Drugs for treatment of benign prostatic hyperplasia: affinity comparison at cloned alpha 1-adrenoceptor subtypes and in human prostate

Determination of tamsulosin in plasma of healthy Chinese male subjects by a novel and simple LC-MS/MS method and its application to pharmacokinetic studies

Tamsulosin, the first highly selective α1-adrenoceptor antagonist, is widely used for urination disorders caused by benign prostatic hyperplasia (BPH). The pharmacokinetics and safety of 0.2 mg tamsulosin hydrochloride sustained-release capsules were evaluated in 60 healthy Chinese male subjects under fasting and fed conditions in this study. A simple, sensitive, and robust liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed and validated for the quantification of tamsulosin in human plasma, which has been applied to pharmacokinetic study. The analyte and internal standard (tamsulosin-d5) were extracted by protein precipitation, and separated on a ZORBAX Eclipse XDB-C18 column (4.6 × 50 mm,1.8 µm; Agilent Tech) using a gradient elution with mobile phases methanol and 5 mM ammonium acetate. The linear range was 0.05-15.0 ng/mL. It showed good selectivity in normal, hyperlipidemic, and hemolyzed blank matrices. The CV (%) of intra-batch precision was <4.4% and the RE (%) of accuracy was in the range of -5.0%-6.7%; the CV (%) of inter-batch precision was <-5.8% and the RE (%) of accuracy was in the range of 1.2%-4.0%. The mean extraction recovery for the analyte was 102.1 ± 3.75% and for the IS was 102.2 ± 2.00%. Two formulations were considered bioequivalent under fasting and fed conditions, and the 90% confidence intervals for the geometric mean test/reference ratios were within the predetermined range of 80%-125%. A single oral dose of 0.2 mg tamsulosin hydrochloride sustained-release capsule was well-tolerated throughout the clinical trial, and no > Grade 1 adverse events (AEs) and serious AEs occurred during the trial.

Orthostatic Hypotension in Benign Prostatic Hyperplasia Patients and Its Association With Alpha-1 Antagonist Use: A Comprehensive Literature Review

Orthostatic hypotension (OH) is frequently observed in benign prostatic hyperplasia (BPH) patients undergoing alpha-1 adrenergic antagonist (A1AA) therapy. While previous studies have acknowledged the prevalence of OH in BPH patients on A1AAs, limited data exist on ranking the safety of different A1AAs. This comprehensive review explores the underlying mechanisms of OH, examines numerous factors influencing its development, and provides insights into effective treatment strategies such as hydration, gradual postural changes, leg exercises, compression stockings, and tilt-table training for BPH management. The review highlights the significance of individualized care, interdisciplinary collaboration, and further research to optimize A1AA treatment, improve patient outcomes, and enhance quality of life.

Physiologically based pharmacokinetic (PBPK) modelling of tamsulosin related to CYP2D6*10 allele

Tamsulosin, a selective [Formula: see text]-adrenoceptor blocker, is commonly used for alleviation of lower urinary tract symptoms related to benign prostatic hyperplasia. Tamsulosin is predominantly metabolized by CYP3A4 and CYP2D6 enzymes, and several studies reported the effects of CYP2D6 genetic polymorphism on the pharmacokinetics of tamsulosin. This study aims to develop and validate the physiologically based pharmacokinetic (PBPK) model of tamsulosin in CYP2D6*wt/*wt, CYP2D6*wt/*10, and CYP2D6*10/*10 genotypes, using Simcyp® simulator. Physicochemical, and formulation properties and data for absorption, distribution, metabolism and excretion were collected from previous publications, predicted in the simulator, or optimized in different CYP2D6 genotypes. The tamsulosin PBPK model in CYP2D6*wt/*wt and CYP2D6*wt/*10 genotypes were developed based on the clinical pharmacokinetic study where a single oral dose of 0.2 mg tamsulosin was administered to 25 healthy Korean male volunteers with CYP2D6*wt/*wt and CYP2D6*wt/*10 genotypes. A previous pharmacokinetic study was used to develop the model in CYP2D6*10/*10 genotype. The developed model was validated using other clinical pharmacokinetic studies not used in development. The predicted exposures via the PBPK model in CYP2D6*wt/*10 and CYP2D6*10/*10 genotype was 1.23- and 1.76-fold higher than CYP2D6*wt/*wt genotype, respectively. The simulation profiles were visually similar to the observed profiles, and fold errors of all development and validation datasets were included within the criteria. Therefore, the tamsulosin PBPK model in different CYP2D6 genotypes with regards to CYP2D6*10 alleles was appropriately established. Our model can contribute to the implementation of personalized pharmacotherapy of patients, appropriately predicting the pharmacokinetics of tamsulosin reflecting their demographic and CYP2D6 genotype characteristics without unnecessary drug exposure.

An inhibitory effect of Berberine from herbal Coptis chinensis Franch on rat detrusor contraction in benign prostatic hyperplasia associated with lower urinary tract symptoms

ETHNOPHARMACOLOGICAL RELEVANCE

Coptis chinensis Franch (CCF), also known as Huang Lian in China, is a traditional Chinese medicine that commonly used for more than 2000 years. Clinically, CCF often used as anti-inflammatory, immune regulation and other effects. It has been reported that the decoction containing CCF can be used for the treatment of benign prostatic hyperplasia (BPH) or lower urinary tract symptoms (LUTS).

AIM OF THE STUDY

This research aims to investigate the effect of CCF on inhibition of BPH development in vivo and in vitro, and further identify the active compound (s) and the possible mechanism involved in BPH-related bladder dysfunction.

MATERIALS AND METHODS

Oestrodial/testosterone-induced BPH rat model was established as the in vivo model. The prostate index (PI) was calculated, the pathogenesis was analyzed and the micturition parameters were determined in the shamed-operated, BPH model and BPH + CCF groups after 4-week administration. The tension in detrusor strips was then assessed upon KCl or ACh stimulation with or without incubation of CCF or active compounds. To further investigate the signaling involved, rat detrusor cells were cultured as the in vitro models, the instantaneous calcium influx was measured and the ROCK-1 expression was detected.

RESULTS

Increased PI value and the aggravated prostatic pathology were observed with voiding dysfunction in BPH rats, which were significantly blocked by oral CCF taken. ACh or KCl-induced contractile responses in detrusor strips were significantly inhibited and the micturition parameters were improved when incubation with CCF or its active compounds such as berberine. Both CCF and berberine suppressed the cellular calcium influx and ROCK-1 expression upon ACh stimulation, demonstrating that berberine was one of the active compounds that contributed to CCF-improved micturition symptoms and function.

