A Selective α1A-Adrenoceptor Antagonist Inhibits Detrusor Overactivity in a Rat Model of Benign Prostatic Hyperplasia

Additive effect of oral LDD175 to tamsulosin and finasteride in a benign prostate hyperplasia rat model

Objective

We investigated the benefits of the BK_Ca agonist 4-chloro-7-trifluoromethyl-10H-benzo[4,5]furo[3,2-b]indole-1-carboxylic acid (LDD175) combined with tamsulosin and finasteride, in a benign prostatic hyperplasia (BPH) rat model.

Materials and methods

Castration was performed by bilateral orchiectomy under ketamine anesthesia. A rat model of BPH was established by daily intramuscular administration of testosterone propionate plus 17β-estradiol for 8 weeks. Model rats were administered combinations of 20 mg/kg LDD175, 0.01 mg/kg tamsulosin and 1 mg/kg finasteride once daily by oral gavage for 4 weeks from week 6 to 9 post-surgery. Intraurethral pressure induced by electrostimulation of the hypogastric nerve was measured at the end of administration. Body and genitourinary organ weights were recorded, serums were assayed for hormone concentrations, and tissues were subjected to histopathology, and analyses of α1-adrenoceptor mRNA and protein expression levels after treatment.

Results

Combined LDD175, tamsulosin, and finasteride significantly decreased prostatic index, serum hormone levels, epithelial thickness, and prostate expression of α1-adrenoceptors in BPH model rats. The 3-drug combination was more effective than any other combination or LDD175 alone.

Conclusion

These results suggest that LDD175 addition to tamsulosin and finasteride may be beneficial for the treatment of BPH patients who do not respond to tamsulosin plus finasteride.

Functional roles of bladder α1-adrenoceptors in the activation of single-unit primary bladder afferent activity in rats

OBJECTIVES

To clarify the involvement of bladder α1-adrenoceptors (α1-ARs) in afferent pathways by investigating the effects of silodosin and BMY7378, selective α1A- or α1D-AR antagonists, respectively, on single-unit afferent nerve fibre activity (SAA) of the primary bladder afferent nerves and their relationship with bladder microcontractions in rats.

MATERIALS AND METHODS

A total of 63 female Sprague-Dawley rats were anaesthetized with urethane. The SAA of Aδ and C fibres generated from the left L6 dorsal roots was determined using electrical stimulation of the left pelvic nerve and bladder distension. After measuring baseline SAA during constant filling cystometry, the procedure was repeated with i.v. (0.3-30 μg/kg) or intravesical (10 μm) administration of each antagonist. In separate rats, the bladder was filled with saline until the intravesical pressure reached 30 cmH2 O, and was kept under isovolumetric conditions, then the recording was performed with i.v.-administered vehicle and silodosin (0.3 μg/kg).

RESULTS

A total of Aδ fibres and 33 C fibres were isolated from 63 rats. The SAA of Aδ fibres, but not C fibres, were dose-dependently decreased after both i.v. and intravesical administrations of each of the antagonists. In the experiments under bladder isovolumetric conditions, silodosin administration significantly decreased the SAA of Aδ fibres, but not C fibres, compared with vehicle administration. There were no significant effects on either the mean basal bladder pressure or microcontractions.

CONCLUSION

The present study suggests that both α1A- or α1D-ARs in the rat bladder are involved in the activation of the bladder mechanosensory Aδ fibres during bladder filling, and that this activation may not be related to bladder microcontractions.

