Intravesical oxybutynin: a local anesthetic effect on bladder C afferents

[Short version of the S2k guideline on drug therapy of neurogenic lower urinary tract dysfunction (NLUTD)]

BACKGROUND

In Germany about one million patients suffer from neurogenic lower urinary tract dysfunction (NLUTD). If left untreated, various forms of NLUTD can lead to secondary damage of the lower and upper urinary tract. Thus, the guideline was developed for the drug therapy of patients with NLUTD, who frequently require lifelong care and aftercare.

METHODS

The guideline was developed in a consensus process with several meetings and online reviews, and final recommendations were decided on in online consensus meetings. Ballots were sent to elected officials of the contributing professional societies. Level of consensus was given for each coordinated recommendation ( https://www.awmf.org/leitlinien/detail/ll/043-053.html ). RESULTS/MOST IMPORTANT RECOMMENDATIONS: (Video)urodynamic classification of the NLUTD should be conducted before the use of antimuscarinic drugs (84.2%). Approved oral antimuscarinics should be used as first choice. Contraindications must be respected (100%). If oral treatment is ineffective or in the case of adverse drug reaction (ADRs) alternatively instillation of oxybutynin solution intravesically (83%) or onabotulinumneurotoxine (OBoNT) injection should be offered (89.5%). In case of failure or ADRs of antimuscarinics, β3 sympathomimetic mirabegron can be used to treat neurogenic detrusor overactivity (NDO) (off-label use) (100%). In case of paraplegia below C8 or multiple sclerosis with an expanded disability status scale (EDSS) of ≤ 6.5, OBoNT injection can be offered as an alternative (89.5%). Drug therapy for NDO should be started early in newborns/young children (84.2%). Conservative, nondrug therapy should be considered in frail elderly (94.7%). No parasympathomimetic therapy should be used to treat neurogenic detrusor underactivity (94.7%).

CONCLUSION

Precise knowledge of the neurological underlying disease/sequence of trauma and the exact classification of the NLUTD are required for development of individualized therapy.

Partial recovery of voiding function in female mice following repeated psychological stress exposure

Psychological stress causes bladder dysfunction in humans and in rodent models, with increased urinary frequency and altered contractile responses evident following repeated environmental stress exposure. However, whether these changes persist after removal of the stressor is unknown, and the aim of this study was to determine if stress-induced changes in voiding behaviour and bladder function recover following removal of the stressor. Adult female mice were allocated to three groups: Unstressed, Stressed or Stressed + Recovery. Animals in the stressed groups were exposed to water avoidance stress for 1h/day for 10-days, with unstressed animals age-matched and housed under normal conditions. For recovery studies, animals were housed without stress exposure for an additional 10-days. Voiding behaviour was assessed periodically and animals sacrificed on day 10 (Unstressed and Stressed) or day 20 (Unstressed and Stressed + Recovery). Isolated whole bladder studies were used to assess compliance, urothelial mediator release and contractile responses. Exposure to stress increased plasma corticosterone levels almost three-fold (P<0.05) but this returned to baseline during the recovery period. Contractile responses of the bladder to carbachol and KCl were also increased following stress, and again fully recovered after a 10-day stress-free period. In contrast, stress increased urinary frequency four-fold (P<0.001), but this did not return fully to baseline during the recovery period. Bladder compliance was unchanged by stress; however, it was increased in the stressed + recovery group (P<0.05). Thus, following a stress-free period there is partial recovery of voiding behaviour, with an increase in bladder compliance possibly contributing to the compensatory mechanisms.

Evaluation of Choline and Acetylcholine Levels in Responders and Nonresponders to Anticholinergic Therapy for Overactive Bladder Syndrome

OBJECTIVE

This study aimed to determine whether levels of choline (Ch) and acetylcholine (Ach) differ between responders and nonresponders to anticholinergic therapy.

METHODS

Patients prescribed an anticholinergic were evaluated using the Overactive Bladder Symptom Score; Medical, Epidemiologic and Social Aspects of Aging and Incontinence Questionnaire; and Incontinence Impact Questionnaire-7. A 1-day voiding diary and a urine sample were collected. After treatment for 12 weeks, the questionnaires were administered and 1-day voiding diary was completed. Levels of Ach and Ch were measured by liquid chromatography with tandem mass spectrometry. Subjects were divided into responders and nonresponders. Wilcoxon rank sum test and Fisher exact test were used to express differences between groups. Spearman ρ correlation coefficient was used to determine the relationship between Ach and Ch and symptom severity, patient demographics, and questionnaire scores.

RESULTS

Thirty-one women were included in the analysis. The treatment response rate was 48.8%. The median age was 67 years (interquartile range, 50-76 years), and median body mass index was 32.3 kg/m2 (27.5-40.6 kg/m2), with 41.2% having an additional complaint of stress incontinence. There were no significant differences in symptom severity or questionnaire scores between groups.The median Ch and Ach levels were higher in responders (28.6 vs 9.2 μL, P = 0.04) and (83.1 vs 18.7 nL, P = 0.02), respectively. Levels of both Ch and Ach had moderate positive correlations with the Medical, Epidemiologic and Social Aspects of Aging and Incontinence Questionnaire urgency urinary incontinence score (ρ = 0.533 [P = 0.002] and ρ = 0.453 [P = 0.01], respectively).