CONCLUSIONS

Taken together, our findings give evidence that CCF and its active compound berberine inhibited BPH and bladder dysfunction via Ca²⁺ and ROCK signaling, supporting their clinical use for BPH and BPH-related LUTS treatment.

Drug Repositioning of the α1-Adrenergic Receptor Antagonist Naftopidil: A Potential New Anti-Cancer Drug?

Failure of conventional treatments is often observed in cancer management and this requires the development of alternative therapeutic strategies. However, new drug development is known to be a high-failure process because of the possibility of a lower efficacy than expected for the drug or appearance of non-manageable side effects. Another way to find alternative therapeutic drugs consists in identifying new applications for drugs already approved for a particular disease: a concept named "drug repurposing". In this context, several studies demonstrated the potential anti-tumour activity exerted by α1-adrenergic receptor antagonists and notably renewed interest for naftopidil as an anti-cancer drug. Naftopidil is used for benign prostatic hyperplasia management in Japan and a retrospective study brought out a reduced incidence of prostate cancer in patients that had been prescribed this drug. Further studies showed that naftopidil exerted anti-proliferative and cytotoxic effects on prostate cancer as well as several other cancer types in vitro, as well as ex vivo and in vivo. Moreover, naftopidil was demonstrated to modulate the expression of Bcl-2 family pro-apoptotic members which could be used to sensitise cancer cells to targeting therapies and to overcome resistance of cancer cells to apoptosis. For most of these anti-cancer effects, the molecular pathway is either not fully deciphered or shown to involve α1-adrenergic receptor-independent pathway, suggesting off target transduction signals. In order to improve its efficacy, naftopidil analogues were designed and shown to be effective in several studies. Thereby, naftopidil appears to display anti-cancer properties on different cancer types and could be considered as a candidate for drug repurposing although its anti-cancerous activities need to be studied more deeply in prospective randomized clinical trials.

The impact of the bladder wall thickness on the outcome of the medical treatment using alpha-blocker of BPH patients with LUTS

OBJECTIVES

To evaluate whether the outcome of medical treatment with α 1 receptor blocker in Benign prostatic hyperplasia (BPH) patients with lower urinary tract symptoms (LUTS) is affected by the bladder wall thickness (BWT) Methods: A total of 125 male BPH patients with LUTS were enrolled. All patients were assessed using The International Prostatic Symptom Score (IPSS), prostate specific antigen (PSA), prostate volume, uroflowmetry, post voiding residual (PVR). BWT was measured by Trans-abdominal ultrasound, and patients were divided into two groups group 1 (patients with BWT <5 mm) and group 2 (patients with BWT ≥5 mm). The patients were reassessed after 2 months of treatment with α 1 receptor blocker (alfuzosin 10 mg). Clinical parameters were analyzed and compared between groups.

RESULTS

There were significant difference between both groups as regard IPSS, voiding symptoms, and storage symptoms (p = 0.005), (p = 0.010) and (p = 0.041) respectively. After medication, there were improvements in the total IPSS, voiding symptoms, storage symptoms, Qmax, PVR and Qol in both groups and these improvements were more effectively in (group 1) than (group 2) with statistically significant differences (p < 0.05).

CONCLUSION

BWT has positive correlation with the total IPSS, voiding symptoms subscores and storage symptoms subscores. The response to medical treatment is found statistically less in patients with BWT greater than 5 mm.

Solifenacin/tamsulosin fixed-dose combination therapy to treat lower urinary tract symptoms in patients with benign prostatic hyperplasia

Treatment of male lower urinary tract symptoms (LUTS) has traditionally focused on the management of benign prostatic obstruction, but the contribution of bladder dysfunction has been recently recognized. Therefore, it is well understood that LUTS have multifactorial etiology and often occur in clusters and not in isolation. Voiding LUTS are highly prevalent in men, but storage LUTS have been proved to be more bothersome. α₁-Blockers are the most widely used pharmacologic agents for the treatment of symptoms relating to benign prostatic enlargement due to benign prostatic hyperplasia (BPH), while antimuscarinics are the drug class of choice for overactive bladder symptoms. A combination of the two drug classes would be a reasonable approach to treat men with both storage and voiding symptoms, and several short-term studies have proved the efficacy and safety of different combinations with an α₁-blocker and an antimuscarinic. Following previous studies on the separate administration of solifenacin and tamsulosin, a fixed-dose combination tablet of tamsulosin oral controlled absorption system (OCAS) 0.4 mg and solifenacin succinate 6 mg has been recently introduced, and the current review evaluates the available data on the use of this fixed-dose combination in the treatment of LUTS in men with BPH.

The Effect of Systemic Tamsulosin Hydrochloride on Choroidal Thickness Measured by Enhanced Depth Imaging Spectral Domain Optical Coherence Tomography

BACKGROUND

To evaluate the effects of selective α1A-adrenoceptor antagonist tamsulosin hydrochloride on choroidal thickness using enhanced depth imaging spectral-domain optical coherence tomography (EDI-OCT).

METHODS

This is a prospective observational study including 29 eyes of 29 patients with newly diagnosed benign prostatic hyperplasia. Choroidal thickness and retrobulbar ocular blood flow measurements were performed at baseline and after 3 months of treatment. Results were analyzed by the masked observer.

RESULTS

The mean subfoveal choroidal thickness (275.8-291.9 µm) and thicknesses 750 µm nasal (257.9-270.4 µm) and 750 µm temporal (262.4-277.0 µm) to the fovea were significantly increased after 3 months of treatment (p < 0.001). No statistically significant change was found in retrobulbar ocular blood flow.

CONCLUSIONS

Tamsulosin causes a significant increase in EDI-OCT-based choroidal thickness measurements. This increase might be associated with choroidal vasodilation in consequence of blockade of sympathetic α1A-adrenoceptors, which is critical for the maintenance of vascular tone and resistance in the choroidal vascular architecture. This should be kept in mind when choroidal disease and its response to treatment are followed by EDI-OCT imaging.

Muscarinic receptor subtype mRNA expression in the human prostate: association with age, pathological diagnosis, prostate size, or potentially interfering medications?

