Antimuscarinics and the overactive detrusor--which is the main mechanism of action?

Oxybutynin gel for the treatment of overactive bladder

INTRODUCTION

Overactive bladder (OAB) is a common condition that has a profound impact on an individual's overall health and quality of life. Muscarinic receptor antagonists are the mainstay of oral pharmacotherapy for OAB. While all of the medications in this class are significantly more effective than placebo, they are also associated with more adverse events that may limit their overall use. Transdermal application of oxybutynin has been shown to avoid first-pass metabolism and, thus, may be associated with fewer antimuscarinic side effects.

AREAS COVERED

This paper reviews the pharmacology of transdermal oxybutynin gel and summarizes the available data regarding this product in the treatment of OAB. It also discusses the role of this product in the OAB treatment armamentarium.

EXPERT OPINION

Oxybutynin transdermal gel has been shown to have significant advantages over placebo, in terms of urgency incontinence episodes, urinary frequency and voided volume in a Phase III study. Application site effects were higher in the gel group, but the incidence of antimuscarinic side effects were lower than those seen with oral preparations. The lower incidence of skin side effects, as compared with the transdermal patch, may confer a theoretical advantage toward the gel product. While promising, unanswered questions remain regarding persistence with treatment after this mode of therapy, and head-to-head comparisons with other antimuscarinics are absent.

Muscarinic agonists and antagonists: effects on the urinary bladder

Voiding of the bladder is the result of a parasympathetic muscarinic receptor activation of the detrusor smooth muscle. However, the maintenance of continence and a normal bladder micturition cycle involves a complex interaction of cholinergic, adrenergic, nitrergic and peptidergic systems that is currently little understood. The cholinergic component of bladder control involves two systems, acetylcholine (ACh) released from parasympathetic nerves and ACh from non-neuronal cells within the urothelium. The actions of ACh on the bladder depend on the presence of muscarinic receptors that are located on the detrusor smooth muscle, where they cause direct (M₃) and indirect (M₂) contraction; pre-junctional nerve terminals where they increase (M₁) or decrease (M₄) the release of ACh and noradrenaline (NA); sensory nerves where they influence afferent nerve activity; umbrella cells in the urothelium where they stimulate the release of ATP and NO; suburothelial interstitial cells with unknown function; and finally, other unidentified sites in the urothelium from where prostaglandins and inhibitory/relaxatory factors are released. Thus, the actions of muscarinic receptor agonists and antagonists on the bladder may be very complex even when considering only local muscarinic actions. Clinically, muscarinic antagonists remain the mainstay of treatment for the overactive bladder (OAB), while muscarinic agonists have been used to treat hypoactive bladder. The antagonists are effective in treating OAB, but their precise mechanisms and sites of action (detrusor, urothelium, and nerves) have yet to be established. Potentially more selective agents may be developed when the cholinergic systems within the bladder are more fully understood.

Inhibition of stretching-evoked ATP release from bladder mucosa by anticholinergic agents

OBJECTIVE

To determine whether muscarinic receptor antagonism affects stretching-induced release of ATP.

MATERIALS AND METHODS

Mucosal strips, dissected from guinea pig (male, 450g; n = 10) urinary bladders, were placed in horizontal organ baths and superfused with Ca(2+) -free Tyrode's solution. Superfusate samples were taken pre- and post- intervention (rapid stretching or relaxation) and ATP concentration was quantified using a luciferin-luciferase assay. The effect of muscarinic acetylcholine receptor antagonism on ATP release was assessed by addition of methoctramine (1 µM) and 4-DAMP (10 nM).

RESULTS

Rapid stretching (0 to 13.3 ± 1.2 mN; no. strips = 20) increased ATP in the superfusate to a median threefold increase over basal levels. After a period of equilibration, tension in the mucosal strips relaxed until it had reached a new steady-state after 60 min and stretching was repeated. In the presence of 4-DAMP (10 nM) or methoctramine (1 µM), ATP concentrations after stretching reduced to 61% or 20%, respectively. By contrast, ATP concentrations in mucosa-matched controls, perfused with vehicle, increased in response to stretching by 391% and 1500%, respectively. Rapid relaxation also stimulated ATP release. This release did not appear to be sensitive to 4-DAMP or methoctramine.

CONCLUSIONS

An alteration of resting mucosal tension is the key determinant of ATP release, as ATP is released from the mucosa in response to both stretching and relaxation. Muscarinic receptor antagonism inhibits stretching-evoked ATP release from bladder mucosa, suggesting that anticholinergic agents used to treat human lower urinary tract pathologies act on urothelial muscarinic receptors.

Antimuscarinic drugs: review of the cognitive impact when used to treat overactive bladder in elderly patients

The blockade of muscarinic receptors in the management of overactive bladder (OAB) symptoms provides beneficial as well as adverse effects. The cognitive changes observed are caused by the drugs' ability to cross the blood-brain barrier and bind to muscarinic receptors within the central nervous system (CNS). To date, while not specifically testing for CNS side effects, most of the controlled efficacy trials of multiple OAB medications have not shown significant adverse effects on cognitive function. However, elderly individuals, in whom OAB is more prevalent, often are excluded from these studies. The few trials that have performed cognitive testing in healthy elderly people taking antimuscarinics have clearly shown that oxybutynin can adversely affect cognition. Darifenacin, trospium, solifenacin, and tolterodine appear to have little to no risk of causing CNS side effects in this population. However, caution needs to be used in elderly patients with preexisting dementia.