CONCLUSION

In women with overactive bladder, urinary Ach and Ch levels are higher in responders to anticholinergic therapy compared with nonresponders.

Combinational effects of muscarinic receptor inhibition and β3-adrenoceptor stimulation on neurogenic bladder dysfunction in rats with spinal cord injury

AIMS

To investigate the effects of combined therapy with an anticholinergic agent and a β3-adrenoceptor agonist on bladder dysfunction and proliferation-related molecule expression in rats with spinal cord injury (SCI).

METHODS

The spinal cord was transected at the level of T8-9 in female Sprague-Dawley rats, which were divided into four groups; A: Vehicle, B: 10 mg/kg/day of oxybutynin, C: 10 mg/kg/day of mirabegron, and D: combined administration of oxybutynin and mirabegron. Drugs were administered by oral gavage from 2 to 4 weeks after spinal cord transection. We evaluated urodynamic parameters and bladder tissue remodeling factors.

RESULTS

Non-voiding contractions (NVCs) during the storage phase of cystometrograms tended to be decreased in all three treated groups with a significant reduction in group D versus A. Bladder compliance was improved, and intercontraction intervals, voided volume and bladder capacity were increased in group D. In all three treated groups (B-D), the expression of HIF1-α and TGF-β1 was decreased compared to group A. The expression of collagen-III and bFGF was decreased in groups B and D. The total bladder elastin level was increased in group D.

CONCLUSIONS

The combination therapy of an anticholinergic agent and a β3-adrenoceptor agonist elevated the bladder elastin level, reduced NVCs, and increased bladder compliance more effectively than the monotherapy in SCI rats. Thus, the combination therapy could be effective for the treatment of neurogenic bladder dysfunction including bladder remodeling. Neurourol. Urodynam. 36:1039-1045, 2017. © 2016 Wiley Periodicals, Inc.

Modulation of afferent nerve activity by prostaglandin E2 upon urinary bladder distension in rats

NEW FINDINGS

What is the central question of this study? It has been widely assumed that C fibres innervating the bladder are mainly excited in overactive bladder syndrome. However, it remains unclear whether Aδ fibres are also activated in pathological conditions. What is the main finding and its importance? We found that a certain population of Aδ fibres, which become active specifically at a bladder pressure of more than 15 cmH2 O in normal conditions, showed increased excitability in conditions of prostaglandin E2 -induced overactive bladder. This result suggests that a certain population of Aδ fibres, together with C fibres, triggers pathophysiological activity. In overactive bladder syndrome, afferent C fibres innervating the bladder show an increased activity level. However, it remains unclear whether all C fibres are highly activated and whether Aδ fibres, the other type of bladder afferent fibre, are also involved in pathological conditions. To address these questions, we analysed the relationship between bladder pressure and single-unit firing patterns of afferent nerves in the left L6 dorsal roots in living rats. The recorded fibres were classified as Aδ fibres or C fibres based on the response to 0.3 μm tetrodotoxin. Certain populations of both Aδ fibres and C fibres were activated at bladder pressures below 15 cmH2 O (classified as low-threshold fibres), indicating their potential contribution to detection of normal bladder filling. Intravesical administration of prostaglandin E2 (PGE2 ) induced hyperexcitation in approximately half of such C fibres, whereas the activity patterns of low-threshold Aδ fibres were unchanged. All fibres, regardless of type, which were almost silent in control conditions (classified as high-threshold fibres), were activated by application of PGE2 . Notably, the firing patterns of Aδ fibres, rather than C fibres, were highly time locked to PGE2 -induced micro-oscillation of bladder pressure. These modulatory effects of PGE2 on Aδ fibres and C fibres might trigger pathophysiological activity together in overactive bladder syndrome.

Delivery methods for drugs used in the treatment of overactive bladder

INTRODUCTION

Overactive bladder affects a significant portion of the population and results in prescribing of numerous medications for its treatment. Traditional drug delivery systems used in therapy are associated with multiple commonly reported side effects. Adherence rates with use of these medications are low. It is likely that low adherence rates with the use of these drugs are due in some part to drug side effects. It is therefore important that alternate methods for drug delivery be explored to reduce side effect profiles and improve patient compliance.

AREAS COVERED

This article addresses the various forms of drug delivery for overactive bladder medications, focusing on those currently in use. Newer systems of drug delivery are also discussed. Through thorough review of research data, randomized trials and meta analyses, drug delivery systems were evaluated.

EXPERT OPINION

EXPERT OPINION favors the use of the transdermal patch and recognizes the necessity for further research and development of other delivery methods. The patch delivery method offers the most effective means of treating symptoms and minimizing drug related adverse side effects leading to treatment discontinuation. Development of OAB medications aimed at alternate receptor targets has the potential to facilitate the creation of new treatment methods to compete with the current standard of care used in OAB treatment.

Chronic administration of anticholinergics in rats induces a shift from muscarinic to purinergic transmission in the bladder wall

BACKGROUND

First-line pharmacotherapy for overactive bladder consists of anticholinergics. However, patient compliance is exceptionally low, which may be due to progressive loss of effectiveness.