As the prostate abundantly expresses muscarinic receptors and antagonists for such receptors are increasingly used in the treatment of men with voiding function and large prostates, we have explored an association of the mRNA expression of human M1, M2, M3, M4, and M5 receptors in human prostate with patient age, prostate size, prostate-specific antigen level, pathological diagnosis, and concomitant medication. mRNA was isolated from prostate chips of 110 consecutive patients undergoing transurethral resection of the prostate for the treatment of benign prostatic hyperplasia or prostate cancer. Expression of each of the five muscarinic receptor subtype transcripts was assessed by real-time PCR and association with patient age, prostate size, prostate-specific antigen level, pathological diagnosis, and concomitant medication were explored. M1 and M4 receptors were the most and least prevalently expressed subtypes in the human prostate, respectively. M1 receptor mRNA expression was weakly but significantly associated with prostate size (r = 0.2494, p = 0.0451), but mRNA expression of none of the five subtypes was significantly associated with age, prostate-specific antigen level, pathological diagnosis (benign prostatic hyperplasia vs. prostate cancer), or concomitant medication (5α-reductase inhibitors, α1- or β-adrenoceptor antagonists). We conclude that human prostate muscarinic receptor subtype transcripts apparently undergo only a very limited regulation by a variety of physiological, pathophysiological, or treatment factors. In light of the growing use of muscarinic receptor antagonists in men with voiding dysfunction including those with large prostates, the functional role of the weak association between M1 receptor mRNA expression and prostate size merits further investigation.

Investigating the effect of tamsulosin on the measurement of bladder wall thickness and International Prostate Symptom Score in benign prostatic hyperplasia

INTRODUCTION

According to previous studies, aging, gender, bladder volume and pathological states, such as bladder outflow obstruction, affect bladder wall thickness (BWT). The aim of this study was to evaluate the correlation between BWT and the International Prostatic Symptom Score (IPSS) in patients with benign prostatic hyperplasia (BPH) before and after tamsulosin treatment.

METHODS

In this study, 60 BPH patients were included. After obtaining informed consent, data were gathered using questionnaires to determine IPSS. After that, prostate-specific antigen was measured and a clinical examination, including a digital rectal examination, was performed for all patients. BWT was determined by transabdominal ultrasound. Finally, all patients were treated with tamsulosin (0.4 mg/day) for 2 months. After completing treatment, the IPSS and BWT were measured again and compared with the initial findings.

RESULTS

In total, 44 patients completed treatment. Patients aged 61.7 ± 9.2 years old. The mean ± standard deviation of IPSS and BWT were 14.6 ± 5.0 and 5.36 ± 1.28 mm before treatment, while they significantly (p < 0.0001) decreased to 8.2 ± 4.7 and 4.69 ± 1.23 mm, respectively, after treatment. Chi-square test showed that the decrease in BWT was significantly correlated with the improvement in IPSS (p = 0.002; r = 0.449).

CONCLUSION

After treatment with tamsulosin, patients experienced a reduction in their BWT which was significantly correlated with improvement in their IPSS. We conclude that transabdominal evaluation of BWT could be included in the follow-up assessment in BPH.

Determination of tamsulosin in human plasma by liquid chromatography/tandem mass spectrometry and its application to a pharmacokinetic study

Tamsulosin, a selective α₁-adrenoceptor antagonist, is used for the treatment of benign prostatic hyperplasia (BPH). We developed and validated a rapid, sensitive, and simplified liquid chromatography analytical method utilizing tandem mass spectrometry (LC-MS/MS) for the determination of tamsulosin in human plasma. After liquid-liquid extraction with methyl t-butyl ether, chromatographic separation of tamsulosin was achieved using a reversed-phase Luna C₁₈ column (2.0 mm × 50 mm, 5 μm particles) with a mobile phase of 10 mM ammonium formate buffer (pH 3.5)-methanol (25:75, v/v) and quantified by MS/MS detection in ESI positive ion mode. The flow rate of the mobile phase was 200 μL/min and the retention times of tamsulosin and the internal standard (IS, diphenhydramine) were 0.8 and 0.9 min, respectively. The calibration curves were linear over a range of 0.01-20 ng/mL (r>0.999). The lower limit of quantification using 500 μL of human plasma was 0.01 ng/mL. The mean accuracy and precision for intra- and inter-day validation of tamsulosin were both within acceptable limits. The present LC-MS/MS method showed improved sensitivity for quantification of tamsulosin in human plasma compared with previously described analytical methods. The validated method was successfully applied to a pharmacokinetic study in humans.

The effects of the combined use of a PDE5 inhibitor and medications for hypertension, lower urinary tract symptoms and dyslipidemia on corporal tissue tone

ED is closely associated with its comorbidities (hypertension, dyslipidemia and lower urinary tract symptoms (LUTS)). Therefore, several drugs have been prescribed simultaneously with PDE5 inhibitors. If a specific medication for ED comorbidities has enhancing effects on PDE5 inhibitors, it offers alternative combination therapy in nonresponders to monotherapy with PDE5 inhibitors and allows clinicians to treat ED and its comorbidities simultaneously. To establish theoretical basis of choosing an appropriate medication for ED and concomitant disease, we examined the effects combining a PDE5 inhibitor with representative drugs for hypertension, dyslipidemia and LUTS on relaxing the corpus cavernosum of rabbits using the organ-bath technique. The effect of mirodenafil on relaxing phenylephrine-induced cavernosal contractions was significantly enhanced by the presence of 10(-4) M losartan, 10(-6) M nifedipine, 10(-6) M amlodipine, 10(-7) M doxazosin and 10(-9) M tamsulosin (P<0.05). The maximum relaxation effects were 47.2±3.8%, 57.6±2.6%, 64.0±3.7%, 76.1±5.7% and 71.7±5.4%, respectively. Enalapril and simvastatin had no enhancing effects. The relaxation induced by sodium nitroprusside alone (39.0±4.0%) was significantly enhanced in the presence of the 10(-4) M losartan (66.0±6.0%, P<0.05). Tetraethylammonium (1 mM) significantly inhibited the enhancement effects of tamsulosin and doxazosin on mirodenafil-induced relaxation (doxazosin: 76.1±5.7% vs 45.3±2.3%; tamsulosin: 71.7±5.4% vs 48.1±3.5%). On the basis of these findings, losartan seemed to induce synergistic effects through an interaction with nitric oxide. In addition, K(+) channel activation could be one of the mechanisms for the synergistic effect of combining mirodenafil with doxazosin or tamsulosin. We believe that the combination of a PDE5 inhibitor with losartan, nifedipine, amlodipine, doxazosin or tamsulosin could be a pharmacologic strategy for simultaneously treating ED and its comorbidities and increasing response rates to PDE5 inhibitors.

