The overactive bladder: pharmacologic basis of drug treatment

Adherence to Overactive Bladder Syndrome Treatments Recent Developments and Future Perspectives

Overactive bladder (OAB) is a common and distressing condition which is known to have a significant effect on Health-Related Quality of Life (HRQoL). Whilst all patients complaining of overactive bladder symptoms will, in theory, initially benefit from conservative measures, many will require pharmacological therapy. Antimuscarinics currently remain the most commonly used drugs to treat OAB although compliance and persistence can be poor due to concerns regarding adverse events and lack of efficacy. This review will explore the common management strategies for OAB with a particular focus on patient adherence to therapy including compliance and persistence. The role of antimuscarinics and the B3-agonist, mirabegron, will be considered along with barriers to their efficacy and adoption. For those patients in whom conservative and pharmacological treatment proves ineffective or is unsuitable, the management of refractory OAB will also be considered. In addition, the role of current and future developments will be examined.

The placebo and nocebo effects in functional urology

A placebo is an inert substance normally used in clinical trials for comparison with an active substance. However, a placebo has been shown to have an effect on its own; commonly known as the placebo effect. A placebo is an essential component in the design of conclusive clinical trials but has itself become the focus of intense research. The placebo effect is partly the result of positive expectations of the recipient on the state of health. Conversely, a nocebo effect is when negative expectations from a substance lead to poor treatment outcomes and/or adverse events. Randomized controlled trials in functional urology have demonstrated the importance of the placebo and nocebo effects across different diseases such as overactive bladder, urinary incontinence, lower urinary tract symptoms and interstitial cystitis/painful bladder syndrome, as well as male and female sexual dysfunction. Understanding the true nature of the placebo-nocebo complex and the scope of its effect in functional urology could help urologists to maximize the positive effects of this phenomenon while minimizing its potentially negative effects.

The cognitive safety of antimuscarinics in the treatment of overactive bladder

INTRODUCTION

Overactive bladder is a common problem women suffer from, with its incidence increasing with age. The mainstay of treatment is antimuscarinic medication. There is growing evidence that antimuscarinics may increase the risk of cognitive impairment, dementia, and even death.

AREAS COVERED

This review explores the evidence that antimuscarinics increase the risk of cognitive impairment, dementia, and death. It evaluates how best to treat overactive bladder the older woman.

EXPERT OPINION

The evidence suggests that antimuscarinics increase the risk of cognitive impairment and dementia in the older adult. Care should be taken to use an antimuscarinic that is less likely to cross the blood-brain barrier and thus reduce the risk of these significant adverse events. A patient's anticholinergic load also needs to be considered when treating this group. Other treatment options such as fluid management, bladder retraining, vaginal estrogens, mirabegron, Onabotulinum toxin A and neuromodulation can be used instead.

Managing overactive bladder

Overactive bladder (OAB) is a common and distressing condition which is known to increase with age and has a significant effect on quality of life. Whilst OAB is a symptomatic diagnosis, many patients will require basic investigations prior to initiating the appropriate management. This article will review the initial clinical assessment and management of women complaining of OAB including conservative measures and drug therapy, and will also focus on the role of estrogen. In addition, the management of refractory OAB will also be discussed including more invasive strategies such as neuromodulation, Botulinum Toxin, and reconstructive surgery.

Synthesis of substituted 7,7-dialkyl-5-chromanones and related compounds, new potassium channel activator

We describe the synthesis of 1-(6-hydroxy-4-methoxy-7,7-dimethyl-6,7-dihydro-5H-furo[3,2-g]chromen-5-yl) pyrrolidin-2-one (7) analogue to Cromakalim. Moreover, the synthesised furochromanone used to synthesise a fused heterocyclic compounds containing thiophene and coumarin rings via Gewald and Wittig reactions; respectively.

Evaluating the effect of three newly approved overactive bladder syndrome treating agents on parotid and submandibular salivary glands: Modulation of CXCL10 expression

BACKGROUND

Despite enormous progresses in understanding pathophysiology of the lower urinary tract, antimuscarinics remain the chief clinically well-established approach for improving symptoms of overactive bladder (OAB). Dry mouth on the other hand remains one of the most untolerated systemic side effects of these drugs that limits their uses and results in high discontinuation rate. Three novel drugs have been recently approved by US Food and Drug Administration for treatment of OAB: trospium, darifenacin, and solifenacin.

AIMS

This study has been conducted to provide clear head to head comparative studying of histological and ultrastructural effect of those newly emerging drugs on parotid and submandibular salivary glands and to demonstrate the differential expression of CXCL10 to make a cogent structural and molecular assessment of the relative tolerability of these drugs and the potential mechanisms of occurrence of dry mouth.

