Effects of prazosin in patients with benign prostatic obstruction

A prospective pilotstudy comparing the anesthetic effects of an alpha-2 agonist during holmium laser resection of the prostate and transurethral resection for prostate surgery for benign prostatic hyperplasia patients using selective alpha-1 blockers

BACKGROUND

To examine the response to an α2receptor agonist used as a sedative for patients using long-term selective α1 blockers.

METHODS

Sixty-nine consecutive patients undergoing transurethral prostate resection or holmium laser resection of the prostateunder spinal anesthesia were divided into two groups; group N (n = 37), which did not receive α1 blockers, and group T (n = 32), which was administered tamsulosin for at least 1 month before the study. Bispectral index scores, Modified Observer's Assessment of Alertness/Sedation scale scores, heart rate, and mean blood pressure were obtained under sedation using dexmedetomidine for 30 min during surgery.

RESULTS

The only significant difference found between the groups were mean bloodpressure 15 min after the first loading dose injection of dexmedetomidine. Differencesbetween both groupswere noted at 15 min(group T: 100.2 ± 12.9 mmHg; group N: 90.0 ± 17.5 mmHg; P = 0.08), 20 min (group T: 99.8 ± 12.3 mmHg; group N: 87.4 ± 15.0 mmHg; P < 0.00), 25 min (group T: 99.3 ± 13.4 mmHg; group N: 85.4 ± 13.8 mmHg; P < 0.00), and 30 min (group T: 98.8 ± 13.1 mmHg; group N: 84.5 ± 13.5 mmHg; P < 0.00).

CONCLUSIONS

The use of α2 agonists is appropriate during surgery for benign prostatic hyperplasia patients using tamsulosin, and there is no need to alter the dose. Alertness with anesthesia involving α2 agents was maintained for patients using long-term tamsulosin and patients who did not use tamsulosin.

TRIAL REGISTRATION

The study was retrospectively registered with the Clinical Research Informational Service ( KCT0002967 , July 2, 2018).

Is Tamsulosin Linked to Dementia in the Elderly?

PURPOSE OF REVIEW

Lower urinary tract symptoms (LUTS) result from age-related changes in detrusor function and prostatic growth that are driven by alterations in the ratio of circulating androgens and estrogens. Alpha-adrenergic receptor blockers are commonly used to treat LUTS because they influence urethral tone and intra-urethral pressure. Molecular cloning studies have identified three α₁-adrenergic receptor subtypes (α_1A, α_1B, and α_1D). The α_1A subtype is predominant in the human prostate but is also present in many parts of the brain that direct cognitive function. Tamsulosin is the most widely used α₁-adrenergic receptor antagonist with 12.6 million prescriptions filled in 2010 alone. When compared to the other common types of α₁-adrenergic receptor antagonists (i.e., terazosin, doxazosin, and alfuzosin), tamsulosin is 10- to 38-fold more selective for the α_1A versus the α_1B subtype.

RECENT FINDINGS

Duan et al. have recently shown that men taking tamsulosin have a higher risk of developing dementia when compared to men taking other α-adrenergic antagonists or no α-adrenergic antagonists at all (HR 1.17; 95% CI 1.14-1.21). Based upon this retrospective analysis, we believe that tamsulosin, because of its unique affinity for α_1A-adrenergic receptors, may increase the risk of developing dementia when used for an extended period of time. If these findings are confirmed, they carry significant public health implications for an aging society.

[S2e guideline of the German urologists: Conservative and pharmacologic treatment of benign prostatic hyperplasia]

This report summarizes the relevant aspects of the S2e guideline of the German Urologists for the conservative and pharmacological treatment of lower urinary tract symptoms due to benign prostatic hyperplasia. Recommendations are given regarding watchful waiting, behavioral therapy, phytotherapy and pharmacological mono- and combination therapy. The influence of the different therapeutic options on bladder outlet obstruction (BOO) is described in detail.

Outcomes and quality of life issues in the pharmacological management of benign prostatic hyperplasia (BPH)

BACKGROUND

Benign prostatic hyperplasia (BPH) is a common disease of the aging male population. BPH treatment includes a variety of pharmacological and surgical interventions. The goal of this paper is to review the natural history of BPH, outcomes of pharmacological management, effects on quality of life (QoL), future pharmacotherapies, and associated patient-focused perspectives.

MATERIALS AND METHODS

Medline searches for the keywords benign prostatic hyperplasia, BPH, alpha blockers, 5 alpha-reductase, and quality of life were performed. Relevant literature was reviewed and analyzed.

RESULTS

Alpha blockers, 5 alpha-reductase inhibitors, and phytotherapy are the three categories of pharmaceutical interventions currently available for BPH. Various clinical trials have shown that alpha blockers and 5 alpha-reductase inhibitors are safe, efficacious, and improve QoL in patients with BPH. The evidence for phytotherapeutics is not as convincing. The current armamentarium of pharmaceutical interventions are encompassed in these three classes of medications. New pharmacotherapies based on novel mechanisms are on the horizon.

CONCLUSION

There are a variety of safe and efficacious medical therapies available for the management of BPH and it is important for the practicing physician to have an understanding of these pharmacotherapies and their potential impact on the patient. There is not enough evidence to make a recommendation regarding phytotherapy use. New classes of drugs for BPH will likely find their way into routine use.