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.

Population pharmacokinetics of tamsulosin hydrochloride in paediatric patients with neuropathic and non-neuropathic bladder

WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT

Tamsulosin is available on prescription as a modified release capsule in the US (Flomax), and in most European countries for the treatment of the signs and symptoms of benign prostatic hyperplasia (BPH). The pharmacokinetics of tamsulosin hydrochloride (HCl) have been extensively studied in adults, but no pharmacokinetic data for paediatrics have been published to date.

WHAT THIS STUDY ADDS

A population pharmacokinetic model of tamsulosin HCl was developed in paediatric patients. Covariate analysis revealed that body weight and alpha(1)-acid glycoprotein influenced both the apparent clearance and the apparent volume of distribution. This study confirms that there is no major difference in the pharmacokinetics of tamsulosin HCl between paediatrics (age range 2-16 years) and adults when the effect of body weight is taken into consideration.

AIMS

The main objective of this study was to characterize the population pharmacokinetics of tamsulosin hydrochloride (HCl) in paediatric patients with neuropathic and non-neuropathic bladder. A secondary objective was to compare the pharmacokinetics in paediatric patients and adults.

METHODS

Tamsulosin HCl plasma concentrations in 1082 plasma samples from 189 paediatric patients (age range 2-16 years) were analyzed with NONMEM, applying a one compartment model with first-order absorption. Based on the principles of allometry, body weight was incorporated in the base model, along with fixed allometric exponents. Covariate analysis was performed by means of a stepwise forward inclusion and backward elimination procedure. Simulations based on the final model were used to compare the pharmacokinetics with those in adults.

RESULTS

Beside the priori-implemented body weight, only alpha(1)-acid glycoprotein had an effect on both apparent clearance and apparent volume of distribution. No other investigated covariates, including gender, age, race, patient population and concomitant therapy with anti-cholinergics, significantly affected the pharmacokinetics of tamsulosin HCl (P < 0.001). The results of simulations indicated that the exposure in 12.5 kg paediatric patients was 3.5-4.3 fold higher than that in 70.0 kg adults. After a weight-based dose administration, the exposure in paediatric patients was comparable with that in healthy adults.

CONCLUSIONS

A population pharmacokinetic model of tamsulosin HCl in paediatric patients was established and it described the data well. There was no major difference in the pharmacokinetics of tamsulosin HCl between paediatric patients (age range 2-16 years) and adults when the effect of body weight was taken into consideration.

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.

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.

Functional screening of adrenergic receptors by measuring intracellular calcium using the FlexStation scanning fluorimeter

In this study we test whether functional screening of compounds to adrenergic G protein-coupled receptors (GPCRs) would provide data that correlated significantly with radiolabeled binding data, thereby permitting researchers to replace expensive radioligand-binding experiments with non-radioactive screening. An increase in intracellular calcium levels represents an important second messenger signal for several recombinant GPCRs. In this study, we describe the affinities of three alpha adrenoceptor antagonists (terazosin, tamsulosin and alfuzosin), determined by monitoring the changes in intracellular calcium levels and comparing them with their radioligand-binding affinities. In addition to determining the functional affinities of the three alpha adrenoceptor antagonists, we evaluate their binding at two alpha adrenoceptor subtypes and optimized the assay for high-throughput screening.

Subtypes of alpha1-adrenoceptors in BPH: future prospects for personalized medicine

The alpha(1)-adrenoceptors (alpha(1)-ARs) are involved in regulation of prostatic smooth muscle tone, and are a critical mediator of lower urinary tract symptoms and pathophysiology in benign prostatic hyperplasia (BPH). As a result, alpha(1)-AR antagonists are now used as first-line medical treatment for BPH. Three alpha(1)-AR subtypes (alpha(1a)-AR, alpha(1b)-AR, alpha(1d)-AR) have been identified on the basis of results of pharmacological and molecular cloning studies; however, the precise physiological role of individual alpha(1)-AR subtypes remains elusive. The expression levels of alpha(1)-AR subtypes in the prostate differ between patients, and individual differences in the genetic background of patients with BPH might be associated with variation in responses to subtype-selective alpha(1)-AR antagonists. In addition, single nucleotide polymorphism and microarray-based gene expression profiling studies might provide an opportunity to identify markers that predict clinical response and therapeutic tolerance to alpha(1)-AR antagonists. Further genomic studies will refine our knowledge of the functions of alpha(1)-AR subtypes, lead to new strategies for the clinical management of BPH and, perhaps, enable personalized treatment of BPH in the future.

Effect of dapoxetine on the pharmacokinetics and hemodynamic effects of tamsulosin in men on a stable dose of tamsulosin

The tolerability of dapoxetine, a short-acting selective serotonin reuptake inhibitor being developed for premature ejaculation, was evaluated when coadministered with tamsulosin. Adult men on a stable dose of tamsulosin were randomized to also receive dapoxetine 30 or 60 mg, or placebo, in a crossover design. Supine and standing vital signs were measured on days 1 and 7. Plasma samples were collected for measurement of tamsulosin, dapoxetine, and dapoxetine metabolites. Coadministration of dapoxetine with tamsulosin did not alter orthostatic profiles or affect the incidence of orthostatic hypotension. Tamsulosin and dapoxetine pharmacokinetics were not altered. Adverse events were reported by 5.4%, 10.9%, and 23.2% of participants receiving tamsulosin with placebo, dapoxetine 30 mg, and dapoxetine 60 mg, respectively. The most common adverse events were diarrhea, dizziness, headache, and nausea. Therefore, dapoxetine had no clinically important effects on the pharmacokinetics or orthostatic profile of tamsulosin in men on a stable tamsulosin regimen.

Tamsulosin modified release and oral controlled absorption system in the management of lower urinary tract symptoms suggestive of benign prostatic hyperplasia

BACKGROUND

Tamsulosin MR has been on the market for the treatment of lower urinary tract symptoms suggestive of benign prostatic hyperplasia (LUTS/BPH) for many years. Recently, tamsulosin OCAS was introduced, which has improved pharmacokinetics.

OBJECTIVE

To evaluate the efficacy and safety of tamsulosin.

METHODS

Literature was identified through a PubMed search using the term 'tamsulosin' and by screening reference lists of review articles.