METHODS

Fifty male Sprague Dawley rats were equally divided into five groups: Group I (control), Group II (oxybutynin-treated), Group III (trospium-treated), Group IV (darifenacin-treated) and Group V (solifenacin-treated). Histological and ultrastructural studies were performed on parotid and submandibular glands. Measurement of salivary flow, PCR analysis and immunohistochemical assessment of CXCL10 expression have been carried-out.

RESULTS

Muscarinic receptor antagonists led to various histological, morphometric and ultrastructural changes together with diminished salivary secretion and up-regulation of CXCL10 expression with the mildest alterations observed with solifenacin.

CONCLUSIONS

Solifenacin has shown the least adverse effects to salivary glands. CXCL10 is involved in degenerative changes of salivary glands induced by muscarinic antagonists.

Pharmacotherapy for Pediatric Neurogenic Bladder

Neurogenic bladder (NB) is a nonspecific term that may describe conditions ranging from areflectic noncontractile bladder to detrusor overactivity. The most common cause of NB in children is the presence of dysraphic malformations. Urodynamic evaluations make it possible to describe bladder dysfunctions and to plan a therapeutic strategy for each patient. In a child with NB there are two major dangerous functional problems seen in urodynamic investigations: high intravesical pressure in the storage phase and high pressure during urination. The basic goals of urologic treatment for a child with NB are the protection of the urinary tract from complications and improvement of continence. Treatment for a child with NB is usually conservative, and focuses on achieving safe bladder pressures during storage with reliable emptying, via voiding or catheterization. The two most important forms of conservative treatment are clean intermittent catheterization and pharmacological treatment of functional disorders. Some drugs are used in the treatment of functional disorders in children with NB, but none of the drugs are officially approved for small children and babies.

Gentle Mechanical Skin Stimulation Inhibits Micturition Contractions via the Spinal Opioidergic System and by Decreasing Both Ascending and Descending Transmissions of the Micturition Reflex in the Spinal Cord

Recently, we found that gentle mechanical skin stimulation inhibits the micturition reflex in anesthetized rats. However, the central mechanisms underlying this inhibition have not been determined. This study aimed to clarify the central neural mechanisms underlying this inhibitory effect. In urethane-anesthetized rats, cutaneous stimuli were applied for 1 min to the skin of the perineum using an elastic polymer roller with a smooth, soft surface. Inhibition of rhythmic micturition contractions by perineal stimulation was abolished by naloxone, an antagonist of opioidergic receptors, administered into the intrathecal space of the lumbosacral spinal cord at doses of 2–20 μg but was not affected by the same doses of naloxone administered into the subarachnoid space of the cisterna magna. Next, we examined whether perineal rolling stimulation inhibited the descending and ascending limbs of the micturition reflex. Perineal rolling stimulation inhibited bladder contractions induced by electrical stimulation of the pontine micturition center (PMC) or the descending tract of the micturition reflex pathway. It also inhibited the bladder distension-induced increase in the blood flow of the dorsal cord at L5–S1, reflecting the neural activity of this area, as well as pelvic afferent-evoked field potentials in the dorsal commissure at the lumbosacral level; these areas contain long ascending neurons to the PMC. Neuronal activities in this center were also inhibited by the rolling stimulation. These results suggest that the perineal rolling stimulation activates the spinal opioidergic system and inhibits both ascending and descending transmissions of the micturition reflex pathway in the spinal cord. These inhibitions would lead to the shutting down of positive feedback between the bladder and the PMC, resulting in inhibition of the micturition reflex. Based on the central neural mechanisms we show here, gentle perineal stimulation may be applicable to several different types of overactive bladder.

Urinary Incontinence in the Young Woman: Treatment Plans and Options Available

Urinary incontinence is a common and distressing condition, which, although not life-threatening, is known to have a significant effect on quality of life. The incidence of urinary incontinence increases with age and while stress urinary incontinence is more common in younger women, symptoms suggestive of overactive bladder are more common with increasing age. All women complaining of incontinence require simple investigation, and many will benefit from conservative and medical treatments, which may be instituted in primary care. Further investigation in the secondary-care setting should be reserved for those women with refractory or unusual symptoms. The aim of this paper is to review the epidemiology and pathophysiology of common causes of urinary incontinence in younger, premenopausal women, and to review the current algorithms for investigation and management. In addition, treatment paradigms covering conservative, medical and surgical treatment for stress urinary incontinence and overactive bladder will be reviewed.

Pharmacotherapy of overactive bladder syndrome

Urinary incontinence is a common and distressing condition that is known to adversely affect quality of life. Overactive bladder (OAB) is the term used to describe the symptom complex of urgency with or without urge incontinence, usually with frequency and nocturia. Drug therapy, in addition to behavioral modification, remains integral in the management of women with OAB, and the development of new drugs, treatment regimens and methods of delivery should improve patient compliance and acceptability. Developments over the last 10 years have led to the launch of several new drugs for the treatment of OAB that may offer greater efficacy while minimizing adverse effects. This article critically reviews the current pharmacological treatment of OAB in addition to providing a rationale for treatment.