[Physiopathology of overactive bladder syndrome]

The pathophysiology of OAB is complex, multifactorial and still largely unknown. Several pathophysiological mechanisms have been highlighted that may play a different role in different patient groups. There are now experimental evidences that support both the myogenic and neurogenic hypothesis, but in recent years the "integrative" hypothesis has been gaining more and more acceptance, where a disruption in the multiple interactions between different cell types (neurons, urothelium, interstitial cells, myocytes) and network functions represent a central element of lower urinary tract dysfunctions. Of utmost importance, a disorder in the urothelial sensory function and in the urothelial/suburothelial non-neural cholinergic system, favored by age and comorbidities, appears to be crucial for the development of the OAB. Neuroplastic and detrusor changes in OAB are broadly similar to those observed in bladders exposed to outlet obstruction, neuropathies, inflammation or aging, and may be driven by a common urothelial dysfunction. Several signaling substances and their receptors were found to be involved in central pathways of bidirectional communication between the different cell types in the bladder, and were shown to be modified in several animal models of OAB as well as in human models, indicating new potential therapeutic targets.

Effects of Silodosin, an α1A-Adrenoceptor Antagonist, and Distigmine, an Acetylcholinesterase Inhibitor, and Their Combined Effects on Impaired Voiding Function in Zucker Diabetic Fatty Rats

BACKGROUND/AIMS

To evaluate the effects of silodosin (α1A-adrenoceptor antagonist) and distigmine (acetylcholinesterase inhibitor), alone or in combination, on voiding dysfunction in Zucker diabetic fatty (ZDF) rats, a type 2 diabetes model, by pressure flow study.

METHODS

Male ZDF rats were anesthetized with urethane and a catheter was implanted into the bladder through the dome. Saline was continuously infused into the bladder at 6 ml/h to induce the micturition reflex. Intravesical pressure and micturition volume were recorded continuously and various urodynamic parameters were calculated using a waveform analysis system.

RESULTS

Increased bladder capacity, residual volume, and urethral resistance and decreased maximum detrusor contraction velocity and urine flow rate, considered to be detrusor underactivity-like symptoms, were observed in ZDF rats. Although both silodosin and distigmine improved impaired voiding function, administration of both drugs in combination was more effective than either drug alone.

CONCLUSIONS

ZDF rats showed symptoms suggestive of detrusor underactivity, and silodosin tended to ameliorate these symptoms in ZDF rats. These results suggested that an α1A-adrenoceptor antagonists may be effective against the voiding disorder accompanying not only bladder outlet obstruction but also deficiency of bladder function. Moreover, combined administration of an α1A-adrenoceptor antagonist with an acetylcholinesterase inhibitor may have additive efficacy in clinical use.

Impact of a folic acid-enriched diet on urinary tract function in mice treated with testosterone and estradiol

Aging men are susceptible to developing lower urinary tract symptoms, but the underlying etiology is unknown and the influence of dietary and environmental factors on them is unclear. We tested whether a folic acid-enriched diet changed urinary tract physiology and biology in control male mice and male mice with urinary dysfunction induced by exogenous testosterone and estradiol (T+E2), which mimics changing hormone levels in aging humans. T+E2 treatment increased mouse urine output, time between voiding events, and bladder capacity and compliance. Consumption of a folic acid-enriched diet moderated these changes without decreasing prostate wet weight or threshold voiding pressure. One potential mechanism for these changes involves water balance. T+E2 treatment increases plasma concentrations of anti-diuretic hormone, which is offset at least in part by a folic acid-enriched diet. Another potential mechanism involves neural control of micturition. The folic acid-enriched diet, fed to T+E2-treated mice, increased voiding frequency in response to intravesicular capsaicin infusion and increased mRNA abundance of the capsaicin-sensitive cation channel transient receptor potential vanilloid subfamily member 1 (Trpv1) in L6 and S1 dorsal root ganglia (DRG) neurons. T+E2 treatment and a folic acid-enriched diet also modified DNA methylation, which is capable of altering gene expression. We found the enriched diet increased global DNA methylation in dorsal and ventral prostate and L6 and S1 DRG. Our results are consistent with folic acid acting to slow or reverse T+E2-mediated alteration in urinary function in part by normalizing water balance and enhancing or preserving afferent neuronal function.

