Pharmacological evidence of distinct alpha 1-adrenoceptor subtypes mediating the contraction of human prostatic urethra and peripheral artery

Efficacy and tolerability of drugs for treatment of benign prostatic hyperplasia

It has long been recognised that neural factors are of considerable importance in lower urinary tract function. Whilst reduction in the bulk of the human prostate is feasible, experience on this therapeutic approach proved to be disappointing. Existing trial data with the agent finasteride are reviewed. A number of formulations derived from plant extracts have been advocated but their mechanism of action remain largely obscure and there is a dearth of placebo controlled information to support their efficacy. Experience over the last 10 years has demonstrated efficacy with the use of alpha adrenoceptor blockade in the management of BPH. Alpha adrenoceptor antagonists relax the prostatic smooth muscle by interrupting the sympathetic pathway at the receptor level. Recent developments in this field include the recognition that there are alpha I adrenoceptor subtypes. The functional adrenoceptor in the human prostate is predominantly the alpha IA - subtype. Of the alpha 1-adrenoceptor antagonists only tamsulosin discriminates between the alpha 1-adrenoceptor subtypes. Alpha 1-blockers should be used in first-line medical therapy for BPH and 5-alpha-reductase inhibitors reserved for those patients in whom alpha-blocker therapy fails. Alpha I-blockers such as doxazosin, tamsulosin, terazosin, alfuzosin are effective in the treatment of BPH both in younger and in older men. The drugs are well tolerated. The majority of side effects were classified as minor and mild. The most common complaints, as with other alpha-blockers, are dizziness, fatigue and headache, and these are often transient. In contrast, finasteride can lead to impotence, reduced libido. gynaecomastia or ejaculatory disorders. Men with small prostates may not be suitable candidates for finasteride therapy.

alpha(1)-Adrenoceptor subtypes in the mouse mesenteric artery and abdominal aorta

1. Subtypes of alpha(1)-adrenoceptor-mediated contractions to noradrenaline in mouse mesenteric artery and abdominal aorta were examined. 2. In mesenteric artery, BMY7378, 5-methylurapidil, WB4101 and prazosin were inhibited contraction to noradrenaline The good correlation for pA(2) values of antagonists in native alpha(1D)- (rat thoracic aorta) adrenoceptor subtype and pK(i) values in rat cloned alpha(1d)-adrenoceptor with the pA(2) values estimated in the mouse mesenteric artery was obtained. However, the pA(2) value for BMY7378 is significantly lower than the accepted value against the alpha(1D)-adrenoceptor subtype. 3. In the abdominal aorta, it was obtained the regional difference for the sensitivity for noradrenaline. 4. In the upper abdominal aorta, the good correlation for the pA(2) values of the antagonists in the native alpha(1D)-adrenoceptor subtype and pK(i) values in the cloned alpha(1d)-adrenoceptor with the pA(2) values estimated in the upper abdominal aorta was obtained, and regression line was close to the line of identity. 5. In the lower abdominal aorta, the good correlation for the reported pK(i) values in the cloned alpha(1a)-adrenoceptor subtype with the pA(2) values estimated in the mouse lower abdominal aorta was obtained, and regression line was close to the line of identity. 6. In conclusion, the present functional data in the mouse suggest that (1) alpha(1D)-like adrenoceptors are present in the mesenteric artery, (2) there is the regional difference for the sensitivity for noradrenaline in the abdominal aorta and (3) noradrenaline evokes the contraction mediated through alpha(1D)-adrenoceptor in the upper abdominal aorta, whereas there is alpha(1A)-adrenoceptor-mediated contraction in the lower abdominal aorta.

Characterization of alpha1-adrenoceptor-mediated contraction in the mouse thoracic aorta

In the mouse thoracic aorta, noradrenaline, adrenaline, phenylephrine and methoxamine behaved as full agonists. The pA(2) values for 8-[2-[4-(2-methoxyphenyl)-1-piperazinyl]ethyl]-8-azaspiro[4,5]decane-7,9-dione dihydrochloride (BMY 7378) against each agonist were in good agreement with the generally accepted affinity value of alpha(1D)-adrenoceptors. 5-Methylurapidil, 2-[2,6-dimethoxyphenoxyethyl]aminomethyl-1,4-benzodioxane hydrochloride (WB 4101) and prazosin inhibited the contraction in response to noradrenaline. A significant correlation was obtained between the antagonist affinities in mouse thoracic aorta and those of native alpha(1D)-adrenoceptors in rat thoracic aorta or with those of cloned alpha(1d)-adrenoceptors, but not with those for either alpha(1a)- or alpha(1b)-adrenoceptors. Buspirone behaved as a partial agonist in mouse thoracic aorta, the contraction of which was antagonized by BMY 7378 with a pA(2) value (8.49) consistent with that found against noradrenaline (8.43). Clonidine acted as a partial agonist (pD(2)=5.94). The pK(p) value for clonidine against noradrenaline was similar to the pD(2) value for clonidine. The apparent pK(B) value for BMY 7378 against clonidine was similar to the pA(2) value against other full agonists used in the present study. These results suggest that the alpha(1D)-adrenoceptor subtype exists, and that the full agonists and the partial agonists evoke the contraction mediated through the alpha(1D)-adrenoceptor in mouse thoracic aorta.

Functional characterization of alpha(1)-adrenoceptor subtypes in human skeletal muscle resistance arteries

alpha(1)-adrenoceptor subtypes in human skeletal muscle resistance arteries were characterized using agonists noradrenaline (non-selective) and A61603 (alpha(1A)-selective), the antagonists prazosin (non-selective), 5-methyl-urapidil (alpha(1A)-selective) and BMY7378 (alpha(1D)-selective) and the alkylating agent chloroethylclonidine (preferential for alpha(1B)). Small arteries were obtained from the non-ischaemic skeletal muscle of limbs amputated for critical limb ischaemia and isometric tension recorded using wire myography. Prazosin antagonized responses to noradrenaline with a pA(2) value of 9.18, consistent with the presence of alpha(1)-adrenoceptors, although the Schild slope (1.32) was significantly different from unity. 5-Methyl-urapidil competitively antagonized responses to noradrenaline with a pK(B) value of 8.48 and a Schild slope of 0.99, consistent with the presence of alpha(1A)-adrenoceptors. In the presence of 300 nM 5-methyl-urapidil, noradrenaline exhibited biphasic concentration response curves, indicating the presence of a minor population of a 5-methyl-urapidil-resistant subtype. Contractile responses to noradrenaline were not affected by 1 microM chloroethylclonidine suggesting the absence of alpha(1B)-adrenoceptors. Maximum responses to noradrenaline and A61603 were reduced to a similar extent by 10 microM chloroethylclonidine, suggesting an effect of chloroethylclonidine at alpha(1A)-adrenoceptors at the higher concentration. BMY7378 (10 and 100 nM) had no effect on responses to noradrenaline. BMY7378 (1 microM) poorly shifted the potency of noradrenaline giving a pA(2) of 6.52. These results rule out the presence of the alpha(1D)-subtype. These results show that contractile responses to noradrenaline in human skeletal muscle resistance arteries are predominantly mediated by the alpha(1A)-adrenoceptor subtype with a minor population of an unknown alpha(1)-adrenoceptor subtype.