Fesoterodine fumarate and the oxybutynin ring for the treatment of urinary incontinence in women

INTRODUCTION

Urinary incontinence (UI) is a prevalent condition among women of all ages. It can have a significant negative impact on women's quality of life causing not only physical but also psychological distress.

AREAS COVERED

This article aims to provide a review of the pharmacology, efficacy, safety and tolerability of fesoterodine fumarate (the newest anticholinergic launched in the UK) and the oxybutynin vaginal ring (the newest route of drug delivery in development) in the treatment of urgency UI.

EXPERT OPINION

Fesoterodine is now a well-established treatment option; however, as with all oral anticholinergic agents its use is hindered by side effects. The efficacy of the oxybutynin ring has only been demonstrated in small studies. Larger clinical trials assessing the efficacy, tolerability and acceptability are required before appropriate recommendations can be made.

New developments in the medical management of overactive bladder

Overactive bladder (OAB) is a clinical syndrome describing the symptom complex of urgency, with or without urgency incontinence and is usually associated with frequency and nocturia. Whilst the majority of women will benefit from initial management with conservative and behavioural intervention a significant number will require medical therapy. Antimuscarinics are currently the most widely prescribed drugs for OAB although very often persistence with medication is limited due to lack of efficacy or intolerable adverse effects. The review, whilst giving a brief overview of OAB syndrome, will focus on new developments in drug therapy for OAB. In addition to evaluating new drugs with different methods of action it will also specifically focus on alternative modalities of treatment and how they may benefit patients with this troublesome and distressing condition.

Pathophysiology of overactive bladder

Overactive bladder (OAB) is a common disorder that negatively affects the quality of life of our patients and carries a large socioeconomic burden. According to the International Continence Society, it is characterized as urinary urgency, with or without urge incontinence, usually, with frequency and nocturia in the absence of causative infection. The pathophysiology of this disease entity varies between neurogenic, myogenic, or idiopathic factors. This paper provides a review of the contemporary theories behind the pathophysiology of OAB.

Overactive bladder: diagnosis and management

Overactive bladder (OAB) is a clinical syndrome describing the symptom complex of urgency, with or without urgency incontinence and is usually associated with frequency and nocturia. Whilst a number of women may be managed based on a clinical diagnosis alone urodynamic studies may be useful in those women with complex or refractory symptoms. In the first instance all women will benefit from a conservative approach using bladder retraining although a number will require antimuscarinic therapy. For those women with persistent symptoms following medical therapy alternative treatment modalities such as intravesical Botulinum Toxin, neuromodulation or reconstructive surgery may be considered. This review, whilst giving an overview of the syndrome, will focus on a practical clinical approach to managing women with symptoms of overactive bladder (OAB).

Tolerability of solifenacin and oxybutynin immediate release in older (> 65 years) and younger (≤ 65 years) patients with overactive bladder: sub-analysis from a Canadian, randomized, double-blind study

OBJECTIVE

Overactive bladder (OAB) is a common condition whose prevalence increases with age. Antimuscarinic agents are the pharmacologic treatment of choice, but adverse events such as dry mouth may lead to early discontinuation. The purpose of this analysis was to compare the incidence and severity of dry mouth and other adverse events with solifenacin 5 mg/day and oxybutynin immediate release (IR) 15 mg/day in patients ≤ 65 years and >65 years in the Canadian VECTOR study (VEsicare in Comparison To Oxybutynin for oveRactive bladder patients).

RESEARCH DESIGN AND METHODS

VECTOR was a randomized, multicentre, prospective, double-blind, double-dummy study in 132 subjects with ≥ 1 urgency episode per 24 h, with or without urgency incontinence, and ≥ 8 micturitions per 24 h for ≥ 3 months. After a 2-week washout, patients received solifenacin 5 mg once daily or oxybutynin IR 5 mg tid for 8 weeks. For the current post-hoc analysis, adverse events were evaluated in subgroups of patients ≤ 65 years and >65 years, using a full logistic regression model, multinomial logit regression model and reduced model.

CLINICAL TRIAL REGISTRATION

NCT00431041.

RESULTS

The incidence and severity of dry mouth and other adverse events with solifenacin were similar between younger and older patients. In both age subgroups, solifenacin 5 mg/day was associated with fewer episodes and lower severity of dry mouth, and a lower discontinuation rate, compared with oxybutynin IR 15 mg/day.

CONCLUSIONS

Solifenacin 5 mg/day was better tolerated than oxybutynin IR 15 mg/day in younger (≤ 65 years) and older (> 65 years) subgroups. Solifenacin was equally well tolerated in both age subgroups. Limitations of the analysis were that the study was not preplanned to perform post-hoc subgroup analysis, patients knew that dry mouth was a primary outcome, and the study used fixed doses of each drug.