OBJECTIVE

To decipher the involved molecular mechanisms and to evaluate the effects of chronic systemic administration of anticholinergics on bladder function and on muscarinic and purinergic receptors expression in rats.

DESIGN, SETTING, AND PARTICIPANTS

Female Wistar rats were implanted with an osmotic pump that chronically administered vehicle (Vehc), 0.36 mg/kg per day oxybutynin (Oxyc), or 0.19 mg/kg per day fesoterodine (Fesoc) for 28 d.

INTERVENTIONS

For cystometry experiments, a small catheter was implanted in the bladder.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

Urologic phenotype was evaluated by the analysis of the micturition pattern and urodynamics. Expression of muscarinic and purinergic receptors was assessed by Western blot analysis of detrusor membrane protein. Functional responses to carbachol and adenosine triphosphate (ATP) were evaluated using muscle-strip contractility experiments.

RESULTS AND LIMITATIONS

The number of voided spots was transiently decreased in Oxyc rats. In Oxyc rats, the effect of an acute high dose of oxybutynin (1mg/kg intraperitoneally [IP]) on the intermicturition interval was abolished. Expression experiments revealed a decrease of muscarinic acetylcholine receptors M2 (mAChR2) and M3 (mAChR3), whereas the purinergic receptor P2X, ligand-gated ion channel, 1 (P2X1) was enhanced in Oxyc and Fesoc rats compared to Vehc rats. In concordance with the modification of the expression pattern in Oxyc rats, the force generated by carbachol and ATP in muscle-strip contractility experiments was, respectively, lower and higher. Urodynamics revealed that the effects of systemic administration of the purinergic blocker pyridoxalphosphate-6-azophenyl-2',4'-disulphonic acid (50mg/kg IP) were enhanced in Oxyc rats. As rat bladder physiology is different from that of humans, it is difficult to directly extrapolate our findings to human patients.

CONCLUSIONS

Chronic administration of anticholinergics in rats induces receptor loss of efficiency and a shift from muscarinic to purinergic transmission.

Urothelial signaling

The urothelium, which lines the inner surface of the renal pelvis, the ureters, and the urinary bladder, not only forms a high-resistance barrier to ion, solute and water flux, and pathogens, but also functions as an integral part of a sensory web which receives, amplifies, and transmits information about its external milieu. Urothelial cells have the ability to sense changes in their extracellular environment, and respond to chemical, mechanical and thermal stimuli by releasing various factors such as ATP, nitric oxide, and acetylcholine. They express a variety of receptors and ion channels, including P2X3 purinergic receptors, nicotinic and muscarinic receptors, and TRP channels, which all have been implicated in urothelial-neuronal interactions, and involved in signals that via components in the underlying lamina propria, such as interstitial cells, can be amplified and conveyed to nerves, detrusor muscle cells, and ultimately the central nervous system. The specialized anatomy of the urothelium and underlying structures, and the possible communication mechanisms from urothelial cells to various cell types within the bladder wall are described. Changes in the urothelium/lamina propria ("mucosa") produced by different bladder disorders are discussed, as well as the mucosa as a target for therapeutic interventions.

Autonomic nervous control of the urinary bladder

The autonomic nervous system plays an important role in the regulation of the urinary bladder function. Under physiological circumstances, noradrenaline, acting mainly on β(3) -adrenoceptors in the detrusor and on α(1) (A) -adrenoceptors in the bladder outflow tract, promotes urine storage, whereas neuronally released acetylcholine acting mainly on M(3) receptors promotes bladder emptying. Under pathophysiological conditions, however, this system may change in several ways. Firstly, there may be plasticity at the levels of innervation and receptor expression and function. Secondly, non-neuronal acetylcholine synthesis and release from the urothelium may occur during the storage phase, leading to a concomitant exposure of detrusor smooth muscle, urothelium and afferent nerves to acetylcholine and noradrenaline. This can cause interactions between the adrenergic and cholinergic system, which have been studied mostly at the post-junctional smooth muscle level until now. The implications of such plasticity are being discussed.

From urothelial signalling to experiencing a sensation related to the urinary bladder

The mechanisms underlying bladder sensation and the way we experience sensations during normal voiding and in pathology is complex and not well understood. During storage and emptying, mechanical changes occurring in number of cell types within the bladder wall (i.e. the uroepithelium and bladder afferents) can have a major influence on our sensory systems. In this review, we discuss bladder sensation with a focus on coding events in the periphery.

Overactive bladder, differential diagnosis, and clinical utility of fesoterodine

Overactive bladder is a symptom syndrome with urgency, frequency and, in many cases, nocturia. Urge incontinence is not present in all. There is no direct correlation with detrusor overactivity, an objective finding during urodynamic testing where involuntary contractions can be noticed. In the pathophysiology, much more attention has been given to the afferent/sensory arm of the micturition reflex in the last decade. Anatomical and infectious causes have to be diagnosed or ruled out. Diagnosis of overactive bladder is made mostly by history-taking, but other tests can be necessary in specific patients. Treatment consists of behavioral measures, a good explanation of the condition, training, and pelvic floor physiotherapy. Drugs are often used. Until recently, antimuscarinic drugs have been the mainstay of pharmacological therapy. Fesoterodine is a newer antimuscarinic agent which is more pharmacodynamically stable then tolterodine. Fesoterodine has been extensively researched using different dosages and compared with placebo and tolterodine, in different age groups, and under different conditions. Fesoterodine is superior to placebo and to tolterodine in the short term and long term. Its safety is very acceptable.