RESULTS

Tamsulosin rapidly improves LUTS/BPH, with benefits maintained in the long-term. The overall tolerability of tamsulosin MR 0.4 mg is comparable to that of placebo. While the efficacy of tamsulosin OCAS and MR is comparable, tamsulosin OCAS is slightly better tolerated.

CONCLUSION

Tamsulosin OCAS 0.4 mg has a favourable efficacy/safety profile and should be considered the treatment of choice for patients requiring optimal symptom control without increasing the risk of cardiovascular adverse events.

Incidence of intraoperative floppy iris syndrome in patients on either systemic or topical alpha(1)-adrenoceptor antagonist

PURPOSE

To evaluate the incidence of Intraoperative Floppy Iris syndrome (IFIS) in relation to the usage of alpha(1)-adrenoceptor antagonists.

DESIGN

Prospective, interventional case series.

METHODS

In 2,643 consecutive eyes of 1,968 patients undergoing cataract surgery, occurrence of IFIS and use of alpha(1) antagonists were recorded.

RESULTS

IFIS was observed in 29 eyes (1.1%) of 25 male patients, all of whom were receiving alpha(1) antagonists. In those receiving systemic tamsulosin, alpha(1A) selective antagonist, IFIS developed in 25 (43.1%) of 58 eyes. In those receiving systemic naftopidil, alpha(1A) and alpha(1D) antagonists, IFIS was found in 4 (19.0%) of 21 eyes. There was no case of IFIS in patients who received other systemic alpha(1) antagonists and in eyes treated with bunazosin eyedrops, a nonselective alpha(1) antagonist.

CONCLUSIONS

IFIS occurred in 1.1% of cases treated with systemic alpha(1A)-adrenoceptor antagonists for benign prostatic hypertrophy. Topical nonselective alpha(1) antagonist did not induce IFIS.

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.

Signal transduction and regulation: are all alpha1-adrenergic receptor subtypes created equal?

The current manuscript reviews the evidence whether and how subtypes of alpha(1)-adrenergic receptors, i.e. alpha(1A)-, alpha(1B)- and alpha(1D)-adrenergic receptors, differentially couple to signal transduction pathways and exhibit differential susceptibility to regulation. In both regards studies in tissues or cells natively expressing the subtypes are hampered because the relative expression of the subtypes is poorly controlled and the observed effects may be cell-type specific. An alternative approach, i.e. transfection of multiple subtypes into the same host cell line overcomes this limitation, but it often remains unclear whether results in such artificial systems are representative for the physiological situation. The overall evidence suggests that indeed subtype-intrinsic and cell type-specific factors interact to direct alpha(1)-adrenergic receptor signaling and regulation. This may explain why so many apparently controversial findings have been reported from various tissues and cells. One of the few consistent themes is that alpha(1D)-adrenergic receptors signal less effectively upon agonist stimulation than the other subtypes, most likely because they exhibit spontaneous internalization.

Discontinuation of Tamsulosin Treatment in Men with Lower Urinary Tract Symptoms: A Pilot Study

OBJECTIVES

Since little investigation has been undertaken to determine if alpha1-blockers should be given continuously to sustain their efficacy, we conducted a pilot study to determine symptom change following discontinuation of tamsulosin after an initial improvement in symptoms in men with lower urinary tract symptoms (LUTS).

PATIENTS AND METHODS

Thirty-three of 78 patients with mild-to-moderate prostate hyperplasia, who had symptom improvement according to the International Prostate Symptom Score (IPSS) to <10 or the quality of life (QOL) index to < or =3 after initial treatment with tamsulosin, were enrolled in this study. Subjective parameters (IPSS and QOL index) and objective parameters (maximum and mean urinary flow rates) were evaluated at baseline and after initial treatment, and 4, 8, 12 and 24 weeks after discontinuing tamsulosin.

RESULTS

The rates of successful discontinuation of tamsulosin were high throughout the follow-up period, i.e., 80.6% at 4 weeks, 80.6% at 8 weeks, 80.0% at 12 weeks, and 68.9% at 24 weeks. Temporary worsening in both subjective and objective parameters was observed only at 4 weeks; however, these parameters recovered to almost post-treatment levels at 24 weeks.

CONCLUSION

The present study suggests that continuous treatment is not always needed to maintain urinary symptom relief in a specific subset of patients who felt symptom improvement after initial treatment with tamsulosin.

Safety and efficacy of tamsulosin in the treatment of painful ejaculation: a randomized, double-blind, placebo-controlled study

We evaluate the efficacy and safety of tamsulosin a selective alpha(1A)-receptor antagonist in patients with painful ejaculation (PE) as a sole entity. A total of 118 men with PE were included in the study. Patients were randomly assigned to receive 0.4 mg oral daily tamsulosin (group 1, n=59) or placebo (group 2, n=59), during a 6-week period for each agent. Pretreatment evaluation included history and physical examination, International Index of Erectile Function (IIEF) and a visual analog scale (VAS) for pain. The efficacy of two treatments was assessed every 2 weeks during treatment, and at the end of the study using responses to IIEF, VAS evaluation, mean intercourse satisfaction domain, mean weekly coitus episodes and adverse drug effects. In all, 104 patients (88%) completed the whole treatment schedule. Pain resolved in 16 and 13% of the patients treated with tamsulosin and placebo, respectively (P=0.1). Baseline mean intercourse satisfaction domain values of IIEF 10 and 11 reached to 12 and 10 at 6-week treatment in groups 1 and 2, respectively (P=0.08). The VAS after tamsulosin and placebo decreased from 5.7 and 5.8 to 5.1 and 5.5, respectively (P=0.1). The mean weekly intercourse episodes increased from pretreatment values of 1.8 and 1.6 to 1.9 and 1.7, for tamsulosin and placebo, respectively (P=0.08). Mean number of adverse events was 11 for tamsulosin and 5 for placebo (P<0.05). Tamsulosin is no better than placebo in improvement of PE as a sole entity.

Comparison of the Cardiovascular Effects of Tamsulosin Oral Controlled Absorption System (OCAS®) and Alfuzosin Prolonged Release (XL)

OBJECTIVE

The cardiovascular (CV) effects of tamsulosin oral controlled absorption system (OCAS) 0.4 mg were compared with those of alfuzosin prolonged release (XL) 10 mg.