Controlled release of dutasteride from biodegradable microspheres: in vitro and in vivo studies

The aim of the present work was to study the in vitro/in vivo characteristics of dutasteride loaded biodegradable microspheres designed for sustained release of dutasteride over four weeks. An O/W emulsion-solvent evaporation method was used to incorporate dutasteride, which is of interest in the treatment of benign prostatic hyperplasia (BPH), into poly(lactide-co-glycolide) (PLGA). A response surface method (RSM) with central composite design (CCD) was employed to optimize the formulation variables. A prolonged in vitro drug release profile was observed, with a complete release of the entrapped drug within 28 days. The pharmacokinetics study showed sustained plasma drug concentration-time profile of dutasteride loaded microspheres after subcutaneous injection into rats. The in vitro drug release in rats correlated well with the in vivo pharmacokinetics profile. The pharmacodynamics evaluated by determination of the BPH inhibition in the rat models also showed a prolonged pharmacological response. These results suggest the potential use of dutasteride loaded biodegradable microspheres for the management of BPH over long periods.

[New treatment strategies for male lower urinary tract symptoms]

For patients with lower urinary tract symptoms (LUTS), α1-adrenoreceptor inhibitors and 5-alpha reductase inhibitors as well as their combination are considered the gold standard. In addition, anticholinergic agents are being introduced as monotherapy or in combination with α1-adrenocepetor inhibitors for patients with predominant storage disorders. Phosphodiesterase 5 (PDE5) inhibitors are often the best option for patients with LUTS who also suffer from erectile dysfunction. Recently, novel treatment options have been presented and intraprostatic injection of various agents, such as botulinum toxin A, NX-1207 and PRX302 has shown promising initial results. In addition, innovative minimally invasive treatment options, such as UroLift® appear to be efficacious and safe in this patient cohort. Particular emphasis should be laid on patients with LUTS and concomitant sexual disorders.

Safety and pharmacokinetic studies of silodosin, a new α1A-adrenoceptor selective antagonist, in healthy Chinese male subjects

The objectives of the study were to assess the safety and pharmacokinetics of silodosin capsules in 82 healthy male Chinese subjects. To evaluate the safety after single-dosing escalation, 40 subjects were equally divided into 4 groups (2, 4, 8, 12 mg) by a randomized, double-blind and placebo-controlled design. To assess the pharmacokinetics after single-dosing, 30 subjects were equally divided into 3 groups (4, 8, 12 mg). To assess the safety and pharmacokinetics via multiple-dosing, 12 subjects were included as a group (4 mg once daily at day 1 and day 7; 4 mg twice daily at day 2 through day 6). The safety observations showed that mild adverse events, including postural hypotension, dizziness, and headache, were observed. After single-dosing at doses of 4, 8, and 12 mg, the mean area under the concentration-time curve from 0 to 36 h (AUC(0-36)) values were 136.82±46.38, 270.17±54.66, and 474.63±108.50 µg/l·h and the mean maximal silodosin concentration in plasma (C(max)) values were 26.70±7.48, 48.47±12.35, and 94.07±22.59 µg/l, respectively. After multiple-dosing, the C(max) value at day 7 was 33.84±19.54 µg/l, and the AUC(0-24) value at day 7 was 193.19±68.96 µg/l·h. The accumulation ratio of the AUC value was 1.55 by comparing the multiple-dosing with the single-dosing. It is concluded that silodosin is safe and tolerated in healthy Chinese male subjects at the dosing levels used in this study. The mean C(max) and AUC values of silodosin increased proportionally with dose escalation, showing characteristics of linear pharmacokinetics.

Urodynamic effects of silodosin, a new alpha 1A-adrenoceptor selective antagonist, for the treatment of benign prostatic hyperplasia

AIMS

To investigate urodynamically the effects of silodosin, a new alpha(1A)-adrenoceptor-selective antagonist, in the treatment of benign prostatic hyperplasia (BPH).

