. From the standpoint of phenotype pharmacology, it is likely that phenotype-based subtypes such as the α(1L)-adrenoceptor will become new targets for drug development and pharmacotherapy.

α(1)-Adrenoceptors in the urinary tract

α(1)-Adrenoceptors have been identified and characterized extensively by functional, radioligand-binding, and molecular biological techniques. Molecular clones have been isolated for three α(1)-subtypes (α(1a), α(1b), and α(1d)), and these subtypes are also functionally characterized. α(1)-Adrenoceptors are present in the prostate, urethra, bladder (urothelium, smooth muscle, and afferent nerves), ureter, vas deferens, peripheral ganglia, nerve terminals, vascular tissues, and central nervous system (CNS), and they could all potentially influence overall urinary function and contribute to both the therapeutic and adverse effects of α(1)-adrenoceptor antagonists in patients with benign prostatic hyperplasia (BPH) and lower urinary tract symptoms (LUTS). This review aimed to discuss the relevant physiological and pharmacological roles and molecular biology of α(1)-adrenoceptor subtypes in the prostate, urethra, bladder, ureter, and CNS.

Medical treatment of benign prostatic hyperplasia

Pharmaceutical preparations are commonly used for benign prostate hyperplasia. This article reviews the current understanding of the natural history of the condition and the literature regarding medical treatment.

Alpha1-, alpha2- and beta-adrenoceptors in the urinary bladder, urethra and prostate

1 We have systematically reviewed the presence, functional responses and regulation of alpha(1)-, alpha(2)- and beta-adrenoceptors in the bladder, urethra and prostate, with special emphasis on human tissues and receptor subtypes. 2 Alpha(1)-adrenoceptors are only poorly expressed and play a limited functional role in the detrusor. Alpha(1)-adrenoceptors, particularly their alpha(1A)-subtype, show a more pronounced expression and promote contraction of the bladder neck, urethra and prostate to enhance bladder outlet resistance, particularly in elderly men with enlarged prostates. Alpha(1)-adrenoceptor agonists are important in the treatment of symptoms of benign prostatic hyperplasia, but their beneficial effects may involve receptors within and outside the prostate. 3 Alpha(2)-adrenoceptors, mainly their alpha(2A)-subtype, are expressed in bladder, urethra and prostate. They mediate pre-junctional inhibition of neurotransmitter release and also a weak contractile effect in the urethra of some species, but not humans. Their overall post-junctional function in the lower urinary tract remains largely unclear. 4 Beta-adrenoceptors mediate relaxation of smooth muscle in the bladder, urethra and prostate. The available tools have limited the unequivocal identification of receptor subtypes at the protein and functional levels, but it appears that the beta(3)- and beta(2)-subtypes are important in the human bladder and urethra, respectively. Beta(3)-adrenoceptor agonists are promising drug candidates for the treatment of the overactive bladder. 5 We propose that the overall function of adrenoceptors in the lower urinary tract is to promote urinary continence. Further elucidation of the functional roles of their subtypes will help a better understanding of voiding dysfunction and its treatment.

Alpha1A/L-adrenoceptors mediate contraction of the circular smooth muscle of the pig urethra