Alpha adrenoceptor antagonists in the year 2000: is there anything new?

Selective alpha1-adrenergic blockade is now a well accepted and widely used therapeutic treatment for patients presenting with symptomatic bladder outlet obstruction thought to be associated with benign prostatic hyperplasia. This review summarizes the recent developments in this field relating to the subject of receptor subtype selectivity and the potential relevance of this to clinical usefulness of existing drug therapy. Whilst a number of unanswered questions remain as to the exact mechanisms of both drug action and side-effect profile, nevertheless it is clear that existing clinically available alpha1-antagonists provide a safe, effective and generally well tolerated therapy for patients with lower urinary tract symptoms thought to be associated with benign prostatic obstruction. The implications of the ALLHAT study are discussed.

Endogenous circulating sympatholytic factor in orthostatic intolerance

Sympathotonic orthostatic hypotension (SOH) is an idiopathic syndrome characterized by tachycardia, hypotension, elevated plasma norepinephrine, and symptoms of orthostatic intolerance provoked by assumption of an upright posture. We studied a woman with severe progressive SOH with blood pressure unresponsive to the pressor effects of alpha(1)-adrenergic receptor (AR) agonists. We tested the hypothesis that a circulating factor in this patient interferes with vascular adrenergic neurotransmission. Preincubation of porcine pulmonary artery vessel rings with patient plasma produced a dose-dependent inhibition of vasoconstriction to phenylephrine in vitro, abolished vasoconstriction to direct electrical stimulation, and had no effect on nonadrenergic vasoconstrictive stimuli (endothelin-1), PGF-2alpha (or KCl). Preincubation of vessels with control plasma was devoid of these effects. SOH plasma inhibited the binding of an alpha(1)-selective antagonist radioligand ([(125)I]HEAT) to membrane fractions derived from porcine pulmonary artery vessel rings, rat liver, and cell lines selectively overexpressing human ARs of the alpha(1B) subtype but not other AR subtypes (alpha(1A) and alpha(1D)). We conclude that a factor in SOH plasma can selectively and irreversibly inhibit adrenergic ligand binding to alpha(1B) ARs. We propose that this factor contributes to a novel pathogenesis for SOH in this patient. This patient's syndrome represents a new disease entity, and her plasma may provide a unique tool for probing the selective functions of alpha(1)-ARs.

Design, synthesis and biological evaluation of pyridine-phenylpiperazines: a novel series of potent and selective alpha1a-adrenergic receptor antagonist

Beginning from the screening hit and literature alpha1-adrenergic compounds, a hybridized basic skeleton A was proposed as the pharmacophore for potent and selective alpha1a-AR antagonists. Introduction of a hydroxy group to increase the flexibility afforded B which served as the screening model and resulted in the identification of the second-generation lead 1. Using the Topliss approach, a number of potent and selective alpha1a-AR antagonists were discovered. In all cases, binding affinity and selectivity at the alpha1a-AR of S-hydroxy enantiomers were higher than the R-hydroxy enantiomers. As compared to the des-hydroxy analogues, the S-hydroxy enantiomers displayed comparable potency and better selectivity at alpha1a-AR. The S-hydroxy enantiomer 17 (Ki = 0.79 nM; alpha1b/alpha1a = 800; alpha1d/alpha1a = 104) was slightly less potent but much more selective at alpha1a-AR than tamsulosin (Ki = 0.13 nM, alpha1b/alpha1a = 15, alpha1d/alpha1a = 1.4). Compound 17 displayed higher selectivity in inhibiting rat prostate contraction over rat aorta contraction and also exhibited a higher degree of uroselectivity than tamsulosin in the anesthetized dog model.

The clinical role of alpha-blockers in the treatment of benign prostatic hyperplasia

Benign prostatic hyperplasia (BPH) is a highly prevalent condition that represents a significant health problem, which is likely to worsen as the population continues to age. alpha-1 adrenoceptor antagonists have been used in the treatment of this condition for well over 20 years and much is now known about their effects on the urinary tract. As these drugs have improved, their use as a first line treatment option in patients with lower urinary tract symptoms (LUTS), secondary to BPH, has continued to increase. This review details some of the background and rationale for the use of these drugs and, using the available information, compares their efficacy and tolerability profiles.

Design, synthesis, and structure-activity relationships of phthalimide-phenylpiperazines: a novel series of potent and selective alpha(1)(a)-adrenergic receptor antagonists

Beginning from the screening hit and literature alpha(1)-adrenergic compounds, a hybridized basic skeleton A was proposed as the pharmacophore for potent and selective alpha(1a)-AR antagonists. Introduction of a hydroxy group to increase the flexibility afforded B which served as the screening model and resulted in the identification of the second-generation lead 1. Using the Topliss approach, a number of potent and selective alpha(1a)-AR antagonists were discovered. In all cases, binding affinity and selectivity at the alpha(1a)-AR of S-hydroxy enantiomers were higher than those of the R-hydroxy enantiomers. As compared to the des-hydroxy analogues, the S-hydroxy enantiomers had slightly lower binding affinity at alpha(1a)-AR but gained more than 2-fold selectivity for alpha(1a)-AR over alpha(1b)-AR, and 2- to 6-fold selectivity for alpha(1a)-AR over alpha(1d)-AR. They also had less cross activities against a panel of 25-35 peripheral and CNS receptors. The S-hydroxy enantiomers 23 and 24 (K(i) = 0.29 nM, 0.33 nM; alpha(1b)/alpha(1a) >5690, >6060; alpha(1d)/alpha(1a) = 186, 158, respectively) were slightly less potent but much more selective at alpha(1a)-AR than tamsulosin (K(i) = 0.13 nM, alpha(1b)/alpha(1a) = 14.8, alpha(1d)/alpha(1a) = 1.4). In the functional assay, the S-hydroxy enantiomers 20, 23, and 24 were less potent than tamsulosin in inhibiting contractions of rat prostate tissue but more selective in the inhibition of tissue contractions of rat prostate versus rat aorta. Compound 24 was selected as the development candidate for the treatment of BPH.