METHODS

Thirty six male patients with BPH (69.9 +/- 7.3 years), who were referred as candidates for surgery, were treated with silodosin (4 mg twice daily). The total International Prostate Symptom Score (IPSS) was 20.7 +/- 7.4, maximum flow rate (Q(max)) was 6.7 +/- 3.0 ml/sec, and prostate volume was 45.6 +/- 24.5 ml.

RESULTS

Total IPSS, storage and voiding symptom subscores and QOL score decreased significantly, and Q(max) increased significantly after 1-12 months of therapy (all P < 0.05). In urodynamic study (n = 29), maximum cystometric capacity increased significantly (P = 0.0027), and detrusor overactivity disappeared in 8 of 20 patients (40%) and improved (bladder capacity increased more than 50%) in 7 (35%) after the therapy. In pressure/flow studies (n = 27), the obstruction grade was improved in 15 patients (56%). Detrusor opening pressure, detrusor pressure at Q(max), bladder outlet obstruction index, and Schäfer's obstruction class decreased significantly after therapy (all P < 0.01). After 12 months, 16 patients (44%) are still on silodosin for 23.3 +/- 7.0 (range 12-36) months, and the improvements in IPSS and Q(max) were stable. Twenty patients withdrew because of insufficient effectiveness in 13 patients (12 patients underwent surgery), side effects in 3, and unknown reasons in 4.

CONCLUSION

Silodosin appears to improve detrusor overactivity and obstruction grade in patients with BPH. With silodosin treatment, LUTS could be managed effectively for more than a year in at least 44% of the patients.

Effects of Silodosin on Lower Urinary Tract Symptoms in Patients with Benign Prostatic Hyperplasia: Evaluation by Frequency/Volume Chart

OBJECTIVES

To prospectively evaluate the efficacy of silodosin, a new α1A -adrenoceptor selective antagonist, for the treatment of lower urinary tract symptoms suggestive of benign prostatic hyperplasia (LUTS/BPH) on the basis of a frequency/volume chart.

METHODS

Forty male patients (71.1 ± 6.6 years old) with LUTS/BPH were treated with silodosin (4 mg twice daily). The effects of the drug were assessed by changes in International Prostate Symptom Score, uroflowmetry, and frequency/volume chart at 1 and 3 months after therapy.

RESULTS

The mean total International Prostate Symptom Score, the mean total storage and voiding scores and the mean quality of life score decreased significantly at 1 and 3 months after therapy (all P < 0.01). Average and maximum flow rates increased significantly, and postvoid residual volume decreased significantly after 1 and 3 months (all P < 0.05). The frequency/volume chart showed that daytime frequency in those who initially voided over eight times/day (n = 12) decreased significantly (P = 0.0391) after 1 month, and nighttime frequency in those who initially voided over two times (n = 16) tended to decrease (P = 0.0833) after 3 months. Mean voided volume in those who initially voided less than 250 mL (n = 31) increased significantly after 1 and 3 months (P = 0.0446 and P = 0.0138, respectively), and maximum voided volume in those who initially voided less than 300 mL (n = 18) tended to increase (P = 0.0833) after 1 month.

CONCLUSION

Silodosin appears to be effective for both storage and voiding symptoms by increasing bladder capacity in patients with LUTS/BPH.