Sympathetically mediated urethral tone is essential for the maintenance of continence and involves the activation of postjunctional alpha(1)-adrenoceptors. This study characterizes the alpha(1)-adrenoceptor subtypes responsible for mediating contraction of the urethral circular smooth muscle of the pig. The potency order of a number of agonists and the affinities of several receptor selective antagonists were determined on pig-isolated circular smooth muscle strips in the presence of cocaine (1 microm) and corticosterone (10 microm) to inhibit amine uptake and propranolol (1 microm) to antagonize beta-adrenoceptors. The potency order for agonists was N-[5-(4,5-dihydro-1H-imidazol-2yl)-2-hydroxy-5,6,7,8-tetrahydronaphthalen-1-yl]methanesulphonamide (A61603) > noradrenaline = phenylephrine = M6434 > methoxamine with pEC(50) values of 7.3, 5.8, 5.7, 5.6 and 5.0 respectively. 4 The alpha(1D)-adrenoceptor-selective antagonist 8-[2-[4-(2-methoxyphenyl)-1-piperazinyl]ethyl]-8-azaspiro[4,5]decane-7,9-dione (BMY7378) caused rightward shifts of the concentration-response curves to noradrenaline, yielding a low affinity estimate (6.6) for the urethral receptor. The alpha(1A)-adrenoceptor-selective antagonists, RS100329 and 5-methylurapidil, gave relatively high affinity estimates (9.6 and 8.8 respectively) for this receptor. All three antagonists produced Schild plots with slopes close to unity but did reduce maximum responses at higher concentrations. Prazosin antagonized responses of the urethra to noradrenaline, yielding a mean affinity estimate of 9.0. Although the Schild plot for prazosin again had a slope of unity, this drug also reduced maximum responses to noradrenaline at all concentrations examined (10-100 nm). N-[2-(2-cyclopropylmethoxyphenoxy)ethyl]-5-chloro-alpha,alpha-dimethyl-1H-indole-3-ethanamide (RS17053), which discriminates between responses mediated via alpha(1A) (high affinity) and alpha(1L)-adrenoceptors (low affinity) at concentrations up to 3 microm, failed to antagonize responses of the urethra. 5 These results suggest that contraction of urethral circular smooth muscle in the pig is mediated via a single population of adrenoceptors with the pharmacological characteristics of the alpha(1A/L)-adrenoceptor, most probably the alpha(1L)-adrenoceptor.

Differentiated rabbit prostatic stromal cells in primary culture display functional α1A-adrenoceptors

AIMS

BPH is characterized by uncontrolled proliferation and increased contractility of prostatic smooth muscle cells. The activation of alpha1-adrenoceptors (alpha1-AR) seems involved in the latter event, but the lack of in vitro models expressing these receptors has hampered a more specific characterization of their role. In order to do so, we attempted to develop a new model of rabbit cultured prostatic stromal cells (PSC) in a non-proliferative and differentiated state.

METHODS

The expression of cytoskeletal and stromal markers was confirmed by immunohistochemistry on primary cultured PSC. Alpha1-AR subtype expression was assessed by RT-PCR, while receptor coupling to the ERK1/ERK2 and calcium pathways was studied by Western Blot and Fura-2 calcium imaging, respectively.

RESULTS

Cells grown under non-proliferative conditions displayed a differentiated phenotype, with expression of contractile cytoskeletal and stromal proteins. Furthermore, the alpha1A-AR was shown to activate ERK1/ERK2 as well as calcium signaling.

CONCLUSION

These results emphasize the interest of this model for the characterization of PSC adrenergic regulation, in particular through the little-known alpha1A-AR.

Role of the newer alpha, -adrenergic-receptor antagonistsin the treatment of benign prostatic hyperplasia-related lower urinary tract symptoms

BACKGROUND

Although initially introduced for the management of hypertension, alpha(1)-adrenergic-receptor antagonists (alpha1-blockers) have become the standard of care for the medical management of benign prostatic hyperplasia (BPH)-related lower urinary tract symptoms (LUTS). However, these agents have the potential to produce orthostatic hypotension and other blood pressure-related adverse effects in normotensive patients and in those receiving concurrent treatment with other antihypertensive agents. As a result, more "uroselective," less vasoactive alpha(1)-blockers have been developed.

OBJECTIVE

This article reviews current information on the role of alpha(1)-blockers in the treatment of BPH-related LUTS. The focus is on tamsulosin and alfuzosin, newer "uroselective" agents in this class that have a decreased potential for cardiovascular adverse effects.

METHODS

Relevant articles were identified through a search of the English-language literature indexed on MEDLINE and the proceedings of scientific meetings from 1976 to 2003. The search terms were benign prostatic hyperplasia treatment, alpha(1)-adrenergic-receptor blocker, uroselectivity, lower urinary tract symptoms, complications, and cardiovascular.