AE9C90CB: a novel, bladder-selective muscarinic receptor antagonist for the treatment of overactive bladder

BACKGROUND AND PURPOSE

AE9C90CB (N- [(1R, 5S, 6R)-3-azabicyclo [3.1.0] hex-6-ylmethyl]-2-hydroxy-N-methyl-2, 2-diphenylacetamide), a novel muscarinic receptor antagonist, was synthesized for the treatment of overactive bladder. Here we describe the in vitro and in vivo profiles of AE9C90CB for action in bladder over salivary gland and compare it with four agents already in clinical use (tolterodine, oxybutynin, solifenacin and darifenacin).

EXPERIMENTAL APPROACH

Radioligand binding assay and isolated tissue-based functional assay were used to evaluate affinity, potency, and receptor subtype selectivity of compounds. Inhibition of carbachol-induced increase in intravesicular pressure and salivary secretion were measured in anaesthetized rabbits to assess the functional selectivity.

KEY RESULTS

In vitro radioligand binding study using human recombinant muscarinic receptors showed that AE9C90CB had greater affinity for M(3) muscarinic receptors with pKi of 9.90 +/- 0.11 and was 20-fold more selective for M(3) than for M(2) muscarinic receptors. AE9C90CB exhibited an unsurmountable antagonism on rat bladder strips (pK(B), 9.13 +/- 0.12). In anaesthetized rabbits after intravenous administration, AE9C90CB dose dependently inhibited carbachol-induced increase in intravesicular pressure and salivary secretion, and exhibited functional selectivity for urinary bladder over salivary gland which was ninefold better than that of oxybutynin.

CONCLUSIONS AND IMPLICATIONS

We have identified AE9C90CB, a compound exhibiting moderate selectivity for M(3) over M(2) receptors but greater selectivity for urinary bladder over salivary gland than oxybutynin, tolterodine, solifenacin and darifenacin. Therefore, AE9C90CB may be a promising compound for the treatment of overactive bladder with reduced potential to cause dry mouth than currently available antimuscarinic drugs.

New insights into molecular targets for urinary incontinence

Urinary incontinence (UI) is a disease affecting quality of life of 200 million patients worldwide. It is characterized by involuntary loss of urine. The factors involved are cystitis, detrusor hyperreflexia, spinal injury, benign prostatic hyperplasia, etc. The surge in the number of reviews on this subject indicates the amount of research devoted to this field. The prevalence is increasing at an alarming rate but unfortunately, only a few medications are currently available for this condition. There are peripheral as well as central targets including cholinergic, vanilloid, prostaglandin, kinin, calcium channel, cannabinoid, serotonin, and GABA-receptors, which act by different mechanisms to treat different types of incontinence. Drugs acting on the central nervous system (CNS) increase urinary bladder capacity, volume, or pressure threshold for micturition reflex activation while peripherally acting drugs decrease the amplitude of micturition contraction and residual volume. Anticholinergic drugs specifically M3 receptor antagonists are the first choice but have frequent side effects such as dry mouth, CNS disturbances, etc. Therefore, there is a need to understand the biochemical pathways that control urinary dysfunction to determine the potential to which they can be exploited in the treatment of this condition. This article reviews the central and peripheral molecular targets and the potential therapeutic approaches to the treatment of UI.

Behavioral intervention versus pharmacotherapy or their combinations in the management of overactive bladder dysfunction

Overactive bladder syndrome (OAB) refers to individuals with the following symptoms: urinary urgency, increased urinary frequency, and urge incontinence. These symptoms are not life threatening but can cause embarrassment and significantly impact quality of life. There are numerous treatment options for OAB, including behavioral therapy, traditional pharmacological therapy or a combination of the two. These options are considered the mainstay of treatment for OAB. We carried out a comprehensive systematic review of the available literature on the effectiveness of behavioral intervention, anticholinergic drugs, and their combination in the management of adults with overactive bladder, with emphasis on results from clinical trials and primary literature. Each treatment intervention is efficacious, and the choice should be based on the patient's severity of symptoms, tolerability, compliance and satisfaction with the treatment. Based on available literature, management of OAB using a combination of behavioral therapy and drug intervention is the most efficacious in terms of patient satisfaction, perceived improvement, and reduction of bladder symptoms. It is also the most practical and cost effective for optimal management of patients with OAB. Pharmacological treatment, in addition to behavioral therapy, remains important in the management of adults with OAB syndrome.