Management of benign prostatic hyperplasia with silodosin

It has been reported that blockade of α1A-adrenoceptor (AR) relieves bladder outlet obstruction, while blockade of α1D-AR is believed to alleviate storage symptoms due to detrusor overactivity. Silodosin, (-)-1-(3-hydroxypropyl)-5-[(2R)-2-({2-[2-(2,2,2trifluoroethoxy) phenoxy]ethyl}amino)propyl]-2,3-dihydro-1H-indole-7- carboxamide, is a new α1A-AR selective antagonist. Silodosin is highly selective for the α1A-AR subtype, showing an affinity for the α1A-AR that is 583- and 55.5-fold higher than its affinity for the α1B-and α1D-ARs, respectively. In randomized, double-blind, placebo-controlled phase III studies performed in Japan and the United States, silodosin has been shown to be effective for both storage and voiding symptoms associated with benign prostatic hyperplasia. Early effects of silodosin (after 2-6 hours or day 1) on lower urinary tract symptoms have also been reported. In urodynamic studies, detrusor overactivity disappeared in 40% and improved in 35% of patients after administration. In pressure flow studies, the grade of obstruction on the International Continence Society nomogram showed improvement in 56% of patients. The rate of adverse events in the silodosin, tamsulosin and placebo groups was 88.6%, 82.3%, and 71.6%, respectively. The most common adverse event was (mostly mild) abnormal ejaculation (28.1%). However, few patients (2.8%) discontinued silodosin because of abnormal ejaculation. Orthostatic hypotension showed a similar incidence in the silodosin (2.6%) and placebo (1.5%) groups. In conclusion, silodosin improves detrusor overactivity and obstruction and thus may be effective for both storage and voiding symptoms in patients with benign prostatic hyperplasia.

Silodosin: an orally active selective α1-adrenoceptor antagonist for benign prostatic hyperplasia

α1-adrenoceptor antagonists play a central role in the treatment of uncomplicated symptomatic benign prostatic hyperplasia, frequently in combination with the 5-α-reductase inhibitors such as finasteride and dutasteride. Clinically useful examples include alfuzosin, doxazosin, tamsulosin and terazosin. These can be subdivided into nonselective (doxazosin and terazosin) and uroselective (alfuzosin and tamsulosin) agents. In general, these agents appear to be equieffective. However, they can be distinguished on the basis of their adverse event profiles. Such adverse events include those due to their vasodilatory effects (dizziness, orthostatic hypotension and rhinitis), genitourinary effects (ejaculatory dysfunction) and nonspecific effects (e.g., asthenia, malaise and gastrointestinal upset). A new α1A-adrenoceptor antagonist, silodosin, has recently been approved. In most ways, it is similar to tamsulosin in its pharmacodynamic effects in vitro and in vivo (in both animals and humans). Limited clinical trial data have shown silodosin to significantly improve lower urinary tract symptoms associated with benign prostatic hyperplasia and quality of life, with effects sustainable for at least 1 year. Its adverse-event profile reflects that seen with other uroselective α-adrenoceptor antagonists with the exception of a relatively high-incidence rate of ejaculatory dysfunction (22 vs 2% with tamsulosin and 28 vs 1% with placebo). This article reviews the preclinical and clinical data concerning silodosin and introduces the reader to this new drug for the treatment of benign prostatic hyperplasia.

Lower urinary tract symptoms after hormone replacement therapy in Japanese patients with late-onset hypogonadism: a preliminary report

Hormone replacement therapy (HRT) is performed for the treatment for patients with late onset hypogonadism (LOH). One of the main concerns about HRT is the influence of lower urinary tract including prostate. This study examined whether HRT for Japanese patients of LOH affected lower urinary tract symptoms. A total of 21 patients with LOH were included in this study. Changes of International prostate symptom score (IPSS), IPSS quality of life (QOL) index and King's health questionnaire (KHQ), before HRT and 3 months after HRT, were evaluated. Statistical comparisons were made using the Wilcoxon signed rank test, P < 0.05 was considered statistically significant. Total IPSS and QOL index were not significantly different from 7.43 +/- 6.56, 2.71 +/- 1.74 at baseline to 8.29 +/- 6.24, 2.91 +/- 1.13 after 3 months. There were no significant differences in any of the nine categories of KHQ. In this preliminary study, the results suggested that HRT for LOH had no short-term effects on patients with lower urinary symptoms.