RESULTS

Tamsulosin has selectivity for the a alpha(1) and alpha(1d) receptor subtypes. Alfuzosin, although not receptor subtype selective, is clinically "uroselective" and does not significantly affect vascular alpha-adrenergic receptors. Both agents are efficacious in relieving LUTS and have a decreased potential for such cardiovascular adverse effects as postural hypotension. Common adverse events with these agents include dizziness and asthenia.

CONCLUSION

Based on the available data, "uroselective" alpha(1)-blockers should be considered over older, more vasoactive agents for the medical management of LUTS, particularly in patients with BPH and hypertension.

Evaluation of tamsulosin and alfuzosin activity in the rat vas deferens: relevance to ejaculation delays

The effect of two alpha-adrenergic receptor antagonists widely employed in the therapy of benign prostatic hyperplasia, tamsulosin [(-)-(R)-5-[2-[[2-(0-ethoxyphenoxy) ethyl]amino]propyl]-2-methoxybenzenesulfonamide] and alfuzosin [(+/-)-N-[3-[(4-amino-6,7-dimethoxy-2-quinazolinyl) methylamino]propyl] tetrahydro-2-furancarboxamide], was investigated in the rat vas deferens. Because several clinical studies have shown that tamsulosin causes ejaculatory disorders, this study also evaluated the possible mechanisms implicated in these disorders by comparing the effect of tamsulosin with that of alfuzosin. Tamsulosin competitively antagonized the contractions induced by noradrenaline in vitro in the epididymal portion of the vas deferens with a potency pA(2) value of 9.2 +/- 0.8. In the prostatic portion, tamsulosin increased the amplitude of intermittent spikes induced by exogenous noradrenaline (100-1000 microM). In both portions of the vas deferens, alfuzosin behaved as an alpha-adrenergic antagonist blocking the contractions induced by exogenous noradrenaline without altering spikes. The administration of tamsulosin (3 microg/kg i.v.) significantly reduced the contractions evoked by electrical pulses in the epididymal portion, whereas it increased those produced in the prostatic portion. Intravenous tamsulosin antagonized the contraction produced by exogenous noradrenaline, whereas alfuzosin administration (10 microg/kg i.v.) did not change the electrically induced contractions in both portions of the rat vas deferens and did not antagonize the contractions produced by exogenous noradrenaline. The fact that tamsulosin unusually enhances noradrenaline-induced intermittent spike contractions and nerve stimulation-induced twitches in the prostatic portions might be linked to its greater propensity to cause sexual dysfunctions.

Effects of tamsulosin on hypogastric nerve stimulation-induced intraurethral pressure elevation in male and female dogs under anesthesia

The aim of the present study was to investigate the effects of tamsulosin, an alpha(1)-adrenoceptor antagonist, on hypogastric nerve stimulation-induced intraurethral pressure elevation in anesthetized male and female dogs and to evaluate sex differences in these effects. Additionally, the effects of tamsulosin were also compared with those of other alpha(1)-adrenoceptor antagonists, namely prazosin, naftopidil and urapidil. Tamsulosin dose-dependently inhibited hypogastric nerve stimulation-induced intraurethral pressure elevation, with doses required to induce 50% inhibition of the elevation (ED(50) values) of 0.72 and 0.74 microg/kg i.v. in anesthetized male and female dogs, respectively. Mean arterial blood pressure slightly decreased after administration of tamsulosin at a dose which inhibited intraurethral pressure elevation almost completely. Prazosin, naftopidil and urapidil also inhibited increases in intraurethral pressure in a dose-dependent fashion, but caused decreases in mean arterial blood pressure at the same doses. The estimated rank order of inhibitory potency for urethral response was tamsulosin>prazosin>naftopidil=urapidil. In conclusion, tamsulosin dose-dependently inhibited increases in intraurethral pressure with little effect on mean arterial blood pressure in both male and female dogs, and these effects were almost equipotent. These results indicate that tamsulosin will be useful in the treatment of dysuria associated with lower urinary tract symptoms in women as well as men.