α1-Adrenoceptor Subtypes in Bovine Prostate

The object of this study was to examine the existence and characteristics of α1-adrenoceptor subtypes in the bovine prostate using the radioligand binding assay method. [3H]Prazosin was used as the radioligand and its binding sites in bovine prostate were classified into two subtypes. One subtype showed a high affinity (α1High, Kd: 101·1 Pm and Bmax: 11·8 fmol (mg protein)−1) and the other had a low affinity (α1Low, Kd: 3371·4 Pm and Bmax: 50·5 fmol (mg protein)−1). Although the same pKi values of clorethylclonidine, p-aminoclonidine, benoxathian and dibenamine to both α1High and α1  Low binding sites in bovine prostate tissue were observed, other α1 antagonists used in this study had different pKi values for the two α1-adrenoceptor subtypes. The existence and binding characteristics of α1-adrenoceptor subtypes in bovine prostate were clarified. It is possible that agents selective for one site may contribute to the development of better drugs for the treatment of bladder outlet obstructions of men with benign prostatic hyperplasia.

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.

Urinary incontinence: classification and pharmacological therapy

Pharmacological therapy has been developed which can have significant impact in the management of many forms of urinary incontinence and voiding dysfunction. In general the clinical laboratory studies which have supported or challenged the efficacy of many of the commonly prescribed drugs for voiding dysfunction are often difficult to interpret and contradictory. The available clinical studies often do not demonstrate a lack of bias. Nor do they include an adequate number of subjects, use appropriate and sensitive methods of evaluation, employ double-blind placebo-controlled design, or appear statistically valid. Although the contribution of laboratory research has been of unquestionable value in the development of our current knowledge of lower urinary tract pharmacology it is difficult to interpret the results of in vitro pharmacological studies because of the array of experimental models used and the need to extrapolate to in vivo activity. This paper utilizes a functional scheme which classifies agents by their effects on urinary storage and emptying. The purpose of this review is to promote discussion of the application of uropharmacological investigation to the development of newer, more efficacious forms of drug therapy.

Management of Benign Prostate Hyperplasia: An Overview of α-Adrenergic Antagonist

Benign prostate hyperplasia (BPH) is common among above 50 years age group, interfere with normal activities of lower urinary tract function and reduce the sense of well being. It can also be progressive, with a lost of urinary retention, bladder infection, bladder calculus and renal failure. Although many men with mild to moderate symptoms to well without therapy, others have gradually increasing symptoms and require medical therapy or surgery. BPH is the non-malignant, uncontrolled growth of cells in the prostate gland. This cell growth usually occurs in the tissue that surrounds the urethra as it passes through the prostate gland to the bladder. As BPH progresses, the gland constricts the urethra and obstructs the urine outflow. The bladder no longer empties completely, creating an environment in which infections, bladder stones, and chronic prostatities may develop. If left untreated, chronic obstruction can lead to the back up of urine into the ureters and compromise kidney function. In hyperplastic prostate tissue, the prostate capsule, and the bladder neck are blocked, by using alpha-adrenergic antagonist drugs; the smooth muscle tone of these structures is decreased. As a result, resistance to urinary flow through the bladder neck and the prostatic urethra decreases and urinary flow increases. A variety of alpha-adrenergic antagonists with distinct properties have been investigated as possible treatments for benign prostate hyperplasia.

alpha1-Adrenoceptor subtype selectivity and lower urinary tract symptoms

Benign prostatic hyperplasia is a common cause of urinary flow obstruction in aging men and may lead to lower urinary tract symptoms (LUTS). Benign prostatic hyperplasia has 2 physiological components: a static component related to increased prostate size and a dynamic component related to increased prostate smooth muscle tone. alpha1-Adrenoceptors (alpha1ARs) maintain prostate smooth muscle tone; hence, alpha1-antagonists (blockers) relax prostate smooth muscle and decrease urethral resistance, ultimately leading to relief of LUTS. This review focuses on alpha1AR subtypes and their location in lower urinary tract tissues involved in LUTS (prostate, bladder, spinal cord); it also summarizes major clinical trials published to date on the efficacy of alpha1AR blockers for LUTS. Benefits and adverse effects of clinically available alpha1AR antagonists are reviewed, followed by recent information on interactions between alpha1AR subtype antagonists and type 5 phosphodiesterase inhibitors used for impotence. alpha1-Adrenoceptor antagonists have become the mainstay of therapy for LUTS; knowledge about specific alpha1AR subtypes should facilitate rational choice of alpha1AR blocker therapy by clinicians.

Changing aspects in the evaluation and treatment of patients with benign prostatic hyperplasia

Lower urinary tract symptoms are a common clinical symptom among men and a frequent reason for referring to a urologist. The most important information comes from the patient history because evaluation of symptoms is fundamental in the diagnosis and treatment planning for LUTS. Other aspects of the initial evaluation, such as the physical examination and initial laboratory values, can provide valuable additional information about the severity of the disease and the need for treatment. If treatment is warranted based on this information, additional diagnostic tests may be appropriate to set a pretreatment baseline, rule out other conditions, and plan treatment approach. Fortunately, a variety of effective medical and surgical treatments are available to treat this common disease.

Modulation of phenotype of human prostatic stromal cells by transforming growth factor-betas

BACKGROUND

We investigated the effects of transforming growth factor (TGF)-betas on morphological and receptor phenotypes, as well as proliferation of four currently established human prostatic myofibroblast cell lines and one commercially available prostatic stromal cell line.

METHODS

The effects of TGF-betas on morphological changes and proliferation of the cells were studied by immunohistochemistry and bromodeoxyuridine assay, respectively. The expression of alpha 1-receptor subtypes was measured by real time quantitative reverse transcription-polymerase chain reaction (RT-PCR) and the radioligand binding assay for the receptors was also performed.

RESULTS

TGF-betas 1, 2, and 3 induced expression of desmin and myosin of cells of the established cell lines, and significantly inhibited their growth. The alpha 1a-receptor was expressed only in the commercially available cell line and alpha 1b and 1d, in all cell lines. TGF-beta 1 suppressed the expression of all three subtypes of the alpha 1-receptor. The binding sites of cells of all the cell lines were reduced by treatment with this growth factor.