Distribution of alpha1-adrenoceptor subtype mRNA and identification of subtype responsible for renovascular contraction in human renal artery

This study was intended to quantify the amounts of the alpha1-adrenoceptor subtype mRNAs in human renal artery and to demonstrate the distribution of receptor subtypes responsible for the contraction of the renal artery. RNase protection assay showed that the mean amount of alpha1a mRNA was much greater than that of alpha1b or alpha1d mRNAs in both the main and branch renal arteries. However, the abundance of alpha1a mRNA in human renal artery was much less than in our previous data in the prostate. In situ hybridization showed that all alpha1 subtype mRNAs were localized in the smooth muscle cells of the tunica media of the artery, and the distribution pattern of these three mRNAs in the main artery was the same as in the branch artery. However, the intensity of signals for alpha1d and alpha1b antisense RNAs probes was lower than that for the alpha1a antisense RNA probe. In the functional study, concentration-response curves to noradrenaline pretreated with KMD-3213, an alpha1A/L-adrenoceptor selective antagonist, seemed to be biphasic in nature. Chloroethyclonidine (CEC) failed to inactivate the noradrenaline-induced contraction, and prazosin showed relatively low affinity with a pA2 value of 8.8. These data suggest that the alpha1A/L-adrenoceptor mediates primarily those responses to noradrenaline in this artery. The other alpha1-adrenoceptor subtypes could also mediate the secondary contractile response to noradrenaline in this artery.

Subtype specific regulation of human vascular alpha(1)-adrenergic receptors by vessel bed and age

BACKGROUND

alpha(1)-adrenergic receptors (alpha(1)ARs) regulate blood pressure, regional vascular resistance, and venous capacitance; the exact subtype (alpha(1a), alpha(1b), alpha(1 d)) mediating these effects is unknown and varies with species studied. In order to understand mechanisms underlying cardiovascular responses to acute stress and chronic catecholamine exposure (as seen with aging), we tested two hypotheses: (1) human alpha(1)AR subtype expression differs with vascular bed, and (2) age influences human vascular alpha(1)AR subtype expression.

METHODS AND RESULTS

Five hundred vessels from 384 patients were examined for alpha(1)AR subtype distribution at mRNA and protein levels (RNase protection assays, ligand binding, contraction assays). Overall vessel alpha(1)AR density is 16+/-2.3fmol/mg total protein. alpha(1a)AR predominates in arteries at mRNA (P<0.001) and protein (P<0.05) levels; all 3 subtypes are present in veins. Furthermore, alpha(1)AR mRNA subtype expression varies with vessel bed (alpha(1a) higher in splanchnic versus central arteries, P<0.05); competition analysis (selected vessels) and functional assays demonstrate alpha(1a) and alpha(1b)-mediated mammary artery contraction. Overall alpha(1)AR expression doubles with age (<55 versus > or = 65 years) in mammary artery (no change in saphenous vein), accompanied by increased alpha(1b)>alpha(1a) expression (P< = 0.001).

CONCLUSIONS

Human vascular alpha(1)AR subtype distribution differs from animal models, varies with vessel bed, correlates with contraction in mammary artery, and is modulated by aging. These findings provide potential novel targets for therapeutic intervention in many clinical settings.

Contractile responses to alpha1-adrenoceptor agonists in isolated human male and female urethra

OBJECTIVE

To investigate the contractile responses mediated through alpha1-adrenoceptors in human urethra and to evaluate the effectiveness of NS-49 [(R)-(-)-3'-(2-amino-1-hydroxyethyl)-4'-fluoromethanesulphonanilide++ + hydrochloride], a novel alpha1-adrenoceptor agonist, against contraction of the human urethra.

MATERIALS AND METHODS

The contractile responses were assessed in 10 male prostatic urethrae and six female urethrae. Antagonism was evaluated in the urethra using phenylephrine, a nonselective alpha1-adrenoceptor agonist, cumulatively applied > 20 min after applying 0.1 micromol/L prazosin or 0.1 micromol/L 5-methylurapidil, a selective alpha1A-adrenoceptor antagonist. Agonism was determined in both male and female urethrae to obtain the concentration-response curve for the agonist.

RESULTS

Phenylephrine caused both male and female urethrae to contract, and showed high potency and efficacy. Prazosin antagonized these contractions with low affinity (apparent pKB of 8.30 in male urethrae). 5-Methylurapidil, also antagonized the contractions with low affinity (apparent pKB of 7.88 in male urethrae). Noradrenaline and phenylephrine caused both male and female urethrae to contract, with high potency and efficacy. A novel and selective alpha1A-and alpha1L-adrenoceptor agonist, NS-49, induced contractile responses with high potency and moderate efficacy, whereas methoxamine induced contractions with low potency and moderate efficacy. Norephedrine was a very weak contractile agonist.

CONCLUSION

In the human urethra, phenylephrine-induced contractions were mediated through alpha1L-adrenoceptors and not through alpha1A-adrenoceptors. Contractions of the human urethra induced by NS-49 were also mediated mainly through alpha1L-adrenoceptors, with high potency and moderate efficacy. NS-49 may therefore be useful for the treatment of urinary stress incontinence, with minimal side-effects because it has subtype selectivity.

Characterization of alpha1-adrenoceptor subtypes mediating noradrenaline-induced contraction of rat epididymal vas deferens in calcium-free medium

The alpha1-adrenoceptor subtype mediating noradrenaline (NA)-induced contractions of rat epididymal vas deferens in Ca2+-free/EGTA (1 mM) medium was studied using competitive antagonists. The effects of chloroethylclonidine (CEC) was investigated in Ca2+-free and normal Krebs' medium and RT-PCR was used to identify alpha1-adrenoceptor specific mRNA in epididymal vas deferens. In Ca2+-free medium, NA evoked sustained contractions but was less potent (pD2, 5.9) than in normal Krebs' medium (pD2, 7.3). The contractions in Ca2+-free medium were inhibited by prazosin (pA2, 9.3), 5-methylurapidil (pA2, 8.4), spiperone (pA2, 7.6) and BMY 7378 (pK(B), 6.8) consistent with activation of alpha1A-subtype. Repeated pretreatment with CEC (100 microM) reduced the potency of NA and maximum contractions in normal and Ca2+-free media. CEC-sensitivity in normal Krebs' medium was enhanced by prior treatment with phenoxybenzamine. mRNA for alpha1a- and alpha1d- but not alpha1b-adrenoceptors were detected in epididymal vas deferens. These results suggest that NA contracts the tissue in Ca2+-free medium by the stimulation of alpha1A-adrenoceptors. Two factors affecting CEC-sensitivity of NA-induced contractions in this tissue are discussed.