Alfuzosin: a review of the therapeutic use of the prolonged-release formulation given once daily in the management of benign prostatic hyperplasia

Alfuzosin, a quinazoline derivative, is a selective and competitive alpha(1)-adrenoceptor antagonist. It distributes preferentially in the prostate, compared with plasma, and decreases the sympathetically controlled tone of prostatic smooth muscle. As a result lower urinary tract symptoms suggestive of benign prostatic hyperplasia (BPH) are improved. The once-daily formulation of alfuzosin contains inactive barrier layers which have been added to the planar surfaces of compressed tablets. Drug release is sustained over 20 hours with a near constant dissolution rate between 2 and 12 hours. Mean values for area under the plasma concentration-time curve over 24 hours (AUC(24)) were similar after administration of prolonged-release alfuzosin 10mg once daily and immediate-release alfuzosin 2.5mg three times daily. Likewise, similar AUC(24) values were reported when prolonged-release alfuzosin 10mg once daily and sustained-release alfuzosin 5mg twice daily were compared. These data suggest that these alfuzosin regimens provide similar average systemic exposure. Data from short- (3 months) and long-term (up to 12 months) clinical trials show that the prolonged-release formulation of alfuzosin controls the symptoms associated with BPH as effectively as immediate-release alfuzosin 2.5mg three times daily and clinical improvement is maintained for up to 1 year. Improvements in International Prostate Symptom Score, maximum urinary flow rate and quality-of-life index were improved to a similar extent in patients treated with immediate- or prolonged-release alfuzosin and improvements were statistically significant compared with placebo. Prolonged-release alfuzosin 10mg is well tolerated and the overall incidence of adverse events is similar to that seen with placebo. The once-daily formulation of alfuzosin 10mg caused fewer vasodilatory adverse events than immediate-release alfuzosin 2.5mg three times daily and caused only slight decreases in systolic and diastolic blood pressure which were not clinically significant and did not differ significantly from those with placebo. No dosage titration is required. The incidence of ejaculatory disorders was <1%.

CONCLUSION

Prolonged-release alfuzosin 10mg once daily controls symptoms associated with BPH throughout a 24-hour dosage interval as effectively as immediate-release alfuzosin 2.5mg three times daily but with fewer vasodilatory adverse events. A nonblind extension study showed that clinical benefits were maintained for up to 1 year and the once-daily 10mg formulation continued to be well tolerated, particularly in terms of cardiovascular effects and sexual function. Thus, for the medical management of men with BPH, prolonged-release alfuzosin 10mg is an effective, well tolerated and convenient treatment option.

Intakes of energy and macronutrients and the risk of benign prostatic hyperplasia

BACKGROUND

Benign prostatic hyperplasia (BPH) is a common disease of older men. Although the etiology remains unclear, nutritional factors may have an effect on the disease.

OBJECTIVE

Because the literature on the relations between macronutrient intakes and BPH risk is limited, we examined these relations among men in the Health Professionals Follow-up Study.

DESIGN

We followed men aged 40-75 y from baseline in 1986 to 1994. Total BPH cases (n = 3523) comprised men who reported BPH surgery (n = 1589) or who did not undergo surgery but scored 15-35 points on the lower urinary tract symptom questionnaire of the American Urological Association (n = 1934); non-cases were men who scored < or = 7 points (n = 24388). Odds ratios (ORs) and 95% CIs were calculated by using multivariate logistic regression.

RESULTS

The ORs rose with increasing total energy intake in a comparison of the highest and lowest quintiles for total BPH (OR: 1.29; 95% CI: 1.14, 1.45) and symptoms of BPH (1.43; 1.23, 1.66). Energy-adjusted total protein intake was positively associated with total BPH (1.18; 1.05, 1.33) and BPH surgery (1.26; 1.06, 1.49). Energy-adjusted total fat intake was not associated with risk of total BPH, but intakes of eicosapentaenoic, docosahexaenoic, and arachidonic acids were associated with a moderate increase in risk of total BPH.