Effects of mirabegron, a novel β3-adrenoceptor agonist, on primary bladder afferent activity and bladder microcontractions in rats compared with the effects of oxybutynin

BACKGROUND

Mirabegron is the first β3-adrenoceptor agonist that is clinically effective for overactive bladder.

OBJECTIVE

The effects of mirabegron on primary bladder mechanosensitive single-unit afferent activities (SAAs) and bladder microcontractions were evaluated and compared with the effects of oxybutynin.

DESIGN, SETTING, AND PARTICIPANTS

Female Sprague-Dawley rats were anesthetized. The SAAs generated from left L6 dorsal roots were identified by electrical stimulation of the left pelvic nerve and bladder distension. Nerves with conduction velocities (CVs) >2.5 m/s were designated as Aδ-fibers, and nerves with CVs<2.5 m/s were designated as C-fibers.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

Two measurements were performed in separate animals. First, after measuring the baselines of SAA during constant filling cystometry, the procedure was repeated with each intravenous administration of mirabegron at three doses-0.1, 0.3, and 1.0mg/kg-cumulatively. Second, the bladder was filled with saline until the intravesical pressure reached 30 cm H(2)O and was kept under an isovolumetric condition; then the recording was performed for 5 min with vehicle and mirabegron or oxybutynin administrated intravenously.

RESULTS AND LIMITATIONS

A total of 74 single-unit afferent fibers were isolated from 55 rats (Aδ-fibers: n=34; C-fibers: n=40). SAAs of both Aδ-fibers and C-fibers in response to bladder filling significantly decreased after mirabegron administration in a dose-dependent manner, which was more remarkable for Aδ-fibers. During an isovolumetric condition of the bladder, the mean bladder pressure and the number of microcontractions decreased after mirabegron administration, whereas these parameters did not change with oxybutynin administration. SAAs of Aδ-fibers were significantly decreased by mirabegron administration at both 0.3 and 1mg/kg, whereas SAAs of C-fibers decreased only at 1mg/kg. In contrast, oxybutynin (1mg/kg) did not alter either type of SAA.

CONCLUSIONS

The present study demonstrates that mirabegron can inhibit mechanosensitive bladder afferent activity, especially of Aδ-fibers, which may be related to suppression of bladder microcontractions.

Inhibitory effects of phosphodiesterase 5 inhibitor, tadalafil, on mechanosensitive bladder afferent nerve activities of the rat, and on acrolein-induced hyperactivity of these nerves

What's known on the subject? and What does the study add? Tadalafil, a phosphodiesterase type 5 inhibitor, might be effective for not only erectile dysfunction but also lower urinary tract symptoms (LUTS). One of the mechanisms of tadalafil on LUTS is added in the study.

OBJECTIVE

To determine if tadalafil, a phosphodiesterase type 5 inhibitor, decreases afferent nerve activity from the bladder with and without chemical stimulation by intravesical acrolein instillation.

MATERIALS AND METHODS

Female Sprague-Dawley rats were used. Under urethane anaesthesia, single afferent fibres of the nerve primarily originating from the bladder were identified by electrical stimulation of the pelvic nerve and by bladder distension, and classified by conduction velocity as Aδ- or C-fibres. After measuring the baseline single afferent activities (SAA) during constant filling, two experiments were performed. First, tadalafil was administrated intravenously (i.v.) at three doses, 0.01, 0.03 and 0.1 mg/kg cumulatively and SAA were repeatedly studied after each administration. Second, in the presence of vehicle or tadalafil (0.1 mg/kg) i.v., the effect of intravesical instillation of acrolein (0.003%) was studied.

RESULTS

In all, 39 single units were isolated (Aδ-fibres 21; C-fibres, 18) in 25 rats. Tadalafil dose-dependently decreased SAA of both Aδ- and C-fibres during saline instillation. Intravesical acrolein facilitated SAA of both fibres after vehicle administration. Pretreatment with tadalafil significantly inhibited the acrolein-induced hyperactivity of both fibres.

CONCLUSION

Our study shows, using selective unifibre potential measurement, that systemic administration of tadalafil reduces mechanosensitive afferent activities of both Aδ- and C-fibres elicited by bladder distension in the rat, and also that tadalafil has an inhibitory effect on the increased activities of both fibres induced by intravesical acrolein instillation.

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.

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.

An overview of the clinical use of antimuscarinics in the treatment of overactive bladder

Overactive bladder is a common and bothersome condition. Antimuscarinic agents, as a class, are the cornerstone of medical treatment of overactive bladder. They offer significant improvements in symptoms and patients' quality of life. Antimuscarinics are generally well tolerated with mild and predictable side effects. Available antimuscarinics have small, yet statistically significant, differences in their efficacy and tolerability profiles. In clinical practice, finding the agent that offers the optimum balance of efficacy and side effects for an individual patient remains the major challenge.