METHODS

Two single-dose, crossover studies were performed. In study 1, CV alpha1-adrenoceptor antagonism was assessed by measuring the inhibition of phenylephrine (PE)-induced increases in diastolic blood pressure (DBP) and total peripheral resistance (TPR) before and after dosing with placebo, tamsulosin OCAS, and alfuzosin XL in 18 young subjects. In study 2, orthostatic stress tests (OTs) were performed before and after dosing with tamsulosin OCAS and alfuzosin XL in 40 elderly subjects. Pharmacokinetics were assessed in both studies.

RESULTS

In study 1, tamsulosin OCAS induced statistically significantly less inhibition of PE-induced increases in DBP at 2 h after dosing and in TPR at 2 and 4 h after dosing than alfuzosin XL. In study 2, tamsulosin OCAS had a lower incidence of positive OTs than did alfuzosin XL, with the difference between both treatments being statistically significant at 6h after dosing and for all time points after dosing combined. This was in line with smaller changes in vital signs observed for tamsulosin OCAS. The t(max) values for both treatments were comparable.

CONCLUSIONS

Tamsulosin OCAS 0.4 mg produces smaller vascular effects than does alfuzosin XL 10 mg.

In vivo studies on the effects of α1-adrenoceptor antagonists on pupil diameter and urethral tone in rabbits

Alpha1-adrenoceptors mediate contraction of iris dilator smooth muscle and hence pupil dilatation. We compared the ability of i.v. bolus injections of alfuzosin, doxazosin, naftopidil, prazosin, tamsulosin and terazosin to antagonise phenylephrine-induced mydriasis relative to their potency for inhibiting phenylephrine-induced elevations of intraurethral pressure (IUP) in rabbits. Moreover, we compared the ability of these drugs to induce miosis in conscious rabbits in the absence of phenylephrine. All antagonists inhibited the effects of phenylephrine on pupil size and IUP, and the ratio of the respective ED50 values was close to unity in all cases. The doses required to induce statistically significant miosis in the absence of phenylephrine were 30- to 100-fold higher than those inhibiting phenylephrine-induced mydriasis for all antagonists, except for naftopidil. Moreover, the miotic effects of all alpha1-adrenoceptor antagonists were fully reversible within 8 h. We conclude that alfuzosin, doxazosin, naftopidil, prazosin, tamsulosin and terazosin inhibit phenylephrine-induced mydriasis in the same dose range as they inhibit elevations in IUP. Higher doses of all antagonists are required to induce miosis in the absence of an exogenous agonist, and such miosis is always reversible within hours.

Effect of D-004, a lipid extract from the Cuban royal palm fruit, on in vitro and in vivo effects mediated by alpha-adrenoceptors in rats

BACKGROUND

Benign prostatic hyperplasia (BPH) is the non-malignant, uncontrolled growth of glandular and stromal elements of the prostate gland. Lipid extracts from Saw palmetto (Arecaceae) fruits are widely used to treat BPH. The Cuban royal palm (Roystonea regia) is a member of the same family. Previous studies have found that D-004, a lipid extract from the R. regia fruit, administered orally at 200-800 mg/day for 14 days, prevented testosterone- but not dihydrotestosterone-induced prostate hyperplasia in rats.

OBJECTIVE

To determine whether D-004 can inhibit noradrenaline (NA) [norepinephrine]- and acetylcholine (ACh)-induced smooth muscle contraction in rat vas deferens and to investigate the in vivo effects of D-004 on NA pressure-elevating effects in rats, an effect mediated by vascular alpha1-adrenoceptors.

METHODS

In vitro effects were investigated by adding D-004 (125-500 microg/mL) to preparations of rat vas deferens suspended in an organ bath containing Tyrode's solution, in which in vitro contractions were induced by NA or ACh. Negative and positive controls containing Tyrode's solution alone or with Saw palmetto extracts (125-500 microg/mL), respectively, were included. To assess the in vivo effects of D-004 on arterial blood pressure, rats were randomly distributed to one of five groups (ten rats/group): these consisted of a negative control group receiving the vehicle, two groups treated with D-004 (400 and 800 mg/kg) and two other groups treated with Saw palmetto (400 and 800 mg/kg). All treatments were orally administered. Rats were anaesthetised with sodium thiopental. Heart rate and blood pressure were registered in baseline conditions. Immediately afterwards, rats were injected intravenously over 5 seconds with successive doses of NA (1, 2 and 4 microg/kg) [0.1mL/100g], with 5 minutes' interval between doses.

RESULTS

D-004 and Saw palmetto (125-500 microg/mL) significantly (p < 0.05) and dose dependently inhibited contractions induced by NA in rat vas deferens versus control. D-004 was more effective in inhibiting NA-induced contractions than Saw palmetto. The contractions induced by NA in preparations with D-004 (500 microg/mL) were weaker (p < 0.05) than in preparations containing Saw palmetto (500 microg/mL). At 125 microg/mL, D-004 inhibited the contractions induced by NA 1 and 32 x 10(-6) mol/L by 70.8% and 28.5%, respectively, and Saw palmetto by 56.2% and 10.7%, respectively. At 500 microg/mL, D-004 inhibited these contractions by 100.0% and 71.3%, and Saw palmetto by 80.0% and 42.7%, respectively. The inhibitory concentrations of 50% (IC50) for NA contractions were 148.34 (D-004) and 188.38 (Saw palmetto) microg/mL. D-004 and Saw palmetto significantly (p < 0.05) and to a similar extent inhibited ACh-induced contractions, but less effectively than contractions induced by NA, since at 125 microg/mL they were ineffective. At a dose of 800 mg/kg, but not at 400 mg/kg, D-004 and Saw palmetto inhibited the pressure-elevating effects induced with low (1 microg/kg) but not with high doses (2 and 4 microg/kg) of NA.

CONCLUSIONS

D-004 and Saw palmetto extracts inhibited in vitro the contractile responses to NA and ACh in rat vas deferens, and were more effective in inhibiting NA than ACh contractions. The in vivo effects of D-004 and Saw palmetto on the hypertensive response induced by NA were significant but modest. These results are preliminary as the relevance of the effects of D-004 on alpha1-adrenoceptors deserves further investigation, including comparative studies versus specific defined alpha1-adrenoceptor antagonists.