Antimuscarinic effects on current perception threshold: a prospective placebo control study

AIMS

To evaluate the effect of Tolterodine on urethral and bladder afferent nerves in women with detrusor overactivity (DO) in comparison to placebo, by studying the changes in the current perception threshold (CPT).

METHODS

Women with overactive bladder symptoms and idiopathic DO were recruited and randomized in a double-blind manner between placebo and tolterodine extended release. All women underwent CPT testing of the bladder and urethra using a Neurometer constant current stimulator. CPT values were determined at three frequencies, including 2,000 Hz (corresponding to Aβ-fibers), 250 Hz (corresponding to Aδ-fibers), and 5 Hz (corresponding to C fibers) before and 7 days on treatment. CPT values before and on treatment were compared using a Wilcoxon Signed Rank test.

RESULTS

Twenty women (mean age 46 years) were studied. There was no statistical difference between the two groups in terms of age, ethnicity, severity of symptoms and pre-treatment CPT values. Only in the tolterodine group there was a significantly increased CPT value at 5 and 250 Hz upon both urethral and bladder stimulation after 1 week of treatment. When compared with placebo, women taking tolterodine had significantly increased Bladder CPT values at 5 Hz (P-value <0.05). The electrical stimulation with 5 Hz was described as urgency.

CONCLUSIONS

This is a randomized placebo control study evaluating the effect of antimuscarinics on sensory nerve function in women with DO. Our results support the animal studies that antimuscarinics have an effect on sensory function.

Dissimilar effects of tolterodine on detrusor overactivity in awake rats with chemical cystitis and partial bladder outlet obstruction

Purpose

We investigated bladder function, with a special focus on nonvoiding contractions (NVCs), in awake rats with chronic chemical cystitis and bladder outlet obstruction (BOO) by use of simultaneous registrations of intravesical and intraabdominal pressures. In addition, we tested the effects of tolterodine on the NVCs in these models.

Methods

A total of 20 female Sprague-Dawley rats were used in this study. In eight rats, chemical cystitis was induced by intravesical instillation of HCl. Twelve rats were subjected to sham instillations or partial BOO. Four weeks after intravesical instillation or 2 weeks after partial BOO, cystometrograms were obtained by use of simultaneous recording of intravesical and intraabdominal pressure in all unanesthetized, unrestrained rats in metabolic cages.

Results

A total of 17 rats survived. In the rats with acute injury by HCl, 50% showed detrusor overactivity (DO), which was not seen in the sham group. The cystitis group had lower DO pressure without a difference in DO frequency compared with the BOO group. After the administration of tolterodine, the cystitis group showed no difference in DO frequency or pressure, whereas the BOO group showed decreased values for both parameters.

Conclusions

Our study showed that toleterodine produced no effect on DO during the filling phase in rats with chronic chemical cystitisbut decreased the frequency and pressure of DO in rats with BOO. Clinically, studies are needed to improve the treatment effect of anticholinergic drugs ininterstitial cystitis patients with overactive bladder.

In vivo bladder selectivity of imidafenacin, a novel antimuscarinic agent, assessed by using an effectiveness index for bladder capacity in rats

Imidafenacin (KRP-197) is a novel antimuscarinic agent for overactive bladder treatment. The inhibitory effect of imidafenacin on detrusor contraction has been adopted for assessing their bladder selectivity, but this is becoming less convincing as an effectiveness index. We, therefore, reevaluated the bladder selectivity of imidafenacin and other antimuscarinics using their effects on the bladder capacity as an effectiveness index. Bladder capacity was measured by intermittent cystometry in urethane-anesthetized rats. In the tissues related to antimuscarinic side effects, the inhibitory actions were measured each on salivary secretion by electrical stimulation of chorda tympani, on rhythmical contractions in colon, and on carbamylcholine-induced bradycardia. Imidafenacin, solifenacin succinate, tolterodine tartrate, and propiverine hydrochloride significantly increased the bladder capacity, with minimum effective doses of 0.003, 1, 0.03, and 3 mg/kg (i.v.), respectively. The antimuscarinics tested, except for propiverine hydrochloride, shared a common property of increasing bladder capacity at a dose which did not affect micturition pressure. The relative bladder selectivity of imidafenacin, solifenacin succinate, and tolterodine tartrate was 15-, 1.7-, and 2.5-fold higher over salivary gland; 150-, 1.9-, and 9.2-fold higher over colon; and 50-, 12-, and 4.6-fold higher over heart, respectively, than that of propiverine hydrochloride. Thus, imidafenacin shows the most highly selective for bladder over the tissues related to major antimuscarinic side effects, compared to the other three well-known antimuscarinics tested in the rat.