A comparison of the antagonistic activities of tamsulosin and terazosin against human vascular alpha1-adrenoceptors

Tamsulosin, a selective alpha1A-adrenoceptor antagonist, and terazosin, a non-selective one, are effective for the treatment of urinary disturbance due to benign prostatic hypertrophy. In the present study, their alpha1-adrenoceptor-blocking effects on blood vessels, which may cause orthostatic hypotension, were investigated in 10 healthy males. After the subjects took orally 0.2 mg of tamsulosin, 1 mg of terazosin or a lactate capsule as the control in a randomized cross-over fashion, their finger tip vasoconstrictor response to cold stimulation and vasoconstrictor response of the dorsal hand vein to increasing doses of phenylephrine were examined. The finger tip vasoconstrictor response was significantly reduced and the infusion rate of phenylephrine producing a half-maximal constriction was significantly increased by terazosin, but tamsulosin had no significant effect on these parameters. These data suggest that the usual dose of tamsulosin exerts little alpha1-adrenoceptor-blocking activity on blood vessels, and orthostatic episodes might be mild, if any, during the treatment with tamsulosin.

In vitro alpha1-adrenoceptor pharmacology of Ro 70-0004 and RS-100329, novel alpha1A-adrenoceptor selective antagonists

It has been hypothesized that in patients with benign prostatic hyperplasia, selective antagonism of the alpha1A-adrenoceptor-mediated contraction of lower urinary tract tissues may, via a selective relief of outlet obstruction, lead to an improvement in symptoms. The present study describes the alpha1-adrenoceptor (alpha1-AR) subtype selectivities of two novel alpha1-AR antagonists, Ro 70-0004 (aka RS-100975) and a structurally-related compound RS-100329, and compares them with those of prazosin and tamsulosin. Radioligand binding and second-messenger studies in intact CHO-K1 cells expressing human cloned alpha1A-, alpha1B- and alpha1D-AR showed nanomolar affinity and significant alpha1A-AR subtype selectivity for both Ro 70-0004 (pKi 8.9: 60 and 50 fold selectivity) and RS-100329 (pKi 9.6: 126 and 50 fold selectivity) over the alpha1B- and alpha1D-AR subtypes respectively. In contrast, prazosin and tamsulosin showed little subtype selectivity. Noradrenaline-induced contractions of human lower urinary tract (LUT) tissues or rabbit bladder neck were competitively antagonized by Ro 70-0004 (pA2 8.8 and 8.9), RS-100329 (pA2 9.2 and 9.2), tamsulosin (pA2 10.4 and 9.8) and prazosin (pA2 8.7 and 8.3 respectively). Affinity estimates for tamsulosin and prazosin in antagonizing alpha1-AR-mediated contractions of human renal artery (HRA) and rat aorta (RA) were similar to those observed in LUT tissues, whereas Ro 70-0004 and RS-100329 were approximately 100 fold less potent (pA2 values of 6.8/6.8 and 7.3/7.9 in HRA/RA respectively). The alpha1A-AR subtype selectivity of Ro 70-0004 and RS-100329, demonstrated in both cloned and native systems, should allow for an evaluation of the clinical utility of a 'uroselective' agent for the treatment of symptoms associated with benign prostatic hyperplasia.

Functional characterization of alpha1-adrenoceptor subtypes in longitudinal and circular muscle of human vas deferens

The alpha1-adrenoceptor subtype(s) mediating contraction to noradrenaline in longitudinal and circular muscle of human epididymal vas deferens was studied using competitive antagonists. The effects of the alkylating agents, phenoxybenzamine and chloroethylclonidine were also investigated. Noradrenaline evoked concentration-dependent contractions of longitudinal and circular muscle with comparable potencies (pD2; 5.6 and 5.5 respectively). The contractions in longitudinal and circular muscle respectively were inhibited by prazosin (pA2, 8.6 and pKB, 9.2), 5-methylurapidil (pKB, 8.7 and 9.1) and less potently by spiperone (pA2, 7.1) or BMY 7378 (pKB, 6.3 and 6.6). Contractions of the circular but not longitudinal muscle was comparatively insensitive to pretreatment with phenoxybenzamine. In contrast pretreatment with chloroethylclonidine reduced the contractions in both muscle types and also enhanced phenoxybenzamine-sensitivity in longitudinal but not circular muscle. The results suggest that contractions evoked by noradrenaline in both muscle types of human vas deferens is mediated via activation of alpha1-adrenoceptors with pharmacological profile of the alpha1A-subtype. However the involvement of alpha1A-adrenoceptor variants, such as the hypothesised alpha1L-subtype may underlie the differential effects of phenoxybenzamine in longitudinal and circular muscle. Factors contributing to chloroethylclonidine-sensitivity are discussed.

Influence of the alpha1-adrenergic antagonist, doxazosin, on noradrenaline-induced modulation of cytoskeletal proteins in cultured hyperplastic prostatic stromal cells

BACKGROUND

Doxazosin, an alpha1-adrenergic antagonist, inhibits sympathetic contraction of prostatic stromal smooth muscle cells and is used in the relief of obstructive benign prostatic hyperplasia (BPH). In vitro application of noradrenaline stimulates expression of cytoskeletal filaments, particularly actin and myosin, by prostatic stromal cells, thus enhancing their differentiation towards smooth muscle cells. This study examined the possible role of doxazosin in reversing this phenotypic modulation as well as in inhibiting smooth muscle cell contraction.

METHODS

Stromal cell tissue cultures derived from 10 human hyperplastic prostates were rendered quiescent by reduction of stripped fetal calf serum (FCS) to 1% (v/v) in the medium followed by treatment with 20 microM noradrenaline and/or 1 microM doxazosin for 10 days. Doxazosin, in 10-fold increments of concentration, was also added, separately, to two of these cell cultures, which were either quiescent or growing in 10% normal (unstripped) FCS. Harvested cells were labelled with fluorescein-labelled antisera to smooth muscle cytoskeletal filaments, and their individual fluorescence levels were analyzed flow-cytometrically.