CONCLUSIONS

TGF-betas may induce human prostatic stromal cells to express the smooth muscle phenotype and inhibited their growth. However, the growth factor reduced the binding sites of the receptor and suppressed mRNA expression of its subtypes, suggesting that morphological and receptor phenotypes may be regulated via more than one pathway by TGF-beta(s).

Postvoid residual urine in patients with lower urinary tract symptoms suggestive of benign prostatic hyperplasia: pooled analysis of eleven controlled studies with alfuzosin

OBJECTIVES

A pooled analysis was conducted in patients with lower urinary tract symptoms suggestive of benign prostatic hyperplasia to examine the relationship between the postvoid residual urine (PVR) volume and various clinical characteristics and to assess the effect of alfuzosin, a clinically uroselective alpha(1)-blocker, on PVR volume and any other associated outcome.

METHODS

Nine hundred fifty-three patients, 42 to 89 years old, with a baseline PVR volume between 50 and 350 mL (mean 106 mL) were enrolled in 11 double-blind controlled studies and received either alfuzosin (n = 607) or placebo (n = 346) for 1 to 6 months. The relationships between the baseline PVR volume measured by transabdominal ultrasound and age, symptoms, maximum flow rate (Qmax), estimated bladder capacity, and prostate-specific antigen level were assessed. The changes in the PVR volume with treatment were evaluated in all available patients at three endpoints (1, 3, and 6 months).

RESULTS

At baseline, a PVR volume of 100 mL or greater was observed in 60%, 47%, and 39% of patients with a Qmax less than 8, 8 to 11, and greater than 11 mL/s, respectively (P = 0.001). The bladder capacity was also significantly related to the Qmax (P = 0.0001). No relationship was found between PVR volume and age, symptoms, or prostate-specific antigen level. The changes in the PVR volume with treatment were related to the baseline PVR volume. However, at all endpoints and whatever the baseline PVR volume, the decreases in the PVR volume were significantly (P <0.01) greater with alfuzosin than with placebo. Acute urinary retention occurred in 7 patients (2 [0.3%] of 607 patients taking alfuzosin and 5 [1.4%] of 346 patients taking placebo); 6 of these 7 patients had a baseline PVR volume greater than 100 mL.

CONCLUSIONS

In this population of men with lower urinary tract symptoms suggestive of benign prostatic hyperplasia, the PVR olume and bladder capacity were related to the baseline Qmax. Alfuzosin significantly reduced the PVR volume compared with placebo, and this effect was more marked in patients with a high PVR volume at baseline. Acute urinary retention occurred mainly in patients with a PVR volume greater than 100 mL and was less frequent in patients taking alfuzosin than in those taking placebo.

Comparison of prazosin, terazosin and tamsulosin in the treatment of symptomatic benign prostatic hyperplasia: a short-term open, randomized multicenter study. BPH Medical Therapy Study Group. Benign prostatic hyperplasia

BACKGROUND

The objective of this open randomized clinical study was to compare the short-term efficacy and safety of three alpha-1 blockers, prazosin, terazosin and tamsulosin, in the treatment of lower urinary tract symptoms (LUTS) associated with benign prostatic hyperplasia (BPH).

METHODS

The study comprised 121 patients with symptomatic BPH who were randomized to receive 0.5 mg of prazosin twice daily, 0.5 mg of terazosin twice daily or 0.1 mg of tamsulosin once daily for the initial 2 weeks. The doses were doubled for the next 2 weeks. The primary variables assessed were a symptom score, changes in maximum and average urinary flow rate (Qmax and Qave), postvoid residual urine volume and blood pressure.

RESULTS

The percentage changes in the total symptom score from baseline were 38, 39 and 26% at 4 weeks by prazosin, terazosin and tamsulosin, respectively. Terazosin produced significantly higher improvement in four out of nine individual symptoms than tamsulosin (P < 0.05). A significant increase in Qmax or Qave in uroflowmetry was obtained in the prazosin and tamsulosin groups. Blood pressure remained unchanged in normotensive patients, but significantly decreased in hypertensive patients except for the tamsulosin group. Adverse events were minimal in all treatment groups.

CONCLUSIONS

The efficacy and safety profiles were different among the alpha-1 blockers at standard doses. Tamsulosin appears to be safer than the others for aged patients or patients with hypertension who have impaired blood pressure regulation, while terazosin is significantly effective in improving symptomatic score when compared with the others examined. It is recommended that the alpha-1 blocking agent and its optimal dose are selected on the basis of the baseline characteristics of the patients with symptomatic BPH.

Effect of JTH-601, a novel alpha(1)-adrenoceptor antagonist, on prostate function in dogs

We examined the effect of JTH-601 (3-¿N-[2-(4-hydroxy-2-isopropyl-5-methylphenoxy)ethyl]-N-methylaminom ethyl¿-4-methoxy-2,5,6-trimethylphenol hemifumarate), a new alpha(1L)-adrenoceptor antagonist, on prostatic function in isolated canine prostate and in anesthetized dogs. In the contraction study, phenylephrine and noradrenaline produced concentration-dependent contractions in canine prostate and carotid artery, respectively. In these tissues, JTH-601, prazosin (a non-selective alpha(1)-adrenoceptor antagonist), and tamsulosin (an alpha(1A)-adrenoceptor antagonist) competitively antagonized contraction in a concentration-dependent manner. The pA(2) (pK(B)) values with prostate were 8.49+/-0.07 for JTH-601, 7.94+/-0.04 for prazosin and 9.42+/-0.22 for tamsulosin. The ratio of pA(2) (carotid artery/prostate), i.e. prostatic selectivity, was 10.471 for JTH-601, 0.008 for prazosin and 0.371 for tamsulosin, respectively. In anesthetized dogs, JTH-601 (1 mg/kg, i.d.) significantly decreased urethral pressure by 15% without affecting blood pressure or heart rate. Tamsulosin (0.1 mg/kg, i.d.) decreased urethral pressure to the same extent as did JTH-601, but with a significant effect on blood pressure and heart rate. JTH-601 showed higher selectivity for canine prostate both in vitro and in vivo. In prostate, an important role of the alpha(1L)-adrenoceptor is suggested in the smooth muscle contraction mediated by alpha(1)-adrenoceptors. JTH-601 is expected to be an effective alpha(1)-adrenoceptor antagonist for the treatment of urinary outlet obstruction by benign prostatic hypertrophy with a minimum effect on the cardiovascular system.