Neurokinins inhibit low threshold inactivating K+ currents in capsaicin responsive DRG neurons

Neurokinins (NK) released from terminals of dorsal root ganglion (DRG) neurons may control firing of these neurons by an autofeedback mechanism. In this study we used patch clamp recording techniques to determine if NKs alter excitability of rat L4-S3 DRG neurons by modulating K(+) currents. In capsaicin (CAPS)-responsive phasic neurons substance P (SP) lowered action potential (AP) threshold and increased the number of APs elicited by depolarizing current pulses. SP and a selective NK(2) agonist, [betaAla(8)]-neurokinin A (4-10) also inhibited low threshold inactivating K(+) currents isolated by blocking non-inactivating currents with a combination of high TEA, (-) verapamil and nifedipine. Currents recorded under these conditions were heteropodatoxin-sensitive (Kv4 blocker) and alpha-dendrotoxin-insensitive (Kv1.1 and Kv1.2 blocker). SP and NKA elicited a >10 mV positive shift of the voltage dependence of activation of the low threshold currents. This effect was absent in CAPS-unresponsive neurons. The effect of SP or NKA on K(+) currents in CAPS-responsive phasic neurons was fully reversed by an NK(2) receptor antagonist (MEN10376) but only partially reversed by a PKC inhibitor (bisindolylmaleimide). An NK(1) selective agonist ([Sar(9), Met(11)]-substance P) or direct activation of PKC with phorbol 12,13-dibutyrate, did not change firing in CAPS-responsive neurons, but did inhibit various types of K(+) currents that activated over a wide range of voltages. These data suggest that the excitability of CAPS-responsive phasic afferent neurons is increased by activation of NK(2) receptors and that this is due in part to inhibition and a positive voltage shift in the activation of heteropodatoxin-sensitive Kv4 channels.

Solifenacin: pharmacology and clinical efficacy

While antimuscarinic drug therapy has been proven to be effective in the management of patients with symptoms of overactive bladder syndrome, compliance and persistence with medication is often affected by the bothersome antimuscarinic adverse effects of dry mouth, constipation, somnolence and blurred vision. The development of bladder-selective M3-specific antagonists, such as solifenacin, has introduced the possibility of increasing efficacy while minimizing adverse effects. This article will review the preclinical and clinical data surrounding the development of solifenacin as well as providing an overview of the extensive body of evidence supporting its use in the management of patients with overactive bladder syndrome.

A randomized double-blind placebo-controlled multicentre study to explore the efficacy and safety of tamsulosin and tolterodine in women with overactive bladder syndrome

OBJECTIVES

To evaluate the efficacy of tamsulosin oral-controlled absorption system (OCAS) vs placebo in overactive bladder (OAB), to evaluate the safety and tolerability of once-daily dosing with tamsulosin OCAS, and to compare the efficacy and safety with tolterodine extended-release (ER).

PATIENTS AND METHODS

A parallel-group, multicentre, multinational study was conducted with a single-blind placebo run-in period of 2 weeks, followed by a randomized, double-blind, double-dummy active and placebo-controlled treatment period of 6 weeks; women (aged 18-70 years) with symptoms of OAB for >/= 3 months were recruited. Women were randomized to receive one of four doses of tamsulosin OCAS (0.25, 0.5, 1.0 or 1.5 mg), 4 mg of tolterodine ER, or placebo once daily for 6 weeks. The primary efficacy variable was the change in the mean number of voids/24 h. Secondary efficacy variables included change from baseline in; mean volume voided per void, mean number of incontinence episodes/24 h, mean number of urgency episodes/24 h and in quality of life (QoL), as assessed using the Kings Health Questionnaire (KHQ).

RESULTS

Overall, 364 women were randomized; the primary efficacy analysis showed that the difference from placebo in the mean number of voids/24 h was not statistically significant for tamsulosin OCAS 1.5 mg (P = 0.189). There was no statistically significant difference for tolterodine ER 4 mg vs placebo in the mean number of voids/24 h (P = 0.353). Similarly, for the secondary outcome variables there was no statistically significant difference between tamsulosin and placebo. Although women taking tolterodine ER 4 mg had a consistently greater increase in mean voided volume/void and consistent decreases in incontinence episodes/24 h, urgency episodes/24 h and episodes of nocturia/24 h, this was not statistically significant. There was no significant improvement in QoL scores across the treatment groups. Tamsulosin OCAS was well tolerated and the proportion of women discontinuing because of adverse events was low (4.7%).

CONCLUSION

Tamsulosin is not effective for treating OAB in women and the evidence from this study does not support its use on an empirical basis.

Management of overactive bladder syndrome

Overactive bladder (OAB) syndrome is the term used to describe the symptom complex of urinary urgency with or without urge incontinence, usually with frequency and nocturia. Drug treatment continues to have an important role in the management of women with OAB. Other treatment options include conservative management with lifestyle interventions, modification of fluid intake, and physiotherapy including bladder retraining. Surgery remains the last resort in the treatment and is usually reserved for intractable detrusor overactivity, as it is associated with significant morbidity. This article reviews the management of the overactive bladder with specific focus on newer developments in the medical treatment of OAB in women.