Specific pharmacokinetic aspects of the urinary tract

This chapter reviews the evidence for "specific" pharmacokinetics playing a role in currently marketed drugs intended to treat lower urinary tract (LUT) symptoms. Principles of drug targeting include intrinsic properties of drugs or organs as well as drug formulations to modify drug release or to create confinement of drug presence. Prodrugs and specific formulations to deliver high drug concentrations at the site(s) of action as well as other ways to manipulate drug distribution to achieve enrichment in target tissues are considered. In overactive bladder (OAB), specific formulations for oxybutynin have been introduced to reduce the level of side effects of the active drug. Extended release tablet formulations and a topical gel formulation have been introduced, with efficacy similar to immediate release (IR) tablets, but with a reduction in anticholinergic adverse effects. However, these modifications have not led to outstanding performance parameters compared to other anticholinergic drugs marketed as IR formulations. Urinary excretion is discussed as potential mechanism for targeting LUT symptoms, but no strong indications appear to exist that this mechanism would contribute for currently available drugs. Intravesical administration of drugs is not a preferred option and only considered for drugs like botulinum toxin, where the inconvenient application compensates for a reasonable degree of long-term efficacy in severe refractory OAB. Alpha acid glycoprotein binding is discussed as a potential factor to influence drug tissue distribution, and it is concluded that there is reasonable evidence that for tamsulosin this mechanism is responsible for the difference in free fraction of the drug observed in plasma and prostate, which could contribute to its relative absence of blood pressure effects in patients with LUT symptoms related to benign prostate hyperplasia (LUTS-BPH). The principle of irreversible inhibition of type II 5α-reductase as a tool to develop drugs to reduce prostatic levels of dihydrotestosterone is employed by both dutasteride and finasteride for treatment of LUTS-BPH. Of the mechanisms discussed, the principles employed for the 5α-reductase blockers and tamsulosin in this respect can be considered relatively specific for its urological indication.

Afferent mechanism in the urinary tract

Much of the current research on lower urinary tract dysfunction is focused on afferent mechanisms. The main goals are to define and modulate the signaling pathways by which afferent information is generated and conveyed to the central nervous system. Alterations in bladder afferent mechanisms are a potential source of voiding dysfunction and an emerging source of drug targets. Even some established drug therapies such as muscarinic receptor antagonists, as well as emerging therapies such as botulinum toxin type-A, may act partly through afferent mechanisms. This review presents up-to-date findings on the localization of afferent fiber types within the bladder wall, afferent receptors and transmitters, and how these may communicate with the urothelium, interstitial cells, and detrusor smooth muscle to regulate micturition in normal and pathological bladders. Peripheral and central mechanisms of afferent sensitization and myogenic mechanisms that lead to detrusor overactivity, overactive bladder symptoms, and urgency sensations are also covered as well as new therapeutic approaches and new and established methods of measuring afferent activity.

Effects of CL316,243, a beta 3-adrenoceptor agonist, and intravesical prostaglandin E2 on the primary bladder afferent activity of the rat

AIMS

It has been suggested that beta(3)-adrenoceptor (beta(3)-AR) agonists affect not only the efferent but also the afferent pathways innervating the bladder. In addition, prostaglandin E(2) (PGE(2)) causes bladder hyperactivity in conscious rats. We investigated the direct effects of a beta(3)-AR agonist (CL316,243; CL) and PGE(2) on single fiber activities of the primary bladder afferent nerves.

METHODS

Female Sprague-Dawley rats were used. Under urethane anesthesia, a single nerve fiber primarily originating from the bladder was identified by electrical stimulation of the left pelvic nerve and by bladder distention, and was divided by conduction velocity (2.5 m/sec) as A delta-fiber or C-fiber. The afferent activity measurements with constant bladder filling were repeated three times and the third measurement served as the base-line observation. Then, CL (10 microg/kg) or its vehicle was administrated intravenously. Thereafter, 10(-4) M of PGE(2) or saline was instilled intravesically and another three cycles recorded.

RESULTS

Forty-three single afferent fibers (A delta-fibers: n = 20, C-fibers: n = 23) were isolated from 34 rats. Intravenous administration of CL, but not vehicle, significantly decreased A delta-fiber, but not C-fiber, activities in response to bladder filling with saline. Intravesical instillation of PGE(2) significantly increased C-fiber activities, but not A delta-fiber activities. The PGE(2)-induced increase in C-fiber activities was inhibited by pretreatment with CL.

CONCLUSIONS

The present results clearly demonstrate that the beta(3)-AR agonist, CL316,243, can inhibit the mechanosensitive A delta-fibers, but not the C-fibers, of the primary bladder afferents of the rat. In addition, the beta(3)-AR agonist can inhibit PGE(2)-induced C-fiber hyperactivity.

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.