Effects of doxazosin in men with benign prostatic hyperplasia: urodynamic assessment

OBJECTIVE

In this study, a randomized and placebo controlled trial, we aimed to study the effectiveness and safety of doxazosin based upon urodynamic parameters, especially pressure/flow studies, in men with benign prostatic hyperplasia (BPH).

MATERIALS AND METHODS

A total of 57 men (29 doxazosin, 28 placebo) 48-82 years of age with BPH were enrolled. Yet, 8 of 29 in the doxazosin group and 10 of 28 in the placebo group were excluded due to side effects of doxazosin and intolerability of urodynamic assessment of free uroflow, postvoiding residual urine volume (PVR) and pressure/flow studies.

RESULTS

There were improvements in all urodynamic parameters (Free Qmax: 30.4% and 28%, PVR: 14 ml and 12 ml, invasive Qmax: 29.3% and 26.2%, Pdet at Qmax: -32.7% and -30%, Pdet-max: -29% and -27.7% at end of the 1st and 6th months whereas placebo effects were worsening in all urodynamic parameters.

CONCLUSIONS

We suggest that doxazosin is an important treatment option for patients with BPH, and efficacy of doxazosin should be evaluated with objective, quantitative urodynamic studies not with subjective symptom scores. But additional costs and invasiveness of urodynamic studies restrict their common usefulness.

Subtype selective alpha1-adrenoceptor antagonists for the treatment of benign prostatic hyperplasia

Benign prostatic hyperplasia (BPH) is highly prevalent in the male population beyond the age of 60. Impairment of urinary flow due to prostate enlargement gives rise to symptoms of 'prostatism' that have a detrimental impact on the quality of life. The current trend in the management of symptomatic BPH favours pharmacotherapy as a first line option, while the number of surgical procedures being performed has experienced a steady decline during the last ten years. Among the pharmacological treatments, the use of alpha1-adrenoceptor blockers has demonstrated to be an effective treatment option for BPH. These agents reduce the adrenergic tone to the prostate and increase urinary flow, with a concomitant reduction of lower urinary tract symptoms. The alpha1-blockers currently approved include compounds such as alfuzosin, terazosin and doxazosin, originally developed for the treatment of hypertension, and more recently tamsulosin, an alpha1-subtype selective drug. The blockade of alpha1-adrenoceptors present in vascular smooth muscle is largely responsible for the most prominent side effects of current drugs, which can be severe and require patients dose titration. The limitation imposed by side effects naturally raises the possibility that complete blockade of prostatic alpha1 receptors is not attained at the maximum tolerated dose. The extensive efforts by the pharmaceutical industry towards the development of uroselective alpha1-blockers, is the subject of this review. Advances in the molecular cloning of genes encoding three alpha1-adrenoceptors led to the identification of the alpha1A-subtype as the predominant receptor responsible for the contraction of prostate smooth muscle. In preclinical animal models, selective alpha1A-antagonists have consistently been found to have minimal cardiovascular effects, thus providing a pharmacological rationale for uroselectivity. It has also become apparent, however, that uroselectivity can emerge in a poorly understood manner from the pharmacodynamic properties of compounds without alpha1A-subtype selectivity. Clinical experience with tamsulosin, an alpha1A/alpha1D selective drug, has failed to demonstrate a significant improvement in efficacy beyond that demonstrated for non-subtype selective alpha1-blockers, and gives support to the notion that alpha1A-selective antagonists might achieve greater efficacy for the treatment of BPH. Given the demonstrated uroselectivity of alpha1A-selective antagonists in preclinical models, it is anticipated that third generation alpha1-blockers will exhibit improved urinary flow efficacy and be better tolerated than tamsulosin. The extent to which the improvement in urinary flow will translate to the relief of symptoms of prostatism, however, remains to be demonstrated in randomised placebo-controlled clinical trials of alpha1A-selective antagonists.

Effect of JTH-601, a novel alpha1-adrenoceptor antagonist, on the function of lower urinary tract and blood pressure

In the present study, we investigated the effect of JTH-601 (3-{N-[2-(4-hydroxy-2-isopropyl-5-methylphenoxy)ethyl]-N-methylaminomethyl}-4-methoxy-2,5,6-trimethylphenol hemifumarate), a novel alpha1-adrenoceptor antagonist, in vitro and in vivo. JTH-601 (10(-9)-3 x 10(-8) M) competitively antagonized phenylephrine-induced contraction in lower urinary tract tissues (prostate, urethra and bladder trigon) in a concentration-dependent manner. The mean pA2 values for JTH-601 were 8.59+/-0.14, 8.74+/-0.09 and 8.77+/-0.11 for prostate, urethra and bladder trigon, respectively. In anesthetized rabbits, intraduodenal administration of JTH-601 (0.3-3 mg/kg), prazosin (0.03-0.3 mg/kg) and tamsulosin (0.03-0.3 mg/kg) dose dependently inhibited the phenylephrine-induced increase in urethral pressure for 3 h. Although these drugs also decreased mean blood pressure, JTH-601 was less potent than prazosin or tamsulosin. In conscious rabbits, administered JTH-601 (0.01-1 mg/kg, i.v.) had a tendency to augment orthostatic hypotension, but dose dependency was not evident. Prazosin (0.01-1 mg/kg) and tamsulosin (0.001-1 mg/kg) dose dependently augmented orthostatic hypotension. These results indicate that JTH-601 antagonized alpha1-adrenoceptor-mediated contractile responses more potently than prazosin or tamsulosin in rabbit lower urinary tract both in vitro and in vivo. JTH-601 is therefore expected to be effective in the treatment of urinary outlet obstruction in benign prostatic hypertrophy.