CONCLUSIONS

We observed modest direct associations between BPH and intakes of total energy, protein, and specific long-chain polyunsaturated fatty acids. Because eicosapentaenoic, docosahexaenoic, and arachidonic acids are highly unsaturated fatty acids, our findings support a possible role of oxidative stress in the etiology of BPH.

Are all alpha-blockers created equal? An update

alpha-Receptor blockers, used to treat lower urinary tract symptoms, exert effects on areas of the body other than the prostate where alpha-receptors are located, including the blood vessels and the central nervous system. alpha-Receptors in the central and peripheral nervous system may be involved in bladder activation. alpha(1a)-Receptors are the appropriate target in men with obstructive symptoms, although alpha(1d)-receptors may also be important in patients with irritative symptoms. There is conflicting evidence about the selectivity of alpha-blockers. Clinical trials of these agents do not necessarily reflect results observed in animal and laboratory studies on uroselectivity. The few published comparator studies of alpha-blockers indicate similar efficacies, although side-effect profiles differ somewhat. Randomized, controlled studies of different alpha-blockers with sufficient power to detect differences in side effects between agents are needed.

Alfuzosin: overview of pharmacokinetics, safety, and efficacy of a clinically uroselective alpha-blocker

Efficacy and safety of alfuzosin administered as 3-times-daily and 2-times-daily formulations have been previously demonstrated in placebo-controlled studies, and these formulations have been commercially available in many countries. A once-daily formulation of alfuzosin administered through a novel prolonged-release system has been recently developed to improve the convenience of dosing and to provide optimal pharmacokinetic coverage over 24 hours. The results of 2 double-blind, placebo-controlled phase 3 studies in patients with lower urinary tract symptoms associated with benign prostatic hyperplasia suggests that 10 mg of alfuzosin administered once daily without dose titration is superior to placebo in terms of symptom and urinary flow rate improvement. Orthostatic hypotension and first-dose phenomenon related to the alpha-blocking property were rare. The incidences of asthenia and fatigue were comparable to those seen with placebo. Ejaculatory disorders were very rare. The most frequently reported adverse event potentially related to alpha blockade was dizziness, which occurred in 5.0% of patients treated with 10 mg alfuzosin compared with 2.1% of patients given placebo.

Efficacy and safety of once-daily alfuzosin in the treatment of lower urinary tract symptoms and clinical benign prostatic hyperplasia: a randomized, placebo-controlled trial

OBJECTIVES

To assess the efficacy and safety, and determine the optimal dosage, of a once-daily (OD) formulation of the clinically uroselective alpha(1)-blocker, alfuzosin, in patients with lower urinary tract symptoms and symptomatic benign prostatic hyperplasia.

METHODS

Five hundred thirty-six patients were randomized to receive alfuzosin (10 mg OD or 15 mg OD), without initial dose titration, or placebo in a 3-month double-blind trial conducted in North America. The primary efficacy criteria were improvement in symptoms (International Prostate Symptom Score) and peak urinary flow rate.

RESULTS

Alfuzosin was significantly more effective than placebo in improving the symptoms and peak urinary flow rate from the first follow-up visit (day 28). The mean change in the International Prostate Symptom Score from baseline at endpoint was -3.6 and -3.4 with alfuzosin 10 mg and 15 mg, respectively, compared with -1.6 with placebo (alfuzosin 10 mg versus placebo, P = 0.001; alfuzosin 15 mg versus placebo, P = 0.004). The median increase in the peak urinary flow rate was +1.1 mL/s and +1.0 mL/s with alfuzosin 10 mg and 15 mg, respectively, compared with 0.0 mL/s with placebo (P = 0.0006 versus placebo for both dose groups). The patients' quality of life also significantly improved with both alfuzosin doses. Overall, alfuzosin at both doses was well tolerated. The incidence of orthostatic hypotension as determined by systematic blood pressure measurements with both doses of alfuzosin was similar to placebo. No clinically relevant ejaculation disorders were observed with alfuzosin.