Distribution of interstitial cells of Cajal and expression of nitric oxide synthase after experimental bladder outlet obstruction in a rat model of bladder overactivity

AIMS

Recent studies have showed that interstitial cells (ICs) are widely distributed in the genitourinary tract and have suggested their involvement in spontaneous electrical activity and muscle contraction. Nitric oxide (NO) is thought to play a role in bladder overactivity related with bladder outlet obstruction (BOO). The purposes of this study were to investigate the effect of bladder overactivity induced by BOO on ICs and nitric oxide synthase (NOS) isoforms in rat urinary bladder.

METHODS

Female Sprague-Dawley rats (230-240  g, n = 40) were divided into two groups: control (group Con, n = 20) and partial BOO (group BOO, n = 20). After 4 weeks, urodynamic studies measuring contraction interval and contraction pressure were done. The cellular localization of cKit immunoreactive ICs and the expression of endothelial NOS (eNOS) and neuronal NOS (nNOS) were determined by Western blot and immunohistochemistry in the rat urinary bladder.

RESULTS

Filling cystometry studies demonstrated a reduced interval between voiding contractions and an increased voiding pressure in BOO bladders. The contraction interval time (2.9 ± 0.35  min) was significantly decreased in the BOO group compared to the control (6.1 ± 0.05; P < 0.05). The population of ICs was increased in the suburothelial and muscle layers in BOO bladders. ICs had a close contact with each other and neighboring nNOS expressing cells.

CONCLUSIONS

These results demonstrated an increased population of ICs in the BOO rat model and suggest that the functional change of ICs and NOS isoforms may contribute to the pathophysiology of bladder overactivity induced by BOO.

Antimuscarinics suppress adenosine triphosphate and prostaglandin E2 release from urothelium with potential improvement in detrusor overactivity in rats with cerebral infarction

PURPOSE

Antimuscarinics improve detrusor overactivity. We evaluated the effects and action mechanisms of imidafenacin (Kyorin Pharmaceutical, Tokyo, Japan), a novel therapeutic agent for overactive bladder with antimuscarinic activity, on mediator release from urothelium and detrusor overactivity induced by cerebral infarction.

MATERIALS AND METHODS

Bladder hydrodistention was achieved by intravesical infusion of Krebs solution. Bladder adenosine triphosphate and prostaglandin E(2) were measured in the presence and absence of anticholinergics using luciferin-luciferase assay and enzyme-linked immunoassay, respectively. Cerebral infarction was induced in rats by occluding the left middle cerebral artery. The effects of intravenous imidafenacin on bladder function were examined using cystometry in rats with cerebral infarction and in those pretreated with resiniferatoxin.

RESULTS

Increased intravesical adenosine triphosphate and prostaglandin E(2) were shown by induced distention of isolated rat bladders. Imidafenacin and darifenacin (Kemprotec, Middlesbrough, United Kingdom) significantly suppressed the increases in adenosine triphosphate and prostaglandin E(2). Decreased bladder capacity was observed in rats with cerebral infarction. Detrusor overactivity was suppressed with a minimum intravenous dose of 0.001 mg/kg imidafenacin. The effects of imidafenacin were not noted in rats pretreated with resiniferatoxin.

CONCLUSIONS

Results support the hypothesis or suggest that imidafenacin improves cerebral infarction induced detrusor overactivity by suppressing peripheral C-fibers. This effect is thought to be associated with suppression of the release of adenosine triphosphate and prostaglandin E(2) from the urothelium.

Comparisons of urodynamic effects, therapeutic efficacy and safety of solifenacin versus tolterodine for female overactive bladder syndrome

AIM

To evaluate the urodynamic effects, therapeutic efficacy and safety of solifenacin versus tolterodine treatment for women with overactive bladder syndrome.

METHODS

Patients were randomized to receive either solifenacin 5 mg or tolterodine ER 4 mg once a day for 12 weeks at each four-week visit in a post-marketing study. Only women (solifenacin [n = 26] vs. tolterodine [n = 22]) were included in this subgroup analysis. Adverse events and changes of urodynamic values and clinical data were compared between the solifenacin and tolterodine groups.

RESULTS

The volume voided per micturition increased in the solifenacin group (n = 21) (P = 0.04). The strong desire to void and pad-test result improved in the tolterodine group (n = 21; P = 0.02 and 0.03, respectively). There were no between-group differences in changes of any urodynamic data, voiding diary values or adverse events after treatment; however, changes of heart rate differed between the two groups (P = 0.0004), especially at visit 2 (solifenacin vs. tolterodine, -4.3 vs. 3.8, P = 0.02) and visit 3 (-3.2 vs. 4.8, P = 0.03).

CONCLUSIONS

Both solifenacin and tolterodine had similar urodynamic effects, therapeutic efficacy and adverse events in treating women with overactive bladder syndrome; however, tolterodine had a greater effect in increasing heart rate than solifenacin.

The role of antimuscarinics in the management of men with symptoms of overactive bladder associated with concomitant bladder outlet obstruction: an update

CONTEXT

This review focuses on the contemporary role of antimuscarinics in the management of men with symptoms of bladder outlet obstruction (BOO) and concomitant overactive bladder (OAB). Safety issues of antimuscarinics in this subpopulation of men are also reviewed.