Dual-acting agents with alpha1-adrenoceptor antagonistic and steroid 5alpha-reductase inhibitory activities. Synthesis and evaluation of arylpiperazine derivatives

A series of arylpiperazine derivatives were prepared and evaluated for their alpha1-adrenoceptor antagonistic activities and 5alpha-reductase inhibitory activities. SAR study led to the identification of the potent dual-acting compound 2f, which had a pA2 value of 7.5 for alpha1-adrenoceptor antagonism and an IC50 value of 1.5 nM for 5alpha-reductase inhibition.

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.

Alpha-adrenergic blocking drugs in the management of benign prostatic hyperplasia: interactions with antihypertensive therapy

Management of benign prostatic hyperplasia (BPH) is often complicated by concomitant hypertension, a life-threatening condition that must be managed optimally. Many of the alpha blockers used to treat BPH also decrease blood pressure, and terazosin and doxazosin have been shown to have significant cardiovascular side effects, such as asthenia/fatigue, postural hypotension, and dizziness when used to treat BPH patients. Furthermore, these drugs are not first-line therapies for hypertension, and the majority of hypertensive BPH patients will be receiving other antihypertensive agents. Therefore, it is possible that the introduction of these drugs will affect blood pressure control, at least temporarily, with possible adverse effects. In contrast, the selective alpha1A blocker tamsulosin does not appear to have significant cardiovascular side effects and produces minimal blood pressure reductions. Therefore, urologists can choose either to use alpha blockers to treat both hypertension and BPH or to treat BPH using alpha blockers that do not interact with antihypertensive therapy. This review focuses on the alpha blockers currently being used to treat BPH, their effects on the cardiovascular system, and their interaction with antihypertensive drugs.

Alpha-adrenergic blocking drugs in clinical medicine

The alpha-adrenergic blockers have played an important role in the treatment of vascular diseases. Nonselective alpha blockers have been used as treatments for patients with severe hypertension, including pheochromocytoma. Selective alpha 1 blockers have been used in the treatment of hypertension and prostatic obstruction, and these drugs have also been considered in the treatment of other vascular and nonvascular conditions. They have unique metabolic actions, specifically on plasma lipids and lipoproteins, which could be of clinical benefit.

Ex vivo occupancy by tamsulosin of alpha1-adrenoceptors in rat tissues in relation to the plasma concentration

At 0.5-12 h after oral administration of tamsulosin (2.3 micromol/kg) in rats, there was a significant decrease in specific [3H]prazosin binding in the prostate as compared to the control value. The greater decrease occurred in the submaxillary gland. The effect of tamsulosin was mainly due to a marked reduction of [3H]prazosin binding sites (Bmax) rather than to an increase in the dissociation constant (Kd). In contrast, there was only a slight decrease or no change in the [3H]prazosin binding in the spleen, heart, and cerebral cortex of tamsulosin-administered rats at 0.5-12 h. Oral administration of terazosin (21.7 micromol/kg) significantly increased Kd values for [3H]prazosin binding with little effect on Bmax values in the rat prostate at 3 and 6 h. The greater increases in Kd values were observed in the submaxillary gland, spleen and heart at 0.5-12 h. Terazosin had a slight effect on Kd values for the cerebral cortical [3H]prazosin binding. Tamsulosin was absorbed rapidly after oral administration at a dose of 2.3 micromol/kg in rats, and at 6 h, plasma concentration decreased markedly to approximately one-twentieth of the 0.5 h peak level. alpha1-Adrenoceptor occupancy was estimated as a percentage of decrease in Bmax values for [3H]prazosin binding in tissues of tamsulosin-treated rats compared with control rats. The alpha1-adrenoceptor occupancy by tamsulosin in the prostate and submaxillary gland occurred rapidly in parallel with the rise in plasma concentration of tamsulosin, and lasted for over 12 h despite the marked decrease in plasma concentration. Consequently, it is suggested that tamsulosin produces more selective and sustained occupancy in vivo of alpha1-adrenoceptors in the submaxillary gland and prostate of rats than in other tissues.

Synthesis of benzanilide derivatives as dual acting agents with alpha 1-adrenoceptor antagonistic action and steroid 5-alpha reductase inhibitory activity

Synthesis of benzanilide derivatives which have dual alpha 1-adrenoceptor antagonistic action and steroid 5 alpha-reductase inhibitory activity and their structure-activity relationships is described.