Effects of stimulation of muscarinic receptors on bladder afferent nerves in the in vitro bladder-pelvic afferent nerve preparation of the rat

Effects of a muscarinic receptor agonist oxotremorine-M (oxo-M) on bladder afferent nerve (BAN) activity were studied in an in vitro bladder-pelvic nerve preparation. Distension of the bladder induced rhythmic bladder contractions that were accompanied by multiunit afferent firing. Intravesical administration of 25 and 50 μM oxo-M significantly increased afferent firing from 41 ± 2 spikes/s to 51 ± 4 spikes/s and 60.5 ± 5 spikes/s, respectively, but did not change the maximum amplitude of spontaneous bladder contractions. The afferent nerve firing induced by isotonic distension of the bladder (10-40 cmH(2)O) was increased 22-100% by intravesical administration of 50 μM oxo-M. Electrical stimulation on the surface of the bladder elicited action potentials (AP) in BAN. Oxo-M significantly decreased the voltage threshold by 40% (p<0.05) and increased by 157% (p<0.05) the area of the AP evoked at a submaximal stimulus intensity. These effects were blocked by intravesical injection of 5 μM atropine methyl nitrate (AMN). Intravesical administration of 5 μM AMN alone did not alter BAN firing or the amplitude of bladder contractions. The facilitatory effects induced by oxo-M on BAN activity were also suppressed (p<0.05) by intravesical administration of 2',3'-0-trinitrophenyl-ATP (TNP-ATP) (30 μM). In preparations pretreated with capsaicin (125 mg/kg, s.c.) the facilitatory effects of 50 μM oxo-M on BAN activity were absent. These results suggest that activation of muscarinic receptors facilitates mechano-sensitive, capsaicin-sensitive BAN activity in part by mechanisms involving purinergic receptors located near the luminal surface of the bladder and ATP release which presumably occurs in the urothelium.

Effects of intravesical instillation of ATP on rat bladder primary afferent activity and its relationship with capsaicin-sensitivity

AIMS

Previous studies have suggested that ATP has a role in mechano-afferent transduction, at least partly mediated by nerves other than capsaicin (Cap)-sensitive nerves. We investigated the direct effect of ATP on single fiber activity (SFA) of the primary bladder afferent nerves and its relationship with Cap-sensitivity.

METHODS

Female Sprague-Dawley rats were used. On the basis of conduction velocities, SFA was grouped as Aδ- or C-fibers. First, SFA and intravesical pressure were measured during filling as the baseline. Then, Cap (10(-5) M) was instilled intravesically and the SFA response was monitored. To desensitize Cap-sensitive nerves, resiniferatoxin (RTX) (10(-6) M) was administered intravesically, and then Cap was again administered to confirm the desensitization effect. Thereafter, ATP (10(-3) M) or its vehicle was instilled intravesically and another filling cycles recorded.

RESULTS

Thirty-two single afferent fibers were discriminated. Aδ-fibers did not respond to intravesical instillation of Cap, RTX or ATP. Based on Cap-sensitivity, C-fibers could be divided into two subtypes: Cap-sensitive (n=8) and Cap-insensitive (n=16). In the Cap-sensitive C-fibers, the response to bladder filling mostly disappeared after RTX desensitization, no matter if the bladder was filled with vehicle or ATP. On the other hand, in the Cap-insensitive C-fibers, even after RTX-treatment, the response was preserved and more enhanced when the bladder was filled with ATP compared to vehicle.

CONCLUSIONS

Mechanosensitive bladder afferents can be classified as (1) Aδ-fibers, (2) Cap-insensitive, and (3) Cap-sensitive C-fibers. The activation of the bladder afferents induced by intravesical application of ATP is mediated mainly through Cap-insensitive C-fibers.

Rehabilitation in Practice: Neurogenic lower urinary tract dysfunction and its management

This series of articles for rehabilitation in practice aims to cover a knowledge element of the rehabilitation medicine curriculum. Nevertheless they are intended to be of interest to a multidisciplinary audience. The competency addressed in this article is ‘the trainee consistent demonstrates a knowledge of the pathophysiology of various specific impairments including bladder dysfunction’ and ‘management approaches for specific impairments including bladder dysfunction’. The lower urinary tract (bladder and urethra) has two roles: storage of urine and emptying at appropriate times. The optimal and coordinated activity of the lower urinary tract is subject to a complex neural control which involves all levels of the nervous system, from cortex to peripheral innervation. The complexity of the neural control of lower urinary tract explains the high prevalence of urinary disturbances in neurologic disease. Information obtained from history taking and supplemented by use of a bladder diary forms the cornerstone of evaluation. Ultrasonography is used to assess the degree of incomplete bladder emptying, and for assessing the upper tracts. Urodynamic tests, with or without simultaneous fluoroscopic monitoring, assess detrusor and bladder outlet function and give fundamental information about detrusor pressure and thus the risk factor for upper tract damage. Impaired emptying is most often managed by clean intermittent self-catheterization and this should be initiated if the post-void residual urine is greater than 100 mL or exceeds one third of bladder capacity, or rarely if spontaneous voiding is dangerous due to high detrusor pressure. Storage symptoms are most often managed using antimuscarinic medications. Other options include desmopressin to reduce urine output or intradetrusor injection of botulinum toxin type A to reduce detrusor overactivity. Understanding of the underlying mechanism of lower urinary tract dysfunction is crucial for effective management.

Oxybutynin and propiverine suppress adenosine triphosphate-induced bladder overactivity other than through antimuscarinic mechanisms

OBJECTIVES

Adenosine triphosphate (ATP) is released from bladder urothelium in response to stretch and may act as a sensory neurotransmitter. ATP release from the bladder urothelium is augmented in many pathophysiologic conditions, resulting in bladder overactivity. Patients who have bladder overactivity are treated with antimuscarinics with symptom improvement. We investigated the effects of oxybutynin and propiverine on bladder overactivity induced by intravesical instillation of ATP.