OBJECTIVE

We reviewed the current literature and performed an analysis of the efficacy, suitability, and the safety of antimuscarinics in this subpopulation of men.

EVIDENCE ACQUISITION

We performed a systematic search of Medline/PubMed, Embase, Scopus, and the Cochrane Database of Systematic Reviews for relevant articles published between 1990 and September 2010, restricted to studies in humans published in English. In addition, published abstracts presented at the annual meetings of the European Association of Urology, the American Urological Association, and the International Continence Society in the last decade (2000-2010) were hand-searched and evaluated. Each article's title and abstract were reviewed for their appropriateness and relevance to the use of antimuscarinics in patients with BOO and concomitant OAB. Relevant articles were fully reviewed and included in the final data acquisition.

EVIDENCE SYNTHESIS

Treatment options include combination treatment with α-blockers and antimuscarinics, sequential use of α-blockers and antimuscarinics, monotherapy with antimuscarinics, and a combination of antimuscarinics and 5α-reductase inhibitors. The sequential use of α-blockers and antimuscarinics seems to be the most appropriate approach, and the use of antimuscarinics and α-blockers appears generally to be safe and efficacious. Data are insufficient for a possible stratification of patients for a specific sequence of the drugs reviewed.

CONCLUSIONS

This review infers that the existing data confirm the safety of antimuscarinics administered for the treatment of these patients. The efficacy of antimuscarinics has been proven in different trials regarding different storage symptom end points, but not all end points regarding OAB reached significance. All the reported trials are of short duration (4-12 wk) and include only men with low postvoid residual urine volumes at baseline (<200ml). Overall, the addition of an antimuscarinic to the treatment of a patient with BOO and concomitant OAB seems to offer an amelioration of the symptoms and a moderate improvement in quality of life.

Comparative analysis of the effects of antimuscarinic agents on bladder functions in both nonhuman primates and rodents

Both the physiological role of muscarinic receptors for bladder function and the therapeutic efficacy of antimuscarinic agents for overactive bladder syndrome are well documented. We investigated the effect of antimuscarinic agents with different subtype selectivity on urodynamic parameters in nonhuman primates and rodents and compared plasma levels of these agents between species. Anesthetized rhesus monkeys were transurethrally catheterized, and the bladder was infused with saline. Urodynamic parameters were measured before and after intravenous drug administration. Tolterodine (nonselective) and oxybutynin (moderately M(3)-selective) increased bladder capacity at lower doses than those required to decrease micturition pressure. However, higher doses of darifenacin (M(3)-selective) were needed to increase the bladder capacity than those needed to decrease the micturition pressure. In rats, tolterodine had no effect on the bladder capacity but decreased the micturition pressure at all of the doses administered. Oxybutynin also decreased micturition pressure and increased bladder capacity at the highest dose. Plasma levels of these drugs overlap in both species. These results suggest that, in addition to the M(3) receptor, other muscarinic receptor subtypes contribute to regulate bladder storage function in nonhuman primates, since less subtype-selective tolterodine and oxybutynin showed higher specificity to the bladder capacity effect than the effect on micturition pressure compared with M(3)-selective darifenacin. In addition, the role of muscarinic receptors in bladder storage function varies between primates and rodents. Compared with rodents, muscarinic receptors may play a more active role during the storage phase to regulate the functional bladder capacity in primates.

Urological Disorders in Men

Urinary incontinence (UI) and benign prostatic hyperplasia (BPH) are 2 common urogenital problems in men. UI is associated with involuntary leakage of urine and lower urinary tract symptoms (LUTS) of urgency, frequency, and nocturia. Types of UI include functional, urge, stress, and overflow. Treatment for UI is based on the type of incontinence, patient-specific factors, and treatment preferences of both patients and health care providers. Options for the management of UI include environmental modifications, disposable incontinence products, pelvic floor exercises, pharmacotherapy, surgically implanted devices, and intermittent catheterization. BPH may be also associated with LUTS. Patient symptoms, assessed with a measurement tool such as the American Urological Association Symptom Index (AUASI), serve as the basis for determining treatment. Management approaches for BPH include pharmacotherapy, surgery, and minimally invasive procedures. Anticholinergic drugs as well as α-receptor antagonists and 5-α reductase inhibitors, either alone or in combination, are effective and useful for LUTS unresponsive to traditional pharmacotherapy. Transurethral resection of the prostate (TURP) can eliminate symptoms of BPH but is associated with relatively more complications than other available surgical and minimally invasive procedures.

M3 muscarinic receptor-like immunoreactivity in sham operated and obstructed guinea pig bladders

PURPOSE

Type 3 muscarinic receptors, which are present in the bladder wall, are important for bladder function. However, their role in the context of the urothelium is not well defined. Understanding the role of type 3 muscarinic receptors has been limited by the lack of specific type 3 muscarinic receptor antibodies. Thus, we identified a specific type 3 muscarinic receptor antibody and investigated the site of type 3 muscarinic receptors in sham operated and obstructed guinea pig bladders.