In vivo receptor binding of novel alpha1-adrenoceptor antagonists for treatment of benign prostatic hyperplasia

New types of alpha1-adrenoceptor antagonists (tamsulosin, KMD-3213 and JTH-601) are currently receiving a great deal of attention, especially in terms of developing effective therapeutic agents to treat bladder outlet obstruction with less side effects, such as postural hypotension, in patients with benign prostatic hyperplasia (BPH). In vivo alpha1-adrenoceptor binding properties of these antagonists in prostate and other tissues of rats were examined. Intravenous injections of tamsulosin, KMD-3213 and JTH-601 inhibited dose-dependently in vivo specific [3H]tamsulosin binding in various tissues. Ratios of ID50(aorta) to ID50(prostate) of KMD-3213 and JTH-601 were greater than those of tamsulosin and prazosin. Further, the ratios of ID50(spleen) to ID50(submaxillary gland) of these drugs were greater than that of prazosin. Following intravenous injections of [3H]KMD-3213 in rats, the amount of specific binding in prostate was significantly greater than that of [3H]prazosin, but that in aorta or spleen was much smaller. Interestingly, [3H]JTH-601 showed little in vivo specific binding in aorta. These data suggest that KMD-3213 and JTH-601 exhibit higher affinity to alpha1-adrenoceptors in prostate and submaxillary gland than in vascular tissues in vivo.

Overview of alpha-blocker therapy for benign prostatic hyperplasia

Management of benign prostatic hyperplasia (BPH) is rapidly changing. Established surgical procedures are being replaced by minimally invasive modalities such as electrovaporization and transurethral needle ablation. Improved understanding of pathophysiology and developments in molecular biology has provided drugs for alleviating the symptoms of prostatic enlargement. Currently, medical therapy is the first-line treatment modality in the management of BPH. There are two types of medical treatment available: alpha-adrenoceptor-blockers and 5-alpha-reductase inhibitors. Alpha-blockers relieve the dynamic component of obstruction whereas 5-alpha-reductase inhibitors relieve the mechanical component of obstruction. At present, alpha-blockers are used most frequently. However, they do have significant cardiovascular side effects. More uroselective alpha-blockers have recently become available and may reduce the risk of cardiovascular side effects. This review summarizes relevant literature on the use of alpha-blockers in the treatment of BPH.

Urodynamic effects of various treatment modalities for benign prostatic hyperplasia

PURPOSE

I studied the effects of various treatments for benign prostatic hyperplasia on urethral resistance.

MATERIALS AND METHODS

I reviewed the literature on urodynamic effects of treatments for benign prostatic hyperplasia. Articles that reported pretreatment and posttreatment values of relevant urodynamic parameters were analyzed. Average before and after treatment values of maximum flow rate and detrusor pressure at maximal flow rate for every study were plotted on an Abrams-Griffiths nomogram and classified as obstructed, equivocal or nonobstructed. Average values of maximum flow rate and detrusor pressure at maximal flow rate were calculated for the total number of patients treated by a certain modality.

RESULTS

Based on this analysis, the rank order of urodynamic efficacy was that open prostatectomy is more effective in reducing urethral resistance than is transurethral prostatectomy. These treatments diminish obstruction better than laser treatment or transurethral incision of the prostate, which again are more effective than balloon dilation, alpha-blockers or transurethral microwave thermotherapy. Finally, androgen deprivation performs better than placebo treatment.

CONCLUSIONS

The rank order of urodynamic efficacy as determined in this analysis shows a high level of agreement with reported rank order of symptomatic efficacy of various modalities. After placebo treatment there is no significant change in urethral resistance. This finding indicates that pressure-flow studies are a sensitive way to compare active to placebo treatment and that pressure-flow studies have excellent long-term reproducibility.

Functional property, norepinephrine content and morphometric findings in human hyperplastic prostate

BACKGROUND

Although alpha-adrenergic blockers are widely used as a treatment of benign prostatic hyperplasia (BPH), it is not clear whether contractile property of hyperplastic prostate to alpha-adrenergic agonist depends upon an area of density of smooth muscle within the respective BPH tissue.

METHODS

Functional study and quantitative morphometric analysis were performed on human prostatic specimens obtained by transurethral resection from 22 men with symptomatic BPH. Tissue norepinephrine content was also evaluated.

RESULTS

There was a linear correlation between the area of density of smooth muscle and maximum response to phenylephrine (r = 0.457, P = 0.0362). Although the area of density of smooth muscle showed a positive correlation with norepinephrine content (r = 0.437, P = 0.0471), norepinephrine content was not correlated with maximum phenylephrine response.

CONCLUSIONS

Contractile response to alpha-adrenergic agonist was directly influenced by the area of density of the smooth muscle within an individual prostate.

N-arylpiperazinyl-N'-propylamino derivatives of heteroaryl amides as functional uroselective alpha 1-adrenoceptor antagonists

Novel arylpiperazines were identified as alpha 1-adrenoceptor (AR) subtype-selective antagonists by functional in vitro screening. 3-[4-(ortho-Substituted phenyl)piperazin-1-yl]propylamines were derivatized with N,N-dimethyl anthranilamides, nicotinamides, as well as carboxamides of quinoline, 1,8-naphthyridine, pyrazolo[3,4-b]pyridine, isoxazolo[3,4-b]pyridine, imidazo[4,5-b]pyridine, and pyrazolo[1,5-a]pyrimidines. Strips of rabbit bladder neck were employed as a predictive assay for antagonism in the human lower tract. Rings of rat aorta were used as a "negative screen" for the test antagonists. Binding to alpha 1-ARs was relatively sensitive to size and electronic features of the arylpiperazine portion of the antagonists and permissive to these features on the heteroaryl carboxamide side. These structure-affinity findings were exploited to produce nicotinamides (e.g. 13ii and 25x) and pyrazolo[3,4-b]pyridines (e.g. 37f and 37y) ligands with nanomolar affinity at the alpha 1-AR subtype prevalent in the human lower urinary tract(pA2 values: 8.8, 10.7, 9.3, and 9.9, respectively) and displaying 2-3 orders of magnitude selectivity over the alpha 1D-AR.