CONCLUSIONS

Alfuzosin 10 mg OD, administered without dose titration, provides effective relief from the symptoms of benign prostatic hyperplasia with no additional benefit from a 15-mg dose. It is well tolerated from a cardiovascular viewpoint and is not associated with abnormal ejaculation.

Selectivity of oxymetazoline for urethral pressure vs blood pressure in the anaesthetized female rabbit

OBJECTIVE

The aim of this study was to test alpha-adrenergic reference agonists for tissue selectivity in the urethra and to pharmacologically characterize the functional alpha-adrenoceptor type of the female rabbit urethra in vivo.

MATERIAL AND METHODS

The effect of alpha-adrenergic agonists and antagonists on the urethral pressure was compared with that on blood pressure and heart rate measured simultaneously in the anaesthetized female rabbit.

RESULTS

Oxymetazoline, NS-49, phenylephrine and phenylpropanolamine enhanced the urethral pressure in a dose-dependent manner. Phenylephrine and phenylpropanolamine also enhanced the blood pressure with significantly lower ED50 (dose that gives half of the maximal enhancing effect) values than for the urethral pressure. This was in contrast to oxymetazoline and NS-49. The ED50 values for oxymetazoline on urethral pressure, and systolic and diastolic blood pressure were 0.00067, 0.0030 and 0.0020 mg/kg, respectively. The ED50 values for NS-49 on urethral pressure, and systolic and diastolic blood pressure were 0.019, 0.21 and 0.18 mg/kg, respectively. Clonidine and UK 14,304 had no effect on urethral or blood pressure. The oxymetazoline-evoked increase in urethral pressure was inhibited by WB-4101 with an ID50 (dose that gives half of the inhibitory effect) significantly lower than that for rauwolscine.

CONCLUSIONS

The results suggest that in the female rabbit in vivo activation of alpha1-adrenoceptors increased the urethral pressure. Phenylephrine and phenylpropanolamine, in contrast to oxymetazoline and NS-49, selectively enhanced blood pressure as compared with urethral pressure. Provided that the present results also have validity in humans, it would seem possible to develop urethra-selective drugs for treatment of stress incontinence with few or no cardiovascular side-effects.

Subtypes of functional alpha1- and alpha2-adrenoceptors

In this review, subtypes of functional alpha1- and alpha2-adrenoceptors are discussed. These are cell membrane receptors, belonging to the seven transmembrane spanning G-protein-linked family of receptors, which respond to the physiological agonists noradrenaline and adrenaline. Alpha1-adrenoceptors can be divided into alpha1A-, alpha1B- and alpha1D-adrenoceptors, all of which mediate contractile responses involving Gq/11 and inositol phosphate turnover. A 4th alpha1-adrenoceptor, the alpha1L-, has been postulated to mediate contractions in some tissues, but its relationship to cloned receptors remains to be established. Alpha2-adrenoceptors can be divided into alpha2A-, alpha2B- and alpha2C-adrenoceptors, all of which mediate contractile responses. Prejunctional inhibitory alpha2-adrenoceptors are predominantly of the alpha2A-adrenoceptor subtype (the alpha2D-adrenoceptor is a species orthologue), although alpha2C-adrenoceptors may also occur prejunctionally. Although alpha2-adrenoceptors are linked to inhibition of adenylate cyclase, this may not be the primary signal in causing smooth muscle contraction; likewise, prejunctional inhibitory actions probably involve restriction of Ca2+ entry or opening of K+ channels. Receptor knock-out mice are beginning to refine our knowledge of the functions of alpha-adrenoceptor subtypes.