RESULTS

Noradrenaline increased expression of all cytoskeletal filaments studied. This effect was greatest for actin and myosin in proliferating cell cultures. Doxazosin largely reversed the increase in filament expression. This effect was most significant for actin and myosin and greatest in quiescent cultures. However, inhibition of the agonist effect of noradrenaline by doxazosin showed no clear dose-related response, in that expression of cytoskeletal filaments was differentially inhibited.

CONCLUSIONS

The data suggest that doxazosin may inhibit not only stromal contraction of differentiated smooth muscle cells in BPH but also the phenotypic modulation of stromal smooth muscle cell differentiation induced by noradrenaline. These actions, together, may render prostatic stroma less contractile, and hence less able to respond to sympathetic stimulation, in patients with BPH. While effects on isolated stromal cells are of undoubted importance, failure to demonstrate a consistent dose-response relationship between expression of smooth muscle cell phenotype and inhibition by doxazosin suggests that additional influences, including humoral factors as well as the proximity of differentiated epithelium, are also likely to be involved in this interaction in the intact tissue.

Differential vascular alpha1-adrenoceptor antagonism by tamsulosin and terazosin

AIMS

In patients with lower urinary tract symptoms suggestive of benign prostatic obstruction the alpha1-adrenoceptor antagonist terazosin lowers blood pressure whereas only very small if any alterations were reported with the alpha1-adrenoceptor antagonist tamsulosin. Therefore, we have compared the vascular alpha1-adrenoceptor antagonism of tamsulosin and terazosin directly.

METHODS

Ten healthy subjects were investigated in a randomized, single-blind, three-way cross-over design and received a single dose of 0.4 mg tamsulosin, 5 mg terazosin or placebo on 3 study days at least 1 week apart. Before and 1, 3, 5, 7, 10 and 23.5 h after drug intake, alterations of diastolic blood pressure and other haemodynamic parameters in response to a graded infusion of the alpha1-adrenoceptor agonist phenylephrine were determined non-invasively.

RESULTS

At most time points tamsulosin inhibited phenylephrine-induced diastolic blood pressure elevations significantly less than terazosin (5 h time point: median difference in inhibition 35%, 95% CI: 18.7-50.3%). On the other hand, phenylephrine-induced changes of cardiac output, heart rate and stroke volume were similar during both active treatments.

CONCLUSIONS

In doses equi-effective for treatment of lower urinary tract symptoms tamsulosin causes less inhibition of vasoconstriction than terazosin.

Terazosin in benign prostatic hyperplasia: effects on blood pressure in normotensive and hypertensive men

OBJECTIVE

To determine the effects of terazosin on blood pressure and on antihypertensive therapy when used in managing benign prostatic hyperplasia (BPH).

PATIENTS AND METHODS

Safety data from a large, multinational study were analysed retrospectively. Normotensive and hypertensive patients received escalating dosages of terazosin for 10 weeks and were maintained on 5 or 10 mg daily doses for 16 weeks (single-blind period). After the initial treatment period, only men having sufficient improvements in International Prostate Symptom Score (> or = 30%) and in peak flow rate (> or = 10%) were randomly assigned to continue terazosin or to receive placebo for 24 weeks (double-blind period).

RESULTS

In hypertensive patients, terazosin reduced systolic blood pressure (SBP) and diastolic blood pressure (DBP) during the single-blind period; these clinically significant reductions were maintained in patients receiving terazosin during the double-blind period. However, in normotensive and controlled hypertensive patients terazosin produced no clinically significant mean changes in SBP or DBP during either study period. Terazosin did not adversely affect patients receiving concomitant antihypertensive medication.

CONCLUSION

Terazosin is a safe treatment for BPH in normotensive and hypertensive men, including men who are already taking additional antihypertensive drugs.

Quantification and distribution of alpha1-adrenoceptor subtype mRNAs in human proximal urethra

1. We performed RNase protection assays and in situ hybridization to investigate the ratio of the three alpha1-adrenoceptor subtype mRNAs, alpha1a, alpha1b and alpha1d, in human proximal urethra, and their localization in urethral cross-sections. As revealed by the RNase protection assays, alpha1a was the predominant subtype mRNA in both male and female urethral samples. Alpha1d mRNA was detected only in the female sample, and alpha1b mRNA was not detected in any of the samples tested. The ratio of the abundance of the subtype mRNAs, alpha1a:alpha1b:alpha1d, was 100:0:0 in the male urethra and 90:0:10 in the female urethra. 2. In situ hybridization studies showed no significant differences in the cross-sectional distribution of alpha1-adrenoceptor subtype mRNAs between male and female urethras. Intense alpha1a staining was observed in the smooth muscle of the urethra, but alpha1b and alpha1d staining was much less intense. 3. Of the three cloned alpha1 subtypes, alpha1a is the most likely to be responsible for the contraction of the human urethra. Owing to the side effects of nonselective alpha1 drugs, alpha1-selective drugs may be clinically superior to nonselective drugs for the treatment of urethral disorders.

Investigation of alpha1-adrenoceptor subtypes mediating vasoconstriction in rabbit cutaneous resistance arteries