Inhibitory effects of aqueous extract of Hibiscus sabdariffa on contractility of the rat bladder and uterus

We examined an aqueous extract of Hibiscus sabdariffa calyces extracts (HSE) by close-arterial injection on micturition thresholds (MTs) and on uterine contractions (rate and amplitude). Five doses of HSE were examined (1, 5, 10, 50, and 100 mg/kg) in 3 groups of rats: controls, after bladder inflammation, and after bilateral hypogastric neurectomy. In some rats, uterine contractions were induced by injection of oxytocin (OT) and the effect of HSE was compared with that of nifedipine. HSE increased MTs in a dose-dependent manner in all groups. Neither atropine (0.1 mg/kg) nor propranolol (0.4 mg/kg) had significant effects on cystometric parameters. They also did not affect the responses obtained by HSE on cystometric parameters. As with bladder response, HSE inhibited both the rate and amplitude of uterine contractions in all groups in a dose-dependent manner. The uterine response to HSE was not affected by administration of either atropine or propranolol. A slight, but significant, reduction of contraction amplitude by HSE in the OT precontracted uteri was only noted at a dose of 500 mg/kg. Nifedipine was more potent than HSE in reducing uterine contraction amplitude. The present work documents inhibition by HSE of the rat bladder and uterine contractility in a dose-dependent manner via a mechanism unrelated to local or remote autonomic receptors or calcium channels. However, further investigation is needed to establish the exact mechanism of action.

Neurokinins enhance excitability in capsaicin-responsive DRG neurons

Neurokinins released by capsaicin-responsive (C-R) dorsal root ganglia neurons (DRG) may control firing in these neurons by an autofeedback mechanism. Here we used patch clamp techniques to examine the effects of neurokinins on firing properties of dissociated DRG neurons of male rats. In C-R neurons that generated only a few action potentials (APs, termed phasic) in response to long depolarizing current pulses (600 ms), substance P (SP, 0.5 microM) lowered the AP threshold by 11.0+/-0.3 mV and increased firing from 1.1+/-0.7 APs to 5.2+/-0.6 APs. In C-R tonic neurons that fire multiple APs, SP elicited smaller changes in AP threshold (6.0+/-0.1 mV reduction) and the number of APs (11+/-1 vs. 9+/-1 in control). The effects of SP were similar to the effect of heteropodatoxin II (0.05 microM) or low concentrations of 4-aminopyridine (50 microM) that block A-type K(+) currents. A selective NK(2) agonist, [betaAla(8)]-neurokinin A (4-10) (0.5 microM), mimicked the effects of SP. The effects of SP in C-R phasic neurons were fully reversed by an NK(2) receptor antagonist (MEN10376, 0.5 microM) but only partially by a protein kinase C (PKC) inhibitor (bisindolylmaleimide, 0.5 microM). An NK(3)-selective agonist ([MePhe(7)]-neurokinin B, 0.5 microM), an NK(1)-selective agonist ([Sar(9), Met(11)]-substance P, 0.5 microM) or activation of PKC with phorbol 12,13-dibutyrate (0.5 microM) did not change firing. Our data suggest that the excitability of C-R phasic afferent neurons is increased by activation of NK(2) receptors and intracellular signaling mediated only in part by PKC.

Tolterodine for Treatment of Overactive Bladder

Tolterodine was developed as an antimuscarinic agent specifically for the treatment of overactive bladder. Initial in vivo studies demonstrated a functional selectivity for the muscarinic receptors in the urinary bladder over the salivary glands, and subsequent clinical trials showed an overall superior tolerability profile compared with other drugs in the same class (ie, oxybutynin). With immediate- and extended-release formulations and sustained clinical efficacy during long-term treatment, tolterodine gas become an important treatment option for the symptoms of overactive bladder.

The clinical pharmacokinetics of darifenacin

Darifenacin hydrobromide is a selective muscarinic M(3) receptor antagonist that is indicated for use in treatment of overactive bladder disorder. Darifenacin was found to have a short terminal elimination half-life after intravenous and immediate-release oral dosage forms (3-4 hours) but this increased with a prolonged-release (PR) formulation (14-16 hours). The absolute bioavailability of darifenacin from 7.5 and 15 mg PR tablets was estimated to be 15.4% and 18.6%, respectively. With repeated once-daily oral administration of the PR formulation, peak plasma concentrations of darifenacin are achieved approximately 7 hours post-dose. After oral administration, darifenacin is well absorbed from the gastrointestinal tract and very little unchanged drug (<2%) is recovered in the faeces. Steady state is achieved after 6 days of once-daily administration of the PR formulation. As expected, values of peak plasma concentration (C(max)) and area under the plasma concentration-time curve are dose dependent, although the increase in plasma concentrations is proportionally greater than the increase in dose owing to saturation of presystemic metabolism. From intravenous administration, it has been established that darifenacin possesses a moderate-to-high hepatic extraction ratio, with high plasma clearance (36-52 L/h) and a volume of distribution (165-276L) that exceeds total body water. It is highly protein bound (98%), primarily to alpha(1)-acid glycoprotein. Darifenacin is subject to extensive hepatic metabolism, with 3% of unchanged drug excreted in urine and faeces. Metabolism is mediated by hepatic cytochrome P450 2D6 and 3A4, the main metabolic routes being monohydroxylation in the dihydrobenzfuran ring, dihydrobenzfuran ring opening, and N-dealkylation of the pyrrolidine nitrogen. Several possibly important drug-drug interactions have been identified with darifenacin, including ketoconazole, erythromycin and fluconazole, each of which increases darifenacin mean C(max) by 9.52-, 2.28- and 1.88-fold, respectively. When given with imipramine, darifenacin causes 1.6-fold higher plasma concentrations of the antidepressant and its major metabolite. Moderate hepatic impairment, but not renal insufficiency, has been shown to increase plasma concentrations of the drug. The pharmacokinetic profile of darifenacin is not affected by food.