Effect of D-004, a Lipid Extract from the Cuban Royal Palm Fruit, on Atypical Prostate Hyperplasia Induced by Phenylephrine in Rats

BACKGROUND AND OBJECTIVE

Benign prostatic hyperplasia (BPH) is a non-malignant enlargement of the prostate that results in obstructive lower urinary tract symptoms. Saw palmetto (Serenoa repens), the dwarf American palm (Arecaceae family), is commonly used to treat BPH. The Cuban royal palm (Roystonea regia) also belongs to the Arecaceae family, and 200-400mg of D-004, a lipid extract from its fruits, administered orally for 14 days has been shown to prevent testosterone- but not dihydrotestosterone-induced prostatic hyperplasia in rats. D-004 (125-250 microg/mL) added to preparations of rat vas deferens caused a marked, dose-dependent and significant inhibition of noradrenaline-induced smooth muscle contraction, a response mediated through alpha(1)-adrenoceptors, and was more effective in these respects than Saw palmetto. However, the in vivo effects of D-004 and Saw palmetto on the hypertensive response induced by noradrenaline were modest (albeit significant), and neither treatment affected resting blood pressure or heart rate in rats. The differential effects of D-004 in in vitro and in vivo models could be related to a differential affinity for adrenoceptor subtypes or to different bioavailabilities in vascular and urogenital targets. Phenylephrine injected into rodents induces prostatic hyperplasia with all the characteristic morphological changes of the condition but does not result in enlargement of the prostate. Therefore, this phenylephrine-induced change in rat prostate tissue is called atypical prostatic hyperplasia. It serves as an in vivo model of prostatic hyperplasia induced by stimulation of alpha(1)-adrenoceptors. The objective of this study was to determine whether D-004 can inhibit induction of atypical prostatic hyperplasia by phenylephrine in rats.

METHODS

Rats were randomly distributed into five groups (ten rats/group). One group was a negative control and received oral vehicle only. The other four groups were injected subcutaneously with phenylephrine (2 mg/kg): of these groups, one was a positive control receiving the vehicle, and the other three groups were treated with D-004 or Saw palmetto (both 400 mg/kg) or tamsulosin 0.4 mg/kg. All active treatments were given orally for 28 days. After completion of treatment, rats were placed unrestrained in metabolic cages and micturition studies were performed. The rats were later killed and their prostates removed and weighed. Prostate samples were processed for histological study, with histological changes being assessed according to a scoring system. Bodyweight was measured at baseline and at weekly intervals.

RESULTS

Histological examination of positive control rats revealed features of atypical prostatic hyperplasia, with piling-up, papillary and cribiform patterns and budding-out of epithelial cells. Micturition assessment revealed that phenylephrine significantly lowered both the total volume of urine in 1 hour and the volume per micturition; the latter was considered the main efficacy variable. D-004 and Saw palmetto extracts significantly prevented this reduction in volume per micturition by 70.5% and 68.6%, respectively, while tamsulosin totally abolished the reduction in micturition induced by phenylephrine (100% inhibition). Tamsulosin, D-004 and Saw palmetto significantly reduced the histological changes of atypical prostatic hyperplasia induced by phenylephrine by 73.1%, 61.2% and 50.0%, respectively.

CONCLUSIONS

Administration of D-004 resulted in marked and significant prevention of phenylephrine-induced impairment of micturition and histological changes in rat prostate. These findings indicate that, in vivo, D-004 effectively opposes these responses to phenylephrine, which are mediated through urogenital alpha(1)-adrenoceptors. In this respect, D-004 was moderately more effective than Saw palmetto, a phytotherapeutic standard used to treat BPH, but less effective than tamsulosin, a selective alpha(1A)-adrenoceptor antagonist.

The Vasodilatory Effect of Alfuzosin and Tamsulosin in Passive Orthostasis: A Randomised, Double-Blind, Placebo-Controlled Study

OBJECTIVE

To compare in details the effects of urologically used alpha(1)-blockers alfuzosin and tamsulosin on the cardiovascular responses to passive orthostasis.

METHODS

The responses to passive orthostasis (tilt provocation at 60 degrees for 8 min) were measured in normotensive healthy volunteers with finger blood pressure method and whole-body impedance cardiography prior to the administration of the drugs as well as three days after the beginning of the randomised, double-blind medications. The parallel treatments were standard clinically used doses of alpha(1)-blockers alfuzosin (5 mg twice daily, n=10), tamsulosin (0.4 mg once daily, n=10), or placebo (n=11).

RESULTS

When measured prior to the head-up tilt test in supine position, neither alfuzosin nor tamsulosin significantly changed any of the cardiovascular variables. During the passive orthostasis, however, both tamsulosin and alfuzosin reduced systemic vascular resistance index compared to pre-drug responses (-540 and -462 dyns/cm(5)m(2), respectively, p<0.05). Both drugs also augmented orthostatic responses of heart rate (11 and 9 bpm, respectively, p<0.05) and cardiac index (0.50 and 0.40 l/min/m(2), respectively, p<0.05) but not those of stroke index when compared to the responses during placebo or before the administration of the drugs. The alfuzosin and tamsulosin groups did not significantly differ from each other in terms of any parameter.

CONCLUSIONS

Both alfuzosin and tamsulosin have clear cardiovascular effects, which are most strikingly evident in the influences on systemic vascular resistance and cardiac output.

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.

Tamsulosin: a review of its pharmacology and therapeutic efficacy in the management of lower urinary tract symptoms

Tamsulosin is a subtype-selective alpha(1A)- and alpha(1D )-adrenoceptor antagonist. alpha(1)-Receptors predominate in the prostate gland, prostatic capsule, prostatic urethra and bladder, and the relaxation of prostate and bladder smooth muscles is associated with improved maximal urine flow (Q(max)) and alleviation of lower urinary tract symptoms (LUTS) in patients with benign prostatic hyperplasia (BPH). Tamsulosin 0.4 mg once daily in a modified-release formulation increased Q(max) and improved symptom scores relative to baseline to a greater extent than placebo in 12- and 13-week double-blind, randomised, multicentre, clinical trials in patients with LUTS, with statistical significance between treatments for Q(max) values in two of three published US and European studies. Tamsulosin is effective in patients with mild to severe LUTS associated with BPH, in patients with diabetes mellitus and in the elderly, and does not interfere with concomitant antihypertensive therapy. Pooled data based on patients receiving tamsulosin 0.4 or 0. 8mg once daily indicate maintenance of efficacy for up to 6 years. Tamsulosin 0.4 mg once daily was of similar efficacy to alfuzosin 2.5 mg three times daily, with less tendency to cause hypotensive effects, in a double-blind, randomised 12-week trial. Benefit of the drug has also been shown in patients with acute urinary retention or chronic abacterial prostatitis, those receiving high energy transurethral microwave thermotherapy, and in patients with prostate cancer with radiation-induced urethritis. Dizziness and abnormal ejaculation are stated to be the most common adverse events, with asthenia, postural hypotension and palpitations being seen less frequently (1 to 2% incidence), in patients receiving tamsulosin 0.4 mg once daily. Tamsulosin has not been associated with clinically significant changes in blood pressure in clinical trials.