1. Cutaneous resistance arteries (c.r.a.) (internal diameter=240.94+/-5.42 microm, n=67/25 (number arteries/number animals)) from New Zealand white rabbits were mounted in wire myographs and a normalization procedure followed. 2. Cumulative concentration-response curves (CCRCs) were constructed for the alpha-adrenoceptor agonists noradrenaline (NA), (R)A61603 and phenylephrine (PE) in the presence of cocaine (3 microM), propranolol (1 microM) and corticosterone (10 microM). The effects of competitive alpha1-adrenoceptor antagonists, prazosin, WB4101, 5-methyl-urapidil, HV723, BMY7378 and the irreversible alpha1B selective compound chloroethylclonidine (CEC) were examined versus the potency and maximum response of the c.r.a.s to noradrenaline. 3. The high potency of A-61603 relative to PE has been shown to differentiate both functional and binding site alpha1A- or alpha1B-adrenoceptors from alpha1D-adrenoceptors: A-61603 was 944 times more potent than phenylephrine (at EC50) suggesting the presence of a functional alpha1A or alpha1B as opposed to an alpha1D-subtype. 4. Exposure to chloroethylclonidine (CEC; 100 microM) decreased the maximum response to noradrenaline but did not significantly change noradrenaline sensitivity indicating that a substantial part of noradrenaline-induced vasoconstriction in rabbit cutaneous arteries is CEC-insensitive. 5. The potencies of prazosin (pA2=9.14) and WB4101 (pA2=9.30) indicate the involvement of prazosin-sensitive functional alpha1-adrenoceptors. The slopes of corresponding Schild plots for prazosin and WB4101 did not include negative unity which implies the possible involvement of more than one functional alpha1-adrenoceptor subtype in noradrenaline-induced vasoconstriction in rabbit cutaneous resistance arteries. In contrast to this, in the case of 5-methyl-urapidil and HV723, the Schild plot slope parameters were not significantly different from negative unity over the range of concentrations used; the low pA2 value for 5-methylurapidil (7.27) suggests the non-involvement of an alpha1A- or an alpha1D-adrenoceptor; the low pA2 value for HV723 (8.47) was similar to that against responses postulated as alpha1L. 6. We conclude that rabbit cutaneous resistance arteries express a prazosin-sensitive functional alpha1-adrenoceptor resembling the alpha1B and another low affinity site for prazosin which on the basis of the functional antagonism produced by HV723 most closely resembles the alpha1L-adrenoceptor; the low pA2 value for HV723 (8.47) is similar to that against responses postulated as alpha1L.

Characterization of subtype of alpha1-adrenoceptor mediating vasoconstriction in perfused rat hind limb

The subtype of alpha1-adrenoceptor mediating the exogenous noradrenaline-induced vasopressor response in perfused rat hind limb was determined by functional measurements and radioligand binding assays. The potencies (pA2 values) of alpha1A-adrenoceptor-selective antagonists, RS-17053 (N-[2-(2-cyclopropylmethoxy-phenoxy) ethyl]-5-chloro-alpha,alpha-dimethyl-1H-indole-3-ethanamine hydrochloride), WB 4101 (2-(2,6-dimethoxyphenoxyethyl) aminomethyl-1,4 benzodioxane), 5-methyl-urapidil, and the alpha1D-adrenoceptor-selective antagonist, BMY 7378 (8-[2-[4-(2-methoxyphenyl)-1-piperazinyl]ethyl]-8-azaspirol[4.5]de cane-7,9-dione), to inhibit the noradrenaline-induced vasopressor response determined by Schild plot were 9.47 +/- 0.21, 9.48 +/- 0.19, 8.10 +/- 0.27 and 6.66 +/- 0.14, respectively, with no slope significantly different from unity. The affinities (K(i) values) of these antagonists were determined by displacement of 125I-BE 2254 (2-beta(4-hydroxyphenyl)-ethylaminomethyl)-tetralone) binding from the cloned alpha1a-, alpha1b-, alpha1d-adrenoceptor, stably expressed in human embryonic kidney (HEK) 293 cells. The pA2 values of the above antagonists correlated well with the binding K(i) values only for alphaIA-adrenoceptors (r = 0.93), but not for alpha1B-adrenoceptors (r = 0.51) and alpha1D-adrenoceptors (r = 0.13). The concentration-vasopressor response curve for noradrenaline was not significantly affected by pretreatment with 50 microM chloroethylclonidine for 30 min. The results suggest that only alpha1A-adrenoceptors mediate the noradrenaline-induced vasopressor response in perfused rat hind limb.

The effects of tamsulosin, a high affinity antagonist at functional alpha 1A- and alpha 1D-adrenoceptor subtypes

1. The actions of the alpha 1-adrenoceptor antagonist tamsulosin have been examined at functional alpha 1-adrenoceptor subtypes and compared with those at the human prostate receptor. 2. At the alpha 1D-adrenoceptors of the rat aorta, tamsulosin acted as a competitive antagonist with a high affinity (pKB = 10.1). 3. At the alpha 1B-adrenoceptor of the rat spleen and rabbit corpus cavernosum penis, tamsulosin again acted as a competitive antagonist but with a significantly lower affinity (pKB = 8.9-9.2). 4. Tamsulosin acted as an unsurmountable antagonist of the alpha 1A-adrenoceptor-mediated responses of the rat and human vas deferens, reducing maximal responses to phenylephrine by 20% and 50%, respectively, at an antagonist concentration of 1 nM. Responses of depolarized (100 mM KCl) rat vas deferens preparations were unaffected by 10 nM tamsulosin but this concentration reduced maximal responses to 5-hydroxytryptamine (5-HT) in this tissue. 5. When longer antagonist incubation periods (> or = 60 min) were used, tamsulosin behaved as a competitive antagonist on the human prostate with a significantly higher affinity (pKB = 10.0) than obtained at the alpha 1B-adrenoceptor. 6. The data demonstrate that tamsulosin is a high affinity antagonist at functional alpha 1-adrenoceptors with a selectivity alpha 1D > or = alpha 1A > alpha 1B. In some tissues the compound exhibits an additional unsurmountable antagonist action, the clinical significance of which is unknown.

NS-49, an alpha 1A-adrenoceptor agonist, selectively increases intraurethral pressure in dogs

The effects of NS-49 ((R)-(-)-3'-(2-amino-1-hydroxyethyl)-4'-fluoromethane sulfonanilide hydrochloride), an alpha 1A-adrenoceptor-selective agonist, on intraurethral pressure and blood pressure were investigated in anesthetized dogs. In addition, the contractile effects of NS-49 on the isolated dog urethra and carotid artery were compared with those of non-selective alpha 1-adrenoceptor agonists. Intravenously (i.v.) administered NS-49 at 0.3 microgram/kg or more significantly increased intraurethral pressure in a dose-dependent manner. Much higher doses of NS-49 were needed to increase blood pressure. In contrast, ST-1059 (1-(2',5'-dimethoxyphenyl)-2-aminoethanol) (an active metabolite of midodrine) at 30 micrograms/kg or more significantly increased both intraurethral pressure and blood pressure. NS-49 was 11-fold more selective for intraurethral pressure than ST-1059, NS-49, ST-1059, phenylephrine and noradrenaline caused concentration-dependent contraction of the isolated dog urethra. NS-49 caused only a slight contraction of the dog carotid artery even at high concentrations, whereas the reference drugs caused contractions of the artery with high efficacy. The alpha 1A-adrenoceptor-selective antagonists 5-methyl-urapidil and WB-4101 also showed high affinity for alpha 1-adrenoceptors in the dog urethra in inhibiting [3H]prazosin binding. In conclusion, the alpha 1A-selective agonist NS-49 selectively increased intraurethral pressure in dogs, and produced selective contraction of the dog urethra. These results suggest that the alpha 1A-adrenoceptor subtype is responsible for the contraction of the urethra and the regulation of intraurethral pressure, and that NS-49 might be useful for the treatment of stress incontinence with little effect on the cardiovascular system.