Doxazosin in men with lower urinary tract symptoms: urodynamic evaluation at 15 months

OBJECTIVES

To assess the results of doxazosin treatment in men with lower urinary tract symptoms (LUTS) treated for 15 months and to correlate symptomatic changes with alterations in urodynamic measures.

METHODS

After an initial 3-month treatment period with doxazosin 4 mg/day, 50 men with LUTS were given the choice of continued treatment with this agent or other therapeutic options. All patients were evaluated by International Prostate Symptom Score (IPSS) questionnaires and urodynamic evaluation initially and after 3 months of treatment. Patients were followed for an additional 12 months and those who continued doxazosin treatment underwent repeat urodynamic testing.

RESULTS

Among the original 50 patients, 24 men (48%) continued doxazosin treatment for 15 months, 18 men (36%) discontinued therapy, and 8 men (16%) were either dead or lost to follow-up or had been diagnosed and treated for prostate cancer. Comparison of values at 3 and 15 months of follow-up (9.4 versus 13.4, P = 0.03) showed significant worsening of voiding symptoms, as assessed by the IPSS, in the 24 men still receiving doxazosin. This deterioration of subjective results with doxazosin occurred despite continued improvements in peak urinary flow rate (Qmax), detrusor pressure at peak flow (PdetQmax), and objective measures of obstruction (Abrams-Griffiths number) from 3 to 15 months of follow-up.

CONCLUSIONS

Relief of voiding symptoms in men with LUTS treated with doxazosin over prolonged intervals of 15 months does not correlate well with changes in urodynamic measures.

Clinical Experiment Comparing 3 Pharmacological Treatments of Benign Prostatic Hypertrophy: Terazosin Vs. Finasteride Vs. Terazosin + Finasteride

The tone of the smooth prostate muscle and the presence of hyperplastic tissue represent the dynamic and passive components respectively of the obstructive symptomatology present in benign prostatic hyperplasia (BPH). The contractile properties are mediated primarily by the alpha-1 type adrenergic receptors, which are found in great numbers in the stroma of the gland and in the prostatic capsule. The use of Terazosin, a selective alpha-1 blocker, has proved to be effective in the improvement of BPH symptoms associated with the hypertone of the smooth muscle. The assumption that androgens play an important role in hypertrophy of the prostate has introduced drugs into the treatment which are capable of blocking the synthesis and the action of testosterone and, in particular, dihydrotestosterone (DHT). Finasteride is an inhibitor of 5-alpha-reductase, the enzyme inside the prostatic epithelial cells which converts the testosterone into DHT. A multicentre study has therefore been carried out aimed at assessing, after 9 months treatment, the efficacy and tolerability of three pharmacological treatments: Terazosin, Finasteride and a combination of the two, in 146 patients with symptomatic BPH. Results of the study indicate that the drugs were well tolerated and that the efficacy in resolving the obstructive symptomatology was particularly accentuated and rapid in the groups treated with Terazosin, the action of which, in this respect, has proved to be more significant than that of Finasteride.

Prostatic alpha 1-adrenoceptors and uroselectivity

BACKGROUND

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

METHODS

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

CONCLUSIONS

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

Effect of the alpha-1 adrenoceptor blocker on tissue norepinephrine contents in human benign prostatic hyperplasia

To see the effect of the alpha-adrenergic blocking agent on tissue norepinephrine contents of the prostate, norepinephrine (NE) levels were investigated in patients with symptomatic benign prostatic hyperplasia (BPH). Morphometrical analyses were also performed to detect the differences in tissue composition. Nineteen patients were subdivided into two groups. Patients in Group 1 were given tamsulosin hydrochloride (0.2 mg/day) for at least 4 weeks before transurethral resection of the prostate (TURP), while patients in the control group (Group 2) underwent no previous treatment for BPH before TURP. Tissue NE contents were investigated by high performance liquid chromatography on a chip of the prostate obtained by TURP. These two groups were closely similar in age distribution, prostatic size, results of preoperative symptom scoring and relative proportion of smooth muscle component within the evaluated specimen. In the present series, tissue NE contents in these groups were not statistically different (p = 0.64). Chronic and acute administration of the alpha-1 antagonist did not apparently influence the tissue NE level in patients with BPH.

Comparison of the antagonistic activity of tamsulosin and doxazosin at vascular alpha 1-adrenoceptors in humans

alpha 1-Adrenoceptor blockers such as prazosin and doxazosin are used to treat hypertension as well as benign prostatic hyperplasia (BPH), whereas the new alpha 1-adrenoceptor blocker tamsulosin is used only for BPH and does not reduce blood pressure at the doses used to relax prostatic smooth muscle. In contrast to prazosin, tamsulosin has a higher affinity for prostatic than vascular alpha 1-adrenoceptors in vitro. The functional correlate of this observation in humans is the subject of this study. The alpha 1-adrenoceptor blockade by oral tamsulosin (0.2 mg), doxazosin (1 mg) or placebo on finger tip vascular and dorsal hand venous alpha 1-adrenoceptors stimulated by cold treatment (immersion in ice water) and the alpha 1-adrenoceptor agonist phenylephrine, was thus studied in a 3-way crossover study in eight, healthy, male adults. Finger tip vasoconstriction after cold stimulation was assessed by laser Doppler flowmetry. A linear variable differential transformer was used to assess the drug effect on phenylephrine-induced venoconstriction. All study parameters were assessed at around 2 and 3.5 h after oral intake of doxazosin and tamsulosin respectively. The drug plasma levels were not significantly different. No significant differences were found for blood pressure or heart rate in the three treatments in supine and erect position. The reduction in finger tip blood flow after cold stimulation was significantly smaller after doxazosin treatment (P < 0.01) than after tamsulosin or placebo, whereas there was no significant difference between tamsulosin and placebo treatments. The infusion rate of phenylephrine producing a half-maximum venoconstriction was significantly larger after doxazosin than after tamsulosin (P < 0.05) or placebo (P < 0.01), whereas there was again no significant difference between tamsulosin and placebo treatments. The data suggest that, at doses producing equal plasma levels after single oral doses in human subjects, the blocking activity at vascular alpha 1-adrenoceptors is lower for tamsulosin than for doxazosin.