MATERIALS AND METHODS

The specificity of 4 commercially available type 3 muscarinic receptor antibodies was determined. Immunohistochemistry was then done in bladder tissue from sham operated and obstructed guinea pig bladders.

RESULTS

One of the 4 antibodies examined had the needed specificity in terms of blocking peptide and Western blot characterization. Using this antibody type 3 muscarinic receptor immunoreactivity was associated with muscle cells, nerves and interstitial cells. Four types of interstitial cells were identified, including suburothelial, lamina propria, surface muscle and intramuscular interstitial cells. In the obstructed model the bladder wall was hypertrophied and there was nerve fiber loss. The number of lamina propria, surface muscle and intramuscular interstitial cells was increased but not the number of suburothelial interstitial cells. Also, surface muscle interstitial cells appeared to form clusters or nodes with type 3 muscarinic receptor immunoreactivity.

CONCLUSIONS

Nerve loss and the up-regulation of interstitial cells with type 3 muscarinic receptor immunoreactivity may underlie major functional changes in the pathological bladder. This indicates that type 3 muscarinic receptor specific anticholinergic drugs may affect not only the detrusor muscle, as previously thought, but also interstitial cells and nerve fibers.

Urinary incontinence: pharmacotherapy options

The impact of incontinence is felt by millions of people worldwide, with tremendous decrement in quality of life and enormous cost reaching billions of dollars. Urinary incontinence is defined as 'involuntary leakage of urine' and is categorized into two main types: urgency urinary incontinence (UUI) and stress urinary incontinence (SUI). Behavioral modifications and pharmacologic therapies, primarily antimuscarinic agents, are the mainstay of treatment for UUI. These drugs are moderately efficacious but have troublesome side-effects, the combination resulting in poor compliance and persistence with therapy. There are several agents on the market today, each with some variation in pharmacologic properties. Whether these translate into meaningful differences in clinical efficacy and tolerability remains a matter of debate. Treatment of SUI has seen little success with pharmacologic therapy. In Europe, duloxetine is approved for treatment of SUI with marginal success rates; this drug, although available in the United States for treatment of depression, is not approved for SUI. The search for newer and better pharmacologic options and novel therapies is on-going, fueled primarily by the high prevalence of bothersome incontinence and the tremendous number of health care dollars spent on current therapy. This review addresses pharmacologic options for treatment of urinary incontinence.

Update on the management of overactive bladder: patient considerations and adherence

Overactive bladder (OAB) is a common condition that causes a profound impact on an individual’s overall health and quality of life. Muscarinic receptor antagonists are the mainstay of oral pharmacotherapy for OAB. Although all of the medications in this class are significantly more effective than placebo, they are also associated with more adverse events that may limit their overall use. Although newer preparations of these medications have sought to improve tolerability and efficacy through alternative routes of delivery and once-daily dosing, improved adherence to treatment and treatment persistence continue to be an ongoing challenge. An improved understanding of the factors involved in persistence of medical OAB therapy is imperative in efforts to optimize therapeutic benefits in this chronic and potentially morbid condition.

Antimuscarinics and bladder outlet obstruction: From a contraindication to an indication?

AIM

To review if the existing data support the new concept that antimuscarinic agents can be used for the treatment of bladder outlet obstruction (BOO) with coexisting overactive bladder (OAB).

METHOD

A literature search of Medline publications (up to 2008) on use of antimuscarinic agents for treatment BOO was performed and all data were presented. All relevant data from published studies in congress abstracts were as well included.

RESULTS

The existing data show that this treatment effectively improves patient quality of life. Concerns about the possibility of urinary retention were shown to be unfounded. It seems that antimuscarinic agents do not affect voiding pressures and the use of antimuscarinic agents for BOO seems safe.

CONCLUSIONS

The combination of an alpha-blocker and antimuscarinic agent for the treatment of BOO with concomitant OAB seems promising.

Antimuscarinics and overactive bladder: other mechanism of action

Antimuscarinics are considered first-line treatment for patients with overactive bladder (OAB). However, the mechanism by which antimuscarinics improve the symptoms of OAB remains to be elucidated. Animal studies suggest that antimuscarinics may exert an inhibitory effect on afferent nerves without an effect on detrusor contraction. A release of acetylcholine from the urothelium has been demonstrated in isolated human bladder. In addition, muscarinic receptors (MRs) were found in the urothelium and suburothelial myofibroblasts, suggesting a role for MR mechanisms in urothelial sensory function. Acetylcholine released during the storage phase could be expected to enhance the myogenic contractile activity of the detrusor, which can generate afferent signals. It is suggested that antimuscarinics may decrease bladder afferent activity by blocking MR in the above sites, thereby improving OAB symptoms.