Effect of KMD-3213, an alpha 1a-adrenoceptor-selective antagonist, on the contractions of rabbit prostate and rabbit and rat aorta

KMD-3213, (-)-(R)-1-(3-hydroxypropyl)-5-[2-[[2-[2-(2,2,2-trifluoroethoxy) phenoxy]ethyl]amino]propyl]indoline-7-carboxamide, a newly synthesized alpha 1-adrenoceptor antagonist, has been shown to have potent action toward, and to be selective for human cloned and native alpha 1-adrenoceptors. In the present study, we characterized the inhibitory effect of KMD-3213 on the phenylephrine (alpha 1-adrenoceptor-selective agonist)-induced contraction of rabbit prostate, rabbit thoracic aorta and rat thoracic aorta to functionally confirm the tissue selectivity of KMD-3213. The mean pA2 value for KMD-3213 for the inhibition of the rabbit prostatic contraction was 10.05, whereas the values for the rabbit and rat aortic contractions were 9.36 and 8.13, respectively. The order of mean pA2 values for the inhibition of the rabbit prostatic contraction was KMD-3213 > or = tamsulosin >> prazosin, whereas that for the rabbit and rat aortic contractions was tamsulosin > KMD-3213 > prazosin and tamsulosin > or = prazosin >> KMD-3213, respectively. KMD-3213 produced a sigmoidal inhibition curve for single-dose phenylephrine-induced contractions of rabbit prostate, whereas it produced a non-sigmoidal curve for that of rabbit aorta. KMD-3213 had no effect on isoproterenol-induced chronotropic action in guinea-pig atria, and 5-hydroxytryptamine-, histamine- and acetylcholine-mediated contractions of rabbit aorta. These results indicate that the potency of the inhibitory activity of KMD-3213 depends on the tissue subtype expression and that KMD-3213 preferentially antagonizes prostatic contraction.

The effects of SB 216469, an antagonist which discriminates between the alpha 1A-adrenoceptor and the human prostatic alpha 1-adrenoceptor

1. The affinity of the alpha 1-adrenoceptor antagonist SB 216469 (also known as REC 15/2739) has been determined at native and cloned alpha 1-adrenoceptor subtypes by radioligand binding and at functional alpha 1-adrenoceptor subtypes in isolated tissues. 2. In radioligand binding studies with [3H]-prazosin, SB 216469 had a high affinity at the alpha 1A-adrenoceptors of the rat cerebral cortex and kidney (9.5-9.8) but a lower affinity at the alpha 1B-adrenoceptors of the rat spleen and liver (7.7-8.2). 3. At cloned rat alpha 1-adrenoceptor subtypes transiently expressed in COS-1 cells and also at cloned human alpha 1-adrenoceptor subtypes stably transfected in Rat-1 cells, SB 216469 exhibited a high affinity at the alpha 1a-adrenoceptors (9.6-10.4) with a significantly lower affinity at the alpha 1b-adrenoceptor (8.0-8.4) and an intermediate affinity at the alpha 1d-adrenoceptor (8.7-9.2). 4. At functional alpha 1-adrenoceptors, SB 216469 had a similar pharmacological profile, with a high affinity at the alpha 1A-adrenoceptors of the rat vas deferens and anococcygeus muscle (pA2 = 9.5-10.0), a low affinity at the alpha 1B-adrenoceptors of the rat spleen (6.7) and guinea-pig aorta (8.0), and an intermediate affinity at the alpha 1D-adrenoceptors of the rat aorta (8.8). 5. Several recent studies have concluded that the alpha 1-adrenoceptor present in the human prostate has the pharmacological characteristics of the alpha 1A-adrenoceptor subtype. However, the affinity of SB 216469 at human prostatic alpha 1-adrenoceptors (pA2 = 8.1) determined in isolated tissue strips, was significantly lower than the values obtained at either the cloned alpha 1a-adrenoceptors (human, rat, bovine) or the native alpha 1A-adrenoceptors in radioligand binding and functional studies in the rat. 6. Our results with SB 216469, therefore, suggest that the alpha 1-adrenoceptor mediating contractile responses of the human prostate has properties which distinguish it from the cloned alpha 1a-adrenoceptor or native alpha 1A-adrenoceptor. Since it has previously been shown that the receptor is not the alpha 1B- or alpha 1D-adrenoceptor, the functional alpha 1-adrenoceptor of the human prostate may represent a novel receptor with properties which differ from any of the alpha 1-adrenoceptors currently defined by pharmacological means.

The alpha-adrenoceptor antagonist properties of the enantiomers of doxazosin in the human prostate

The alpha-adrenoceptor antagonist properties of doxazosin and its enantiomers were characterized using human prostate tissue and cell membranes isolated from rat-1 fibroblast expressing each of the cloned human alpha 1-adrenoceptor subtypes. In the alpha 1-adrenoceptor-binding studies on the human prostate with [3H]doxazosin and 2-{[beta-(3-[125I],4-hydroxyphenyl)ethyl]aminomethyl}-l-tetralone ([125I]HEAT), no significant differences were observed between racemic doxazosin, R-doxazosin and S-doxazosin (mean -log Ki (pKi) values were 8.60-8.63, 8.47-8.55 and 8.61-8.65, respectively), whereas the alpha 2-adrenoceptor-binding studies with [3H]rauwolscine and [3H]clonidine revealed that the alpha 2-adrenoceptor-binding affinity of S-doxazosin (pKi = 5.91-5.94) was slightly (3- or 4-fold), but significantly lower than that of R-doxazosin (pKi = 6.47-6.54). Studies in phenylephrine-contracted prostatic tissue showed no significant difference in alpha 1-adrenoceptor antagonist potency between racemic doxazosin, R-doxazosin and S-doxazosin (pA2 values were 8.43 +/- 0.28, 8.64 +/- 0.56 and 8.75 +/- 0.38, respectively). In the binding studies with cloned alpha 1-adrenoceptor subtypes using [3H]prazosin and [125I]HEAT, racemic doxazosin, R-doxazosin and S-doxazosin showed no selectivity for the alpha 1-adrenoceptor subtypes. The present study demonstrated that doxazosin and its enantiomers are highly selective alpha 1-adrenoceptor antagonists and that there is no evidence suggesting differential alpha 1-adrenoceptor antagonist effects of doxazosin and its enantiomers in the human prostate. Doxazosin, therefore, could be described as displaying balanced activity across all three alpha 1-adrenoceptor subtypes.