CONCLUSION

The alpha(1A)- and alpha(1D)-adrenoceptor antagonist tamsulosin, given at a dosage of 0.4 mg once daily in a modified-release formulation, is effective and well tolerated in the treatment of LUTS associated with BPH. Although the drug has been directly compared to date with one other agent only, data show overall that tamsulosin clearly offers advantages over other alpha(1)-adrenoceptor antagonists in terms of the need for a single daily dose only, and its low potential for hypotensive effects or interference with concomitant antihypertensive therapy. Dosage titration at the start of treatment is not necessary. Tamsulosin has a rapid onset of action and is effective in patients with moderate or severe symptoms. The drug is therefore a valuable therapeutic option, with both demonstrated and potential advantages over older nonselective agents, in the management of patients with LUTS associated with BPH.

Tamsulosin: an update of its role in the management of lower urinary tract symptoms

Tamsulosin is a selective alpha1A- and alpha1D-adrenoceptor antagonist. These alpha1-receptors are predominant in the prostate, prostatic capsule, prostatic urethra and bladder. The relaxation of prostate and bladder smooth muscles may result in improvement in maximum urine flow (Qmax) and reduction of lower urinary tract symptoms (LUTS). Tamsulosin 0.4 and 0.8 mg/day in a modified-release formulation was significantly more effective than placebo in large (n >250) double-blind, randomised, multicentre, 12- to 13- week clinical trials in patients with LUTS. A greater increase in Qmax from baseline was seen in patients receiving tamsulosin 0.4 or 0.8 mg/day (1.4 to 1.79 ml/sec from a baseline of 9.46 to 10.7 ml/sec) than in placebo recipients (0.4 to 0.93 ml/sec from a baseline of 9.75 to 10.4 ml/sec); the between-group difference was significant in two of three studies. Tamsulosin 0.4 or 0.8 mg/day improved total Boyarsky symptom scores from baseline by a significantly greater extent (by 3.0 to 5.2 points from a baseline of 9.5 to 11.1 points) than placebo (1.9 to 3.2 points from a baseline of 9.3 to 11.0 points). In noncomparative extension studies, the improvement in efficacy parameters with tamsulosin treatment was maintained for up to 4 years. Tamsulosin is effective in patients with mild to severe LUTS, patients with diabetes mellitus or those aged > or = 65 years and does not interfere with the antihypertensive action of nifedipine, enalapril or atenolol. Tamsulosin 0.4 mg/day for 12 weeks and tamsulosin 0.2 mg/day for 4 weeks were as effective as alfuzosin 2.5mg three times daily and terazosin 2 mg/day, respectively, in improving Qmax and symptom scores in randomised comparative trials. With the exception of a numberically greater incidence of abnormal ejaculation, dizziness and rhinitis, the incidence of adverse events with tamsulosin 0.4 mg/day was similar to that seen with placebo in randomised, double-blind studies. The overall incidence of symptoms indicative of orthostasis was 1.4% with tamsulosin 0.4 or 0.8 mg/day treatment. Tamsulosin had less effect on blood pressure than alfuzosin or terazosin.

CONCLUSION

Tamsulosin, an alpha1-adrenoceptor antagonist, has a well established place in the treatment of LUTS and has a tolerability profile similar to that of placebo (apart from a higher incidence of abnormal ejaculation, dizziness and rhinitis). Comparative data have shown tamsulosin to be as effective as other alpha1-adrenoceptor antagonists at increasing Qmax and improving symptom scores. However, tamsulosin is unlikely to produce orthostatic hypotensive adverse effects or interfere with concomitant antihypertensive drug therapy. Therefore, tamsulosin is a useful therapeutic option in the management of patients with moderate to severe LUTS.

Novel heterocycles as selective alpha1-adrenergic receptor antagonists

A novel series of aryl piperazine substituted heterocycles has been synthesized and identified as antagonists of the alpha1a-adrenergic receptor (alpha1a-AR), which has been implicated in benign prostatic hyperplasia (BPH). These compounds selectively inhibit binding to the alpha1a-AR with K(i)s as low as 2.1 nM.

The autonomic and sensory innervation of the smooth muscle of the prostate gland: a review of pharmacological and histological studies

1. We review literature demonstrating (a) the presence and (b) the actions of substances that mediate or modify neuroeffector transmission to the smooth muscle of the prostrate stroma of a number of species including man. 2. In all species studied prostatic stroma, but not secretory acini, receives rich noradrenergic innervation. Stimulation of these nerves causes contractions of prostate smooth muscle that are inhibited by guanethidine and by alpha1-adrenoceptor antagonists that probably act at the alpha1L-adrenoceptor. Such actions underlie the clinical use of alpha1-adrenoceptor antagonists in benign prostatic hyperplasia (BPH). 3. Acetylcholinesterase-positive nerves innervate prostatic stroma as well as epithelium. Atropine reduces nerve-mediated contractions of stromal muscle in the rat, guinea-pig and rabbit. M1, M2 and M3 muscarinic receptors have been implicated in eliciting or facilitating contraction in the prostate from guinea-pig, dog and rat, respectively. 4. Adenine nucleotides and nucleosides, nitric oxide (NO), opioids, neuropeptide Y (NPY) and vasoactive intestinal peptide (VIP) may act as co-transmitters or modulators in autonomic effector nerves supplying prostate stroma. Adenosine inhibits neurotransmission to the rat prostate, and NO is inhibitory in prostate from human, rat, rabbit, pig and dog. The activity of peptides present in the relatively sparse sensory innervation of the prostate exhibits species variation, but, when effective, calcitonin gene-related peptide is inhibitory while tachykinins are stimulant. The roles of NPY and VIP in modulating stromal contractility remain unclear. 5. Taken together the current literature indicates that, in addition to noradrenaline, other neurotransmitters and neuromodulators may regulate the tone of prostatic smooth muscle. Whether drugs that mimic or modify their actions might be useful in providing symptomatic relief of the urinary symptoms associated with BPH remains to be established.