Clinical and experimental aspects of Adreno-muscarinic synergy in the bladder base and prostate

Recent clinical trials have shown that combination therapy using an alpha-receptor antagonist and an antimuscarinic is more effective than either agent alone in improving quality of life and objective urodynamic variables in men with bladder outflow obstruction. There appear to be no negative effects on bladder function. The mode of action of this combination is unknown but presumed to be an antimuscarinic reduction in detrusor overactivity and the alpha-receptor antagonist reduced outflow tract resistance. We have shown with in vitro experiments that in smooth muscles influencing outflow tract resistance (prostate, trigone) there is a profound contractile synergy between adrenergic and muscarinic pathways. We propose the hypothesis that both arms of the combination therapy reduce contractile tone of the outflow tract and that their simultaneous attenuation has a disproportionately large effect on outflow tract resistance. Our data from trigone muscle suggest that adrenergic and muscarinic receptor activation increase the intracellular [Ca(2+)] but the adrenergic pathway also operates through Ca(2+)-sensitisation of the contractile apparatus, primarily through a PKC-dependent pathway.

Oxybutynin chloride topical gel: a new formulation of an established antimuscarinic therapy for overactive bladder

BACKGROUND

Oxybutynin, a cholinergic-muscarinic receptor antagonist, is established as a safe and effective pharmacological treatment for patients with overactive bladder syndrome (OAB). Oxybutynin is available in multiple immediate- and extended-release oral and two transdermal formulations. Oxybutynin chloride topical gel (OTG) (Gelnique), Watson Pharmaceuticals, Corona, CA, USA) was approved in January 2009 by the US FDA. OTG was designed to provide consistent plasma oxybutynin levels with daily application, favorably altering the circulating N-desethyloxybutynin metabolite:oxybutynin ratio, and to utilize a biocompatible delivery system, thus minimizing both the anticholinergic adverse effects of oral formulations and the application-site skin reactions associated with other available forms of transdermal delivery.

OBJECTIVE/METHODS

This review summarizes the pharmacological properties and the clinical efficacy and safety profile of OTG based on the published literature and unpublished data provided by the manufacturer upon request.

RESULTS/CONCLUSION

OTG represents an efficacious, safe, and convenient alternative to other oxybutynin formulations and other oral anticholinergic medications for the treatment of OAB. Future studies and broad clinical experience should confirm the promising early experience observed with this formulation.

The cost-effectiveness of solifenacin vs fesoterodine, oxybutynin immediate-release, propiverine, tolterodine extended-release and tolterodine immediate-release in the treatment of patients with overactive bladder in the UK National Health Service

OBJECTIVE

To assess the cost-effectiveness of solifenacin vs other antimuscarinic strategies commonly used in UK clinical practice, based on the results of a recent published review.

METHODS

Overactive bladder (OAB) syndrome is characterized by symptoms of urgency, frequency, incontinence and nocturia. Pharmacological treatment comprises oral antimuscarinic agents, which are divided into older-generation treatments, including oxybutynin, and new-generation treatments, comprising solifenacin, tolterodine, darifenacin and fesoterodine. The latter have reduced central nervous system penetration and have better selectivity for the M3 subclass of acetylcholine receptors, resulting in improved tolerability. A recent systematic review and meta-analysis of the efficacy and safety of antimuscarinics provided an opportunity for an economic evaluation of these agents using a rigorous assessment of efficacy. A cost-utility analysis was undertaken using a 1-year decision-tree model. Treatment success was defined separately for urgency, frequency and incontinence, with efficacy data taken from the recent review. Treatment persistence rates were taken from the Information Management System database. Utility values for the calculation of quality-adjusted life-years (QALYs) were taken from published sources. The analysis included costs directly associated with treatment for OAB, i.e. antimuscarinic therapy, consultations with general practitioners, and outpatient contacts. Resource use was based on expert opinion. Costs were reported at 2007/2008 prices. Extensive deterministic and probabilistic analyses were conducted to test the robustness of the base-case results.

RESULTS

Solifenacin was associated with the highest QALY gains (per 1000 patients) for all three outcomes of interest, i.e. urgency (712.3), frequency (723.1) and incontinence (695.0). Solifenacin was dominant relative to fesoterodine, tolterodine extended-release (ER) and tolterodine immediate-release (IR), and cost-effective relative to propiverine ER for urgency, frequency and incontinence. Solifenacin was not found to be cost-effective relative to oxybutynin IR for the frequency and incontinence outcomes, with an incremental cost-effectiveness ratio of > pound30,000/QALY threshold.

CONCLUSIONS

Solifenacin provided the greatest clinical benefit and associated QALYs for all three outcomes of interest across all therapies considered, and to be either dominant or cost-effective relative to all other new-generation agents, but not cost-effective relative to oxybutynin for frequency and incontinence.