MATERIAL AND METHODS

Under urethane anesthesia, cystometry was performed in female Sprague-Dawley rats. After a 2-hour baseline period, protamine sulfate (10 mg/mL) was instilled for 1 hour, and then ATP (60 mM, pH 6.0) was instilled intravesically. Oxybutynin, propiverine, pyridoxal-(5) phosphate-6-azophenyl-2',4'-disulfonic acid (PPADS), atropine, 4-diphenylacetoxy-N-methylpiperidine methobromide (4-DAMP), and methoctramine were given intravenously when ATP-induced bladder overactivity was stable.

RESULTS

When protamine sulfate was infused intravesically, the intercontraction interval (ICI) did not decrease significantly, but intravesical instillation of ATP after protamine sulfate treatment decreased the ICI compared with baseline. Oxybutynin, propiverine, and PPADS given intravenously reversed the ATP-induced ICI reduction in a dose-dependent manner. In contrast, ATP-induced ICI reduction was not reversed by intravenous atropine, 4-DAMP, or methoctramine. Maximum voiding pressure did not change with ATP but decreased with antimuscarinics. Pressure threshold (PT) decreased with ATP and stayed reduced after dose of oxybutynin or propiverine.

CONCLUSIONS

Bladder overactivity induced by intravesical instillation of ATP with protamine pretreatment was suppressed by oxybutynin, propiverine, and PPADS, and not by atropine, 4-DAMP, and methoctramine. Oxybutynin and propiverine suppress ATP-induced bladder overactivity other than through antimuscarinic mechanisms.

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.

Comparison of receptor binding characteristics of commonly used muscarinic antagonists in human bladder detrusor and mucosa

Recent studies have described muscarinic receptors on the mucosa and the detrusor of the human urinary bladder. Muscarinic receptor antagonists are effective in the treatment of overactive bladder (OAB), but their site(s) of action and actual therapeutic target are unclear. Our aim was to compare, in human bladder mucosa and detrusor, the radioligand binding characteristics of newer, clinically effective agents: darifenacin, its hydroxylated metabolite UK-148,993, fesoterodine, solifenacin, tolterodine, and trospium. Specimens were collected from asymptomatic patients (50-72 years old) undergoing open bladder surgery. Radioligand binding studies with the muscarinic antagonist [3H]quinuclidinyl benzilate (QNB) were performed separately on detrusor and mucosal membranes. All antagonists displayed high affinity when competing for [3H]QNB binding in both detrusor and mucosa. Inhibition constants were also obtained for all antagonists against individual muscarinic receptor subtypes expressed in Chinese hamster ovary cells. Here, fesoterodine showed anomalous binding results, suggesting that some conversion to its metabolite had occurred. Global nonlinear regression analysis of bladder binding data with five antagonists demonstrated 82% low-affinity sites in mucosa and 78% low-affinity sites in detrusor, probably representing M(2)/M(4) receptors. There was an excellent correlation (r(2) = 0.99) of low-affinity global estimates between detrusor and mucosa, whereas the corresponding high-affinity estimates ( approximately 20% of sites) were dissimilar. In conclusion, commonly used and clinically effective muscarinic receptor antagonists bind to receptors located on the bladder mucosa and the detrusor, providing support for the hypothesis that muscarinic receptors in the mucosa may represent an important site of action for these agents in OAB.

Intravesical oxybutynin for children with poorly compliant neurogenic bladder: a systematic review

PURPOSE

Children with neurogenic bladder and poor bladder compliance are usually treated with bladder catheterization and oral anticholinergic medication. They may become nonresponders to the drug or present with severe side effects. We evaluated the effectiveness and tolerability of intravesical oxybutynin in children with poorly compliant neurogenic bladder.

MATERIALS AND METHODS

We conducted a search of MEDLINE, EMBASE, CINAHL, SciELO, dissertations/theses in ProQuest, LILACS, the Cochrane Library, protocol registries and the gray literature. Two reviewers independently assessed study quality and extracted data.

RESULTS

Eight studies (2 prospective, 6 retrospective) assessed the effectiveness and side effects of intravesical oxybutynin in children with neurogenic bladder. A total of 297 children started treatment, of whom 22% (66 patients) discontinued therapy, with 9% (28) quitting due to systemic side effects. Mean change in bladder compliance (primary outcome) was reported in only 2 studies (+7.4 and +7.5 ml/cm H(2)O). The pooled mean change in pressure at maximum bladder capacity was -16.4 cm H(2)O (95% CI -22.8 to -10.0). Incontinence improved significantly in most studies, with "dry and improved" rates ranging from 61% to 83%. The funnel plot of pressure at maximum bladder capacity suggested no publication bias.

CONCLUSIONS

Adjunctive intravesical oxybutynin therapy increased mean maximum bladder capacity and decreased bladder pressure in children with neurogenic bladder. However, identified studies offered a low level of evidence, with most being poorly reported retrospective case series with potential biases. Although the incidence of side effects was lower with the intravesical route, side effects are still possible and should be discussed with patients and families. The evidence available is insufficient to recommend this therapy. Research of more sound study design such as a randomized controlled trial should be conducted to assess the efficacy and side effects of intravesical oxybutynin in children.