Early efficacy of silodosin in patients with lower urinary tract symptoms suggestive of benign prostatic hyperplasia

OBJECTIVES

To evaluate the early efficacy of the alpha(1A)-adrenoceptor selective drug, silodosin, for the treatment of lower urinary tract symptoms suggestive of benign prostatic hyperplasia.

METHODS

A total of 68 patients with an International Prostate Symptom Score (IPSS) of >==8 and a Quality of Life (QOL) index of >==2 were included. Changes in the IPSS and QOL index were evaluated before and after 1, 2, 3, 4, 5, 6, 7, 14, and 28 days of twice daily oral administration of 4 mg silodosin. Next, changes in IPSS subscores as well as voiding, storage, and post micturition symptoms were assessed. Changes in total IPSS based on symptom severity were also determined.

RESULTS

Total IPSS and QOL index improved significantly from 19.38 +/- 7.46, 4.68 +/- 1.07 at baseline to 15.81 +/- 7.40, 4.22 +/- 1.30 at day 1. The subscores of voiding, storage, and post micturition symptoms were significantly decreased from 8.93 +/- 3.95, 7.97 +/- 3.88, and 2.49 +/- 1.70 at baseline to 7.28 +/- 4.09, 6.52 +/- 3.47, and 2.02 +/- 1.56 at day 1, respectively. This trend continued throughout the study. Regardless of severity, total IPSS were significantly decreased at day 1 and maintained throughout the study.

CONCLUSIONS

Silodosin may be considered a promising treatment for benign prostatic hyperplasia/lower urinary tract symptom patients.

Developments in the pharmacotherapy of the overactive bladder

PURPOSE OF REVIEW

The overactive bladder is a common and distressing condition that has a significant impact on the quality of life of many people worldwide. Anticholinergics remain the first line in pharmacotherapy, however the use of these agents is hindered by adverse effects and limited efficacy. Thus there is a need for more effective treatments. Recently, there has been a move towards targeting novel pathways thought to play a role in overactivity. This review aims to provide an insight into the recent developments in pharmacotherapy of the overactive bladder.

RECENT FINDINGS

With recent advances in our understanding of the basic science of the overactive bladder it is becoming clear that the control of bladder functioning is far more complex than previously believed. Peripherally, a prominent role has emerged for the urothelium and the underlying suburothelium in mechanosensory control, and the role of afferent pathways in pathophysiology is increasingly recognized.

SUMMARY

Recent research has highlighted several potential targets for treatment of the overactive bladder, particularly within the mechanosensory pathways. With the exception of botulinum toxin, however, few new therapies have emerged showing clinical benefits. A clearer understanding of the pathophysiology of the bladder will hopefully lead to more effective and tolerated treatments.

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

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

LUTS treatment: Future treatment options

Lower urinary tract symptoms (LUTS) are commonly divided into storage, voiding, and postmicturition symptoms, and may occur in both men and women. Male LUTS have historically been linked to benign prostatic hyperplasia (BPH), but are not necessarily prostate related. The focus of treatment for LUTS has thus shifted from the prostate to the bladder and other extraprostatic sites. LUTS include symptoms of the overactive bladder (OAB), which are often associated with detrusor overactivity. Treatment for LUTS suggestive of BPH has traditionally involved the use of alpha(1)-adrenoceptor (AR) antagonists; 5alpha-reductase inhibitors; and phytotherapy-however, several new therapeutic principles have shown promise. Selective beta(3)-adrenoceptor agonists and antimuscarinics are potentially useful agents for treating LUTS, particularly for storage symptoms secondary to outflow obstruction. Other agents of potential or actual importance are antagonists of P2X(3) receptors, botulinum toxin type A, endothelin (ET)-converting enzyme inhibitors, and drugs acting at vanilloid, angiotensin, and vitamin D(3) receptor sites. Drugs interfering with the nitric oxide/cGMP-cAMP pathway, Rho-kinase and COX inhibitors, as well as drugs targeting receptors and mechanisms within the CNS, are also of interest and deserving of further study for the treatment of LUTS.