Relationship between lower urinary tract symptoms and urinary ATP in patients with benign prostatic hyperplasia or overactive bladder

We investigated whether the improvement of lower urinary tract symptoms (LUTS) and urinary adenosine triphosphate (ATP) level were related. Fifty-seven patients and 13 normal controls were enrolled in this study. All of the male patients had benign prostatic hyperplasia (BPH), and all of the female patients had overactive bladder (OAB). We administered an alpha-1 adrenergic receptor antagonist (tamsulosin hydrochloride) for BPH, while OAB patients received an anti-muscarinic agent (propiverine hydrochloride). Before and after treatment, we examined LUTS and urinary ATP/creatinine ratio. The urinary ATP/creatinine ratio was lower in males than females in both controls and patients. In the BPH patients, administration of the alpha-1 receptor antagonist decreased LUTS and urinary ATP/creatinine ratio, and improvement of LUTS was greater in patients with a high baseline urinary ATP level. In the OAB patients, administration of the anti-muscarinic agent decreased LUTS and urinary ATP/creatinine ratio, and improvement of LUTS was greater in patients with a high baseline urinary ATP level. Improvement of LUTS by treatment with the alpha-1 receptor antagonist or the anti-muscarinic agent was related to the decrease of urinary ATP/creatinine ratio in patients with BPH or OAB. Measurement of urinary ATP can be used as a marker of pathologic bladder function.

Role of fesoterodine in the treatment of overactive bladder

Muscarinic receptors have long been the target receptors for treatment of patients with overactive bladder (OAB). These patients experience symptoms of urgency, urinary frequency and nocturia, with or without urge incontinence (the involuntary leakage of urine associated with urge). Fesoterodine, a pro-drug, structurally and functionally related to tolterodine, is the newest agent developed for the treatment of OAB. Fesoterodine is broken down to the active metabolite, 5-hydroxy-methyl-tolterodine (5-HMT) by non-specific esterases. This metabolism results in the complete breakdown of the parent compound and is responsible for dose related improvements in clinical efficacy and health related quality of life. Like other antimuscarinic agents including tolterodine, fesoterodine is associated with improvements in clinical variables related both to bladder filling (decreasing micturition frequency and increasing mean voided volume) and urgency (urgency and urge incontinence episodes). Improvements in health related quality of life following treatment with fesoterodine is indicated by improvements in 7 of the 9 variables measured by the King’s Health Questionnaire. Also like other antimuscarinic agents, fesoterodine use is associated with adverse events including dry mouth. However the incidence of dry mouth is reduced with fesoterodine, compared to oxybutynin, due to the improved bladder selectivity of 5-HMT.

Urinary urgency - translating the evidence base into daily clinical practice

AIM

To consider the currently available knowledge and understanding of the symptom of urgency.

MATERIALS & METHODS

Each faculty member reviewed the literature base of a different aspect of urgency and along with their personal clinical experience provided a base of evidence for discussion.

RESULTS

This overview summarises relevant published literature and the current clinical experience of the authors.

DISCUSSION

Whilst the mechanisms producing the sensation of urgency are still not fully understood and we are working within a definition that may complicate measurement and treatment, our pressing need is to effectively manage our patients for whom the practical nature of urgency can be all too apparent.

CONCLUSION

Health care professionals have an important role to play today in helping to alleviate the widespread problem of urgency and its consequences.

Fesoterodine for the treatment of urinary incontinence and overactive bladder

Overactive bladder (OAB) is a highly prevalent condition, affecting males and females. The prevalence increases with age. Behavioral therapy and antimuscarinic therapy remain the first-line therapies for management of OAB. Despite improvements in symptoms, persistence with antimuscarinic therapy has remained low. Multiple factors including patient expectations, adverse effects and cost may affect persistence. Fesoterodine is one of the newest antimuscarinic agent approved for the management of OAB. It is unique in that it shares the same active metabolite as tolterodine, 5-hydoxymethyltolterodine (5-HMT); however, this conversion is established via ubiquitous esterases and not via the cytochrome P450 system, thus providing a faster and more efficient conversion to 5-HMT. Fesoterodine is available in 2 doses, 4 mg and 8 mg. Clinical trials have established a dose response relationship in efficacy parameters as well as improvements in quality of life. As with all antimuscarinics, dry mouth and constipation are the more common side effects. A combination of medical therapy and behavioral therapy improves the overall outcome in management of OAB. Dose flexibility may help improve efficacy outcomes and patient education on the management of common adverse effects may improve tolerability with these agents.

Fesoterodine for the treatment of overactive bladder

OBJECTIVE

To review pharmacologic, pharmacokinetic, efficacy, and safety data for fesoterodine and determine its role in the treatment of overactive bladder.

DATA SOURCES

A MEDLINE search (1966-July 2009) was conducted using the key words fesoterodine, tolterodine, muscarinic receptor antagonist, anticholinergic, overactive bladder, urge incontinence, efficacy, safety, adverse effect, pharmacology, pharmacokinetic, and receptor binding.

STUDY SELECTION AND DATA EXTRACTION

All articles written in English that were identified from the data sources were evaluated, prioritizing randomized, controlled trials with human data. The references of published articles that we identified were examined for any additional studies appropriate for the review.

DATA SYNTHESIS

Fesoterodine, a competitive muscarinic receptor antagonist, is converted to its active metabolite, 5-hydroxymethyltolterodine, by nonspecific esterases, bypassing the cytochrome P450 system. Two randomized controlled Phase 3 trials examined the safety and efficacy of fesoterodine in the treatment of overactive bladder. Fesoterodine was found to produce significant improvements in the treatment of overactive bladder symptoms compared with placebo. Post hoc analysis of these trials demonstrated significant improvements in health-related quality of life in patients with overactive bladder. Only one study included tolterodine, and direct comparisons between fesoterodine and tolterodine were not conducted. The most common treatment-emergent adverse effects associated with fesoterodine included dry mouth, constipation, urinary tract infection, and headache.