Contractile mechanisms coupled to TRPA1 receptor activation in rat urinary bladder

TRPA1 is a member of the transient receptor potential (TRP) channel family present in sensory neurons. Here we show that vanilloid receptor (TRPV1) stimulation with capsaicin and activation of TRPA1 with allyl isothiocyanate or cinnamaldehyde cause a graded contraction of the rat urinary bladder in vitro. Repeated applications of maximal concentrations of the agonists produce desensitization to their contractile effects. Moreover, contraction caused by TRPA1 agonists generates cross-desensitization with capsaicin. The TRP receptor antagonist ruthenium red (10-100 microM) inhibits capsaicin (0.03 microM), allyl isothiocyanate (100 microM) and cinnamaldehyde (300 microM)-induced contractions in the rat urinary bladder. The selective TRPV1 receptor antagonist SB 366791 (10 microM) blocks capsaicin-induced contraction, but partially reduces allyl isothiocyanate- or cinnamaldehyde-mediated contraction. However, allyl isothiocyanate and cinnamaldehyde (10-1000 microM) completely fail to interfere with the specific binding sites for the TRPV1 agonist [(3)H]-resiniferatoxin. Allyl isothiocyanate or cinnamaldehyde-mediated contractions of rat urinary bladder, which rely on external Ca(2+) influx, are significantly inhibited by tachykinin receptor antagonists as well as by tetrodotoxin (1 microM) or indomethacin (1 microM). Allyl isothiocyanate-induced contraction is not changed by atropine (1 microM) or suramin (300 microM). The exposure of urinary bladders to allyl isothiocyanate (100 microM) causes an increase in the prostaglandin E(2) and substance P levels. Taken together, these results indicate that TRPA1 agonists contract rat urinary bladder through sensory fibre stimulation, depending on extracellular Ca(2+) influx and release of tachykinins and cyclooxygenase metabolites, probably prostaglandin E(2). Thus, TRPA1 appears to exert an important role in urinary bladder function.

The Causes and Consequences of Overactive Bladder

Overactive bladder (OAB) is a syndrome characterized by symptoms of urinary urgency with or without urgency urinary incontinence (UUI), usually with frequency and nocturia. OAB affects approximately 17% of women in the United States and Europe. The causes of OAB, as with many bladder disorders, are multifactorial and are not completely understood. The primary functions of the lower urinary tract (bladder and bladder outlet mechanism) are storage and evacuation of urine. The bladder and the micturition cycle are under complex neural control involving both the sympathetic and parasympathetic nervous systems. Micturition may occur in response to the activation of receptors in the bladder muscle and detection of chemical stimuli by receptors within the bladder lining. Neurogenic or myogenic bladder dysfunction can lead to the symptoms of urgency, frequency, and UUI that characterize OAB. The consequences of this condition are far-reaching and include direct medical consequences and coping strategies that adversely affect quality of life. Although the prevalence of OAB increases with age, it is not a normal consequence of aging. Antimuscarinic agents (e.g., oxybutynin, tolterodine, trospium, solifenacin, and darifenacin) have demonstrated efficacy for the treatment of OAB symptoms in multiple clinical trials. This review explores the physiological basis for OAB, the effects of OAB on health-related quality of life, and the pharmacotherapies that may provide relief to patients with this distressing condition.

Pharmacological treatment for overactive bladder in women

Urinary incontinence is a common and distressing condition that is known to adversely affect quality of life. Overactive bladder is the term used to describe the symptom complex of urinary frequency and urgency, with or without urge incontinence. Drug therapy, in addition to behavioral modification, remains integral in the management of women with overactive bladder, and the development of new drugs, treatment regimens and methods of delivery should improve patient compliance and acceptability. This article critically reviews the current pharmacological treatment of overactive bladder in addition to providing a rationale for treatment.