Different subtypes of alpha 1A-adrenoceptor mediating contraction of rat epididymal vas deferens, rat hepatic portal vein and human prostate distinguished by the antagonist RS 17053

1. The alpha 1-adrenoceptor subtype mediating contraction of the rat hepatic portal vein to phenylephrine was characterized by use of competitive antagonists previously shown to have selectivity between the expressed alpha 1-subtype clones. Prazosin competitively antagonized the phenylephrine contractions with a pA2 value of 9.2, as did WB 4101 (pA2 9.4), 5-methyl urapidil (pA2 8.6), indoramin (pA2 8.4) and BMY 7378 (pA2 6.5). 2. The pA2 values on the rat portal vein correlated highly with their previously published pA2 values for the alpha 1A-adrenoceptors mediating contraction of the rat epididymal vas deferens and human prostate and poorly with those for the alpha 1B- and alpha 1D-adrenoceptors mediating contraction of the rat spleen and aorta, respectively. The antagonist pA2 values on the rat portal vein correlated highly with their previously published pK1 values for the expressed alpha 1a-clone and poorly with those for the expressed alpha 1b- and alpha 1d-clones. Therefore the results show that contraction of the rat portal vein to phenylephrine is mediated by alpha 1A-adrenoceptors. 3. The novel alpha 1-adrenoceptor antagonist RS 17053 had a relatively high affinity for the alpha 1A-adrenoceptors mediating contraction of the rat epididymal vas deferens (pA2 9.5) compared with the alpha 1B-adrenoceptors in the rat spleen (pA2 7.2) or the alpha 1D-adrenoceptors in the rat aorta (pKB 7.1), in agreement with its selectivity for the expressed alpha 1a-clone. However, RS 17053 had over 100 fold lower affinity for the alpha 1A-adrenoceptors mediating contraction of the rat portal vein (pKB 7.1) and human prostate (pKB 7.1) compared with its affinity for the alpha 1A-adrenoceptors in the rat epididymal vas deferens or the expressed alpha 1a-clone. 4. The difference in affinity of RS 17053 between the rat epididymal vas deferens and rat portal vein cannot be explained by a species difference in the receptor. Therefore RS 17053 may distinguish between subtypes of the alpha 1A-adrenoceptor in the rat portal vein and human prostate compared with those in the rat epididymal vas deferens or the expressed alpha 1a-clone.

Pharmacological characterization of alpha 1-adrenoceptor subtype mediating regulation of arterial pressure and urethral perfusion pressure in the anaesthetized rat

1. The alpha 1-adrenoceptor subtypes mediating the regulation of arterial pressure (AP) and urethral perfusion pressure (UP) in the anaesthetized rat were characterized by using selective alpha 1-adrenoceptor agonists and antagonists. 2. Intravenous administration of selective alpha 1-adrenoceptor agonists elicited a dose-dependent increase in AP and UP. The rank order of agonist potency: oxymetazoline (ED50, 6.2 and 8.2 nmol kg-1 > phenylephrine (ED50, 32 and 27 nmol kg-1 > methoxamine (ED50, 300 and 296 nmol kg-1 was the same for AP and UP, respectively. 3. The effects of phenylephrine on AP and UP were antagonized, in a dose related-manner, by pretreatment with alfuzosin, BMY 7378, 5-methyl-urapidil, phentolamine, prazosin, spiperone and WB 4101.5-methyl-urapidil was the only alpha 1-adrenoceptor antagonist more potent on UP than on AP. 4. The potency of the different alpha 1-adrenoceptor antagonists tested on AP and UP was significantly correlated with their binding affinity for the expressed recombinant alpha 1a-, but not alpha 1b- or alpha 1d-, adrenoceptor subtype. 5. The results suggest that in the anaesthetized rat (1) both AP and UP are regulated by the alpha 1A-adrenoceptor subtype; and (2) the urogenital selectivity of 5-methyl-urapidil may be due to the existence of multiple forms of the alpha 1A-adrenoceptor.

Tamsulosin, a selective alpha 1c-adrenoceptor antagonist: a randomized, controlled trial in patients with benign prostatic 'obstruction' (symptomatic BPH). The European Tamsulosin Study Group

OBJECTIVE

To evaluate the efficacy and safety of tamsulosin 0.4 mg once daily (as a modified-release formulation) compared with placebo in patients with benign prostatic enlargement, lower urinary tract symptoms and prostatic 'obstruction' (symptomatic benign prostatic hyperplasia [BPH]).

PATIENTS AND METHODS

Of 313 patients with symptomatic BPH enrolled in a 2-week placebo run-in period, 296 were subsequently randomized to receive either placebo (98 patients) or tamsulosin 0.4 mg once daily (198 patients) for 12 weeks. The primary variables assessed to determine efficacy were maximum urinary flow rate (Qmax) from free-flow measurements and the total Boyarsky symptom score.

RESULTS

Tamsulosin produced greater improvements in Qmax (1.4 mL/s, 13.1%) than did placebo (0.4 mL/s, 3.8%) (P = 0.028) and a greater decrease in total symptom score (3.4 points, 35.8% reduction) than did placebo (2.2 points, 23.7% reduction) (P = 0.002). Significantly more tamsulosin-treated patients (67%) than placebo-treated patients (44%) had a > or = 25% decrease in total symptom score after 12 weeks (P < 0.001). Treatment with tamsulosin for 12 weeks also produced significant improvements in average urinary flow rate (P = 0.040), irritative (P = 0.013) and obstructive (P = 0.014) symptom scores and symptoms of nocturia (P = 0.022) and hesitancy (P = 0.004). Tamsulosin was tolerated well by the patients. The incidence of adverse events emerging during treatment was comparable in the tamsulosin- and placebo-treated groups (34% and 24% respectively, P = 0.109), as was the incidence of cardiovascular-related adverse events (5% and 7% respectively; P = 0.596). There were no significant differences in changes in blood pressure or pulse rates between the tamsulosin- and placebo-treated groups.

CONCLUSION

Tamsulosin 0.4 mg once daily is safe, well tolerated and clinically effective in improving symptoms and urinary flow rate in patients with symptomatic BPH.