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.

Correlation between morphometric differences and norepinephrine content in benign prostatic hyperplasia

Tissue norepinephrine (NE) content and quantitative morphometric analysis of benign prostatic hyperplasia (BPH) were evaluated in 30 patients with symptomatic BPH. BPH specimens were obtained by transurethral resection, and NE content was evaluated by high-performance liquid chromatography. The proportions of smooth muscle fibrous, and glandular elements were determined by the light microscopic stereological method. Norepinephrine content of the prostate correlated well with the proportion of smooth muscle component (r = 0.749, P < 0.0001). The percentage of fibrous tissue element was positively correlated with prostate size (r = 0.459, P = 0.0099). Norepinephrine content and histological components did not correlate with subjective symptom score. Morphometrical findings and NE content did not correlate with uroflowmetry parameters and postvoid residual urine rate. In conclusion, NE content of the prostate was probably determined by the amount of smooth muscle element in BPH tissue. The fibrous tissue element was increased in large hyperplastic tissue. The severity of BPH could not be explained by differences in histological composition alone.

A multicenter, randomized, double-blind, placebo-controlled study to evaluate the safety and efficacy of terazosin in the treatment of benign prostatic hyperplasia

OBJECTIVES

This study was designed to evaluate the safety and efficacy of the selective alpha 1-adrenoceptor blocker terazosin in the treatment of benign prostatic hyperplasia (BPH).

METHODS

Two hundred twenty-four patients aged 50 to 80 years, who had a diagnosis of BPH based on medical history, physical examination, and digital palpation, were recruited from 11 different sites between January 1992 and January 1994. The study consisted of a screening phase, a placebo phase, a double-blind dose-titration phase, and a double-blind maintenance phase.

RESULTS

Of the patients recruited, 164 entered the double-blind phase and of these 134 were evaluable. Only 11 patients withdrew because of an adverse event, 7 in the terazosin and 4 in the placebo group. Compared to placebo, terazosin significantly increased peak and mean urine flow rates without significantly affecting voided volume or postvoid residual volume. It significantly improved both the obstructive and irritative symptoms associated with BPH. Fifty-one patients from the terazosin group reported a total of 120 adverse events compared with 83 reported by 42 patients in the placebo group. The majority of these events were mild to moderate. Seventeen terazosin-treated patients reported hypotension-related adverse events and 4 withdrew from the study. However, concurrent treatment with antihypertensive agents did not affect the blood pressure response of the terazosin group.

CONCLUSIONS

Overall, this study showed terazosin to be safe and effective in relieving the signs and symptoms of BPH and should be considered as a treatment alternative.

Prostatism: benign prostatic hyperplasia

This article is devoted to the most common cause of outlet obstruction in the male geriatric population, benign prostate hyperplasia (BPH). The prevalence, pathophysiology, and natural history of BPH is discussed, along with the work-up and indications for medical or surgical intervention. The authors also focus on medical and surgical options now available for management of BPH.

Determination of alpha 1-adrenoceptor antagonists in plasma by radioreceptor assay

A simple, rapid and sensitive radioreceptor assay (RRA) for the quantification of alpha 1-adrenoceptor antagonists such as prazosin in plasma is described. The method involves the use of an RRA based on [3H]prazosin displacement in rat cerebral cortical membranes. The method is reliable, with intra-assay and inter-assay RSDs ranging from 5.9 to 9.2%. The limit of detection is 0.2 (prazosin hydrochloride), 0.05 (tamsulosin hydrochloride) and 0.3 (bunazosin hydrochloride) pmol per assay. Using this method the plasma levels of prazosin hydrochloride were determined in beagle dogs administered orally 2.39 mumol kg-1 of this drug. The plasma levels of prazosin in beagle dogs are in good agreement with those obtained using a high-performance liquid chromatography (HPLC). This RRA proved to be applicable to the monitoring of plasma prazosin levels in patients with essential hypertension and/or benign prostatic hypertrophy receiving therapy with this drug with the therapeutic dosage schedule. Thus, the concentrations of alpha 1-adrenoceptor antagonists in plasma can be adequately monitored by RRA as well as by HPLC.

Norepinephrine contents of human prostatic hyperplasia: differences between pathological subtypes

Tissue norepinephrine content in benign prostatic hyperplasia (BPH) was evaluated to detect possible histological differences in BPH subtypes and to investigate the correlation between norepinephrine levels and age, prostatic weight and clinical symptom score, respectively. Specimens were obtained from 28 patients who underwent transurethral resection of the prostate. Pathologically, 18 out of 28 specimens were classified as fibromyoadenomatous hyperplasia and the remaining 10 as fibromuscular type. Norepinephrine content in the fibromyoadenomatous type was 133.1 +/- 23.1 ng/g, whereas it was 340.3 +/- 60.5 ng/g in the fibromuscular type. Norepinephrine level in the former group was significantly lower than that in the latter group (p < 0.001). In both groups, there was no correlation between norepinephrine content, age and clinical symptom score, while the norepinephrine content had a reverse correlation with prostatic weight only in the former group (p < 0.05). In conclusion, norepinephrine levels were dependent upon histological differences, especially upon the amount of smooth muscle elements, in the evaluated specimen. Severity of prostatism and patients' age showed no correlation with tissue norepinephrine content.