Relationship between the effects of alfuzosin on rat urethral and blood pressures and its tissue concentrations

This study was undertaken in order to establish the alpha1-antagonist effects of alfuzosin on phenylephrine-induced increases in urethral and arterial blood pressures at 1 and 6 hours post dosing (10 mg/kg, p.o.). At each time, plasma and prostatic concentrations of alfuzosin were measured and correlations between tissue concentrations and pharmacological effects were calculated. At one and six hours post dosing, alfuzosin markedly shifted the urethral and arterial dose response curve to phenylephrine. At one hour, prostatic concentration was 4.1 times greater than plasma concentration (363 ng/g vs 88 ng/ml) and at 6 hours this ratio reached 8.6 times (167 ng/g vs 20 ng/ml). By taking together the data points obtained at 1 and 6 hours we showed that the effects of alfuzosin on urethral pressure were correlated with prostate levels (r=0.906, p<0.01) and the effects on arterial blood pressure were correlated with plasma levels (r=0.941, p<0.01). These results suggest that a preferential distribution of alfuzosin in prostatic tissue may play a role in its functional uroselectivity.

Alpha-adrenoceptors and vascular regulation: molecular, pharmacologic and clinical correlates

This manuscript is intended to provide a comprehensive review of the alpha-adrenoceptors (ARs) and their role in vascular regulation. The historical development of the concept of receptors and the division of the alpha-ARs into alpha 1 and alpha 2 subtypes is traced. Emphasis will be placed on current understanding of the specific contribution of discrete alpha 1- and alpha 2-AR subtypes in the regulation of the vasculature, selective agonists and antagonists for these receptors, the second messengers utilized by these receptors, the myoplasmic calcium pathways activated to initiate smooth muscle contraction, as well as the clinical uses of agonists and antagonists that work at these receptors. New information is presented that deals with the molecular aspects of ligand interactions with specific subdomains of these receptors, as well as mRNA distribution and the regulation of alpha 1- and alpha 2-AR gene transcription and translation.

Analysis of alpha1-adrenoceptors in rabbit lower urinary tract and mesenteric artery

In this study, we have investigated the effects of a series of alpha1-adrenoceptor antagonists on the phenylephrine-mediated contractions of rabbit isolated prostate, urethra, trigone and mesenteric artery. With the exception of RS-17053 (N-[2-(2-cyclopropylmethoxyphenoxy)ethyl]-5-chloro-alpha,alpha-dim ethyl-1 H-indole-3-ethanamine hydrochloride), the antagonists displayed the lowest potency in the urethra. Catecholamine uptake1 and uptake2 appeared not to be the cause for the low pK(B)/pA2 values obtained in the urethra because cocaine and corticosterone had no effect on the potency of phenylephrine in this tissue. The low potencies displayed by prazosin. RS-17053 and HV723 (alpha-ethyl-3,4,5-trimethoxy-alpha-(3-((2-(2-methoxyphenoxy)ethyl)amino )propyl)benzene-acetonitrile fumarate) suggest that the functional receptors in all four tissues belong to the alpha(1L)-adrenoceptor class. Whether or not the significant between-tissue differences in antagonist potencies are due to heterogeneity of this receptor class remains to be elucidated.

Prostatic alpha 1-adrenoceptors and uroselectivity

BACKGROUND

alpha 1-adrenoceptor antagonists (blockers) are now commonly used in the treatment of the symptoms of lower urinary tract obstruction. Originally phenoxybenzamine, a non-selective antagonist at both alpha 1- and alpha 2-adrenoceptors, was used by Marco Caine. In an attempt to minimize side effects, selective alpha 1-antagonists, e.g. prazosin, were subsequently developed. More recently, agents such as alfuzosin, doxazosin, terazosin, and tamsulosin have been introduced and claims of "uroselectivity" and "prostate" selectivity have emerged.

METHODS

This review attempts to put these claims into perspective and represents a comprehensive analysis of all pre-clinical and clinical data including several papers from the Japanese literature. An attempt is made to define what is meant by selectivity at various levels including the test tube, in the laboratory animal and, most importantly, in the clinical context of the whole patient.

CONCLUSIONS

The conclusions are interpreted within the context of the subdivision of the alpha 1-adrenoceptor into alpha 1A, alpha 1B, and alpha 1D subtypes.