CONCLUSIONS

Fesoterodine appears to be effective and generally safe for the treatment of overactive bladder. The efficacy and safety of fesoterodine in overactive bladder treatment seem to be at least similar to that of tolterodine. Although additional comparative trials are needed, based on available data, it does not appear that fesoterodine provides a substantial advantage over extended-release tolterodine in either efficacy or safety.

A refocus on the bladder as the originator of storage lower urinary tract symptoms: a systematic review of the latest literature

CONTEXT

The focus of clinical understanding and management of male storage lower urinary tract symptoms (LUTS) has shifted from the prostate to the bladder. This is mirrored by an increasing body of experimental evidence suggesting that the bladder is the central organ in the pathogenesis of LUTS.

OBJECTIVE

A systematic review of the literature available on pathophysiologic aspects of storage LUTS.

EVIDENCE ACQUISITION

Medline was searched for the period ending December 2008 for studies on human and animal tissue exploring possible functional and structural alterations underlying bladder dysfunction. Further studies were chosen on the basis of manual searches of reference lists and review papers.

EVIDENCE SYNTHESIS

Numerous recent publications on LUTS pathophysiology were identified. They were grouped into studies exploring abnormalities on urothelial/suburothelial, muscular, or central levels.

CONCLUSIONS

Studies revealed both structural and functional alterations in bladders from patients with LUTS symptoms or animals with experimentally induced bladder dysfunction. In particular, the urothelium and the suburothelial space, containing afferent nerve fibres and interstitial cells, have been found to form a functional unit that is essential in the process of bladder function. Various imbalances within this suburothelial complex have been identified as significant contributors to the generation of storage LUTS, along with potential abnormalities of central function.

Tolterodine extended release is well tolerated in older subjects

OBJECTIVES

To investigate the tolerability of tolterodine extended release (ER) in older subjects with overactive bladder (OAB).

METHODS

This was a retrospective analysis of pooled data from five large, randomised, double-blind, placebo-controlled trials. Subjects with OAB symptoms, including urinary frequency and urgency (and nocturia in two studies) with or without urgency urinary incontinence, received qd treatment with tolterodine ER (4 mg) or placebo for 8-12 weeks. Data were stratified post hoc by age group: < 65 (n = 2531), 65-74 (n = 1059) and > or = 75 years (n = 573). Tolerability was assessed by evaluating the occurrence of adverse events (AEs). AE occurrences from each study were mapped to the MedDRA coding dictionary of preferred terms.

RESULTS

Discontinuation rates were slightly higher among subjects > or = 75 years of age vs. those < 65 years of age; however, this was observed in subjects treated with placebo as well as tolterodine ER. Overall, there were no significant differences in the occurrence of dry mouth, headache, constipation, nausea, urinary tract infection, blurred vision, dry eye, dizziness and micturition disorder in older (65-74 or > or = 75 years) vs. younger (< 65 years) subjects treated with tolterodine ER relative to placebo (treatment x age; all p > 0.1). Dry mouth was the only AE consistently associated with tolterodine ER treatment (< 65 years, 17%; 65-74 years, 16%; > or = 75 years, 15%). The occurrence of all other AEs was < or = 5% in most age and treatment cohorts. Most AEs were mild or moderate in all age and treatment cohorts.

CONCLUSION

The nature and frequency of AEs associated with tolterodine ER treatment were similar across age groups in subjects with OAB, suggesting that tolterodine ER was not associated with an increased risk of AEs in older vs. younger subjects and, thus, is a suitable first-line pharmacotherapy treatment for OAB in this population.

Comparison of the effect of anti-muscarinic agents on bladder activity, urinary ATP level, and autonomic nervous system in rats

We compared the effect of 4 anti-muscarinic agents on bladder activity, urinary ATP levels, and autonomic nervous system in rats. Rats were divided into the following 5 groups (control group, oxybutynin group, propiverine group, tolterodine group, imidafenacin group), and were administered daily the designated anti-muscarinic agent or distilled water into the stomach. After 2 weeks, we performed 1) continuous cystometry with physiological saline and 0.1% acetic acid solution, 2) measurement of urinary ATP level before and after bladder stimulation, and 3) measurement of the heart rate, blood pressure and plasma catecholamines. The maximum bladder contraction pressure increased and the interval between contractions became shorter during cystometry with acetic acid solution in the control group, but not in the 4 anti-muscarinic agent groups. The urinary ATP level increased after bladder stimulation in all groups, but the increase was smaller in the propiverine and imidafenacin groups. The plasma noradrenaline and dopamine levels of the propiverine group were higher. Taken together, all anti-muscarinic agents inhibited the bladder activity without changing the heart rate and blood pressure. Especially, the inhibitory effect of propiverine and imidafenacin on bladder activity may be partly due to blocking an increase of ATP release from the bladder urothelium.