Antimuscarinic drugs for the treatment of female urinary incontinence

Overactive bladder syndrome, urge syndrome or urgency-frequency syndrome is defined as 'urgency with or without urge incontinence, usually with frequency and nocturia'. Although this definition indicates that these symptoms are suggestive of detrusor overactivity (the observation of involuntary detrusor contractions during the filling phase of cystometry), a urodynamic demonstration of detrusor overactivity is not necessary in order to make the diagnosis. Nevertheless, patients with overactive bladder syndrome represent a substantial proportion of patients suffering with urinary symptomatology, and approximately a third of individuals with overactive bladder suffer from incontinence. Furthermore, as compared with those patients with stress urinary incontinence, women with urge incontinence have a poorer overall quality of life, perhaps related to both the volume of urine lost as well as the unpredictable nature of the leakage. When combined with behavioral modification, antimuscarinic pharmacotherapy remains the mainstay of treatment for this condition. A number of these agents are available for the treatment of overactive bladder-related incontinence, each with unique pharmacokinetic and pharmacodynamic properties. In order to optimize therapy for patients suffering from this type of incontinence, it is necessary to understand the mechanism of action of these agents, as well as to be familiar with the differences between them with respect to efficacy, safety and tolerability.

Solifenacin in the management of the overactive bladder syndrome

Overactive bladder (OAB) is the term used to describe the symptom complex of urinary frequency and urgency, with or without urge incontinence. Whilst antimuscarinic drug therapy has proven to be effective in the management of patients with symptoms of the OAB syndrome, compliance with medication is often affected by the bothersome antimuscarinic adverse effects of dry mouth, constipation, somulence and blurred vision. The development of bladder selective M3 specific antagonists offers the possibility of increasing efficacy whilst minimising adverse effects. At present, there are no M3 specific antagonists currently available, although solifenacin and darifenacin are under development and are due to be registered in 2004-2005. The purpose of this article is to review the pharmacology and clinical trial data available for solifenacin in addition to examining its emerging role in the treatment of the OAB syndrome.

Regional differences in responses of rabbit detrusor to electrical and adrenergic stimulation: influence of outlet obstruction

OBJECTIVE

To examine regional responses of control and obstructed rabbit detrusor strips to electrical and adrenergic stimulation, and determine whether outlet obstruction causes regional variations in blood flow throughout the detrusor, as the detrusor smooth muscle of the bladder body has previously been considered homogeneous in its pharmacological properties.

MATERIALS AND METHODS

Fourteen male rabbits had the bladder outlet surgically obstructed for 2 weeks and were compared with 10 unoperated control rabbits. Blood flow was measured with the bladder empty and at capacity, using fluorescent microspheres. Paired dorsal and ventral strips were harvested from the midline equatorial detrusor and electrically and adrenergically stimulated.

RESULTS

Obstructed rabbits had significantly higher bladder capacities and bladder weights than control rabbits. Dorsal strips from both control and obstructed rabbits contracted in response to noradrenaline, whereas ventral strips relaxed. The addition of prazosin, a nonselective alpha1-adrenergic-receptor blocker, completely blocked the contraction in dorsal strips, but had no effect on responses of ventral strips. There was also a regional difference in response to electrical stimulation, with ventral strips generating significantly more tension than dorsal strips in both control and obstructed rabbits. There were no regional differences in detrusor blood flow. Obstruction resulted in significantly lower responses to all forms of stimulation, and significantly less blood flow throughout the detrusor.

CONCLUSION

There are regional differences in adrenergic receptor function and response to electrical-field stimulation throughout control and obstructed rabbit detrusor, a region that was previously thought to be functionally homogeneous. These differences must be recognized and acknowledged to obtain accurate and reproducible data from in vitro studies of the bladder.

Gene therapy treatments for erectile and bladder dysfunction

The postgenomic age presents many exciting challenges and opportunities for the application of molecular medicine to the treatment of lower urinary tract diseases. Chief among these are the therapeutic possibilities afforded to selectively modulate/alter gene expression in somatic cells to "normalize" aberrant cellular responses to the existing hormonal milieu. In this paper, this therapeutic strategy will be referred to as gene therapy or gene transfer. This article specifically reviews the potential use of gene therapy/transfer to the treatment of bladder and erectile dysfunction. Available treatments for both of these common urologic diseases/disorders have contraindications, untoward side effects, or limited efficacy in certain patient populations. Moreover, that genetic material can be locally administered in the bladder and penis removes a major therapeutic obstacle to the use of gene transfer. Thus far, "proof-of-concept" has been demonstrated in preclinical studies using cellular and molecular strategies on a variety of gene targets. The continuing evolution of gene transfer vectors and gene delivery technologies is expected to further enhance the selectivity, efficacy, and duration of gene therapy, making it a viable treatment option for the amelioration of lower urinary tract diseases/disorders.