The sensory bladder (1): An update on the different sensations described in the lower urinary tract and the physiological mechanisms behind them

AIMS

To give an update of the actual information on sensory function in the lower urinary tract (LUT).

METHODS

We give an up-to-date review of the most modern and reasonable approach to the topic of physiological mechanisms involved in LUT sensory function and different sensations described in the LUT.

RESULTS

Although the sensory function of the LUT is a main player in the function of continence and micturition, it has been dealt with rather superficially for many decades. More recently the interest in this function grows and does so rapidly, both in basic as in clinical research. Sensation depends on neurophysiologic mechanisms in several different nerves, receptors, and transmitters. This knowledge creates a better understanding of sensory symptoms. Different stimuli can elicit sensations in the LUT such as bladder filling, micturition, noxious stimuli, external stimuli.

CONCLUSION

Sensation is the prerequisite of conscious bladder control and deserves full attention in the management of LUT dysfunction.

The neurogenic bladder: medical treatment

Neurogenic bladder sphincter dysfunction (NBSD) can cause severe and irreversible renal damage and bladder-wall destruction years before incontinence becomes an issue. Therefore, the first step in adequate management is to recognize early the bladder at risk for upper- and lower-tract deterioration and to start adequate medical treatment proactively. Clean intermittent catheterization combined with anticholinergics (oral or intravesical) is the standard therapy for NBSD. Early institution of such treatment can prevent both renal damage and secondary bladder-wall changes, thereby potentially improving long-term outcomes. In children with severe side effects or with insufficient suppression of detrusor overactivity despite maximal dosage of oral oxybutynin, intravesical instillation is an effective alternative. Intravesical instillation eliminates systemic side effects by reducing the first-pass metabolism and, compared with oral oxybutynin, intravesical oxybutynin is a more potent and long-acting detrusor suppressor. There is growing evidence that with early adequate treatment, kidneys are saved and normal bladder growth can be achieved in children so they will no longer need surgical bladder augmentation to achieve safe urinary continence in adolescence and adulthood.

The effects of tolterodine on bladder-filling sensations and perception thresholds to intravesical electrical stimulation: method and initial results

OBJECTIVES

To study the effects of the antimuscarinic agent tolterodine on the perception thresholds to intravesical electrical stimulation (IES) and the effects of the drug on subjective bladder sensation during normal filling cystometry in healthy female volunteers.

SUBJECTS AND METHODS

In seven healthy women IES was applied at 2.5 Hz (pulse width 10 ms, protocol 1), 2.5 Hz (pulse width 0.2 ms, protocol 2), and 250 Hz (pulse width 0.2 ms, protocol 3). Sensory perception thresholds were obtained using electric currents in 0.5 mA steps. Afterwards the bladder was filled and the first bladder-filling sensation, first desire to void, strong desire to void and urge to void were recorded. The bladder was then emptied, the volume measured and subjects were checked for residual urine by ultrasonography. The subjects then received 4 mg of tolterodine and the entire protocol was repeated 2 h afterward. The perception thresholds for IES and bladder sensation levels obtained at baseline were compared statistically with the corresponding values after tolterodine.

RESULTS

Tolterodine significantly increased perception thresholds to IES for all three protocols (P = 0.027, 0.018 and 0.018, respectively). The drug had no effect on the filling levels for the corresponding bladder sensation.

CONCLUSION

Oral tolterodine significantly increased the perception threshold to IES in healthy women; there was no effect on subjective bladder sensations during cystometry.

Effects of the M3 Receptor Selective Muscarinic Antagonist Darifenacin on Bladder Afferent Activity of the Rat Pelvic Nerve

OBJECTIVE

Previous studies have revealed that intravesical and systemic administration of oxybutinin suppress pelvic afferent nerves. This study evaluates the efficacy of a selective M3 antimuscarinic, darifenacin, on bladder afferent activity.

METHODS

Sixteen single bladder afferent fibers were isolated in nine female Sprague-Dawley rats. On the basis of their conduction velocities, they were grouped as Adelta or C fibers. The effect of repeat bladder filling was studied on the mechanosensitive properties of these units. The M3 receptor selective muscarinic antagonist darifenacin (0.1mg/kg) was administered intravenously. Unitary afferent activity was again analyzed 30, 60, 90, and 120 min after the drug administration.

RESULTS

Seven units corresponded to criteria for Adelta fibers, nine for C fibers. Repeat bladder filling did not change nerve activity in Adelta or C fibers. When nerve activity was expressed as a percent of control activity, afferent sensitivity changed after darifenacin in Adelta fibers: 86+/-27%, 30 min (p>0.05), 69 +/- 32%, 60 min (p<0.05), 56 +/- 36%, 90 min (p<0.05), and 61+/- 49%, 120 min (p>0.05), and in C fibers: 70+/-39%, 30 min (p<0.05), 57 +/- 49%, 60 min (p<0.05), 45 +/- 42%, 90 min (p<0.01), and 47 +/- 43%, 120 min (p<0.01).

CONCLUSIONS

In this study we show that darifenacin reduces bladder afferent activity in both Adelta and C fibers. The decrease in afferent spikes in C fibers may be more pronounced than that in Adelta fibers. These results may explain that the efficacy of darifenacin in overactive bladder symptoms is partly due to bladder afferent desensitization.