Pharmacological characterization of a novel investigational antimuscarinic drug, fesoterodine, in vitro and in vivo

Inhibition of voltage-dependent K+ channels by antimuscarinic drug fesoterodine in coronary arterial smooth muscle cells

Fesoterodine, an antimuscarinic drug, is widely used to treat overactive bladder syndrome. However, there is little information about its effects on vascular K⁺ channels. In this study, voltage-dependent K⁺ (Kv) channel inhibition by fesoterodine was investigated using the patch-clamp technique in rabbit coronary artery. In whole-cell patches, the addition of fesoterodine to the bath inhibited the Kv currents in a concentration-dependent manner, with an IC₅₀ value of 3.19 ± 0.91 μM and a Hill coefficient of 0.56 ± 0.03. Although the drug did not alter the voltage-dependence of steady-state activation, it shifted the steady-state inactivation curve to a more negative potential, suggesting that fesoterodine affects the voltage-sensor of the Kv channel. Inhibition by fesoterodine was significantly enhanced by repetitive train pulses (1 or 2 Hz). Furthermore, it significantly increased the recovery time constant from inactivation, suggesting that the Kv channel inhibition by fesoterodine is use (state)-dependent. Its inhibitory effect disappeared by pretreatment with a Kv 1.5 inhibitor. However, pretreatment with Kv2.1 or Kv7 inhibitors did not affect the inhibitory effects on Kv channels. Based on these results, we conclude that fesoterodine inhibits vascular Kv channels (mainly the Kv1.5 subtype) in a concentration- and use (state)-dependent manner, independent of muscarinic receptor antagonism.

Current pharmacotherapy of overactive bladder

Overactive bladder is a symptom complex consisting of bothersome storage urinary symptoms that is highly prevalent among both sexes and has a significant impact on quality of life. Various antimuscarinic agents and the beta-3 agonists mirabegron and vibegron are currently available for the treatment of OAB. Each drug has specific pharmacologic properties, dosing schedule and tolerability profile, making it essential to individualize the medical treatment for the patient's characteristics and expectations. In this manuscript, we review the most important factors involved in the contemporary pharmacological treatment of OAB.

Choosing the Most Efficacious and Safe Oral Treatment for Idiopathic Overactive Bladder: A Systematic Review and Network Meta-analysis

CONTEXT

The choice of the most efficacious drug for patients with idiopathic overactive bladder (IOAB) remains challenging.

OBJECTIVE

The aim of this network meta-analysis was to determine the most efficacious oral antimuscarinic or β-adrenoceptor agonist accounting for adverse events for the management of IOAB.

EVIDENCE ACQUISITION

A comprehensive electronic search was done in MEDLINE, EMBASE, Cochrane Central Register of Controlled Trials (CENTRAL), PubMed, and Ovid for studies in any language in February 2021 considering the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) statement. We included all randomized controlled trials assessing oral antimuscarinics or β-adrenoceptor agonists for the treatment of IOAB. We determined the effect of specific bothersome symptoms separately.

EVIDENCE SYNTHESIS

Fifty-four articles were included in our analysis. The most efficacious agents considering the evaluated outcomes were oxybutynin 15 mg/d in reducing incontinence episodes, imidafenacin 0.5 mg/d together with solifenacin 10 and 5 mg/d in reducing micturition episodes, fesoterodine 4 and 8 mg/d as well as solifenacin 10 mg/d in reducing urgency episodes, imidafenacin 0.5 mg/d and solifenacin 10 mg/d in reducing urgency urinary incontinence episodes, and solifenacin 10 mg/d, vibegron 50 mg/d, and fesoterodine 8 mg/d in improving the voided volume. Gastrointestinal problems, especially due to antimuscarinic agents, were the most prevalent adverse events.

CONCLUSIONS

Taken together, there is only minimal difference between the efficacy of oral antimuscarinics and that of β-adrenoceptor agonists. Although finding the best medication for all is impossible, finding the best treatment for every individual patient can be done by considering the efficacy of a medicine for the most bothersome symptom(s) in balance with drug-specific adverse events.

PATIENT SUMMARY

This study aimed to find the most efficient oral medication to treat overactive bladder, taking into consideration the adverse events. Based on our study, there is a minimal difference in the efficacy between the two major drug classes used to treat overactive bladder. Gastrointestinal problems were the most common adverse events in medical treatment of overactive bladder. Selection of the best treatment is possible through shared decision-making between the doctor and the patient based on the patient's most bothersome symptom. We provide a framework for physicians to facilitate shared decision-making with each individual patient.

Comparison of static and dynamic mode in the electrochemical oxidation of fesoterodine with the use of experimental design approach

Electrochemical conversion of fesoterodine to one of its oxidation products was evaluated with the application of the wall-jet flow cell. A traditional, "static" mode of electrolysis was compared with the "dynamic" mode of cell performance. For statistical assessment of the data, experiments were planned and performed with the application of design of experiments approach, namely Taguchi L18 design. After screening phase, the experimental settings were broadened or adjusted according to the results and optimization was performed. All of the samples were electrolysed with the use of chronoamperometric method in a three electrode system. The electrolysed samples were analysed using UHPLC-PDA-QDA method. The chromatographic run was performed in gradient elution with the application of C8 column. The response was expressed as % area of the main peak found with the PDA detection method whereas QDA detector was used in positive SIM mode for structural confirmation. All data obtained for both screening and optimization were treated together and linear models were adjusted. The use of large-surface glassy carbon electrode along with pH~7 were found to be the most significant factors influencing electrochemical oxidation of fesoterodine in both modes. The major differences were identified in terms of voltage applied to the electrodes which yielded the highest amounts of oxidation product. Evolution of electrochemical methods may serve as complementary technique in stress degradation studies in pharmaceutical industry.

The clinical pharmacology of the medical treatment for overactive bladder in adults

INTRODUCTION

Overactive bladder is a prevalent symptom complex that affects the patient's quality of life. Any disruption between the neuronal micturition pathway can lead to bladder overactivity. Neurogenic causes, myogenic causes, aging, bladder outlet obstruction, sex, and psychological factors are some of the factors contributing to bladder overactivity. The complaint of any symptoms of OAB, which is highly prevalent and affects overall QOL, often needs therapeutic interventions. When conservative therapy methods fail, the addition of medications is recommended. The most commonly used agents for the treatment of OAB are antimuscarinic drugs. New classes of drugs, such as beta-3 agonists, have enriched our pharmacologic armamentarium.

AREAS COVERED

In this review, with a special focus on oral pharmacological treatments, we discussed the definition, etiology, symptoms, diagnosis, and management of OAB.

EXPERT OPINION

OAB is a multifactorial condition with every patient presenting with a different collection of symptoms and signs. Medical therapies should be given in conjunction with behavioral therapies. Using high or low doses, flexible doses, and stopping or changing the medications are interchangeable strategies based on the level of treatment efficacy and patient satisfaction.

Direct in vitro and in vivo demonstration of muscarinic receptor binding by the novel radioligand, [3H]5-hydroxymethyltolterodine, in the bladder and other tissues of rats

In vitro and in vivo binding sites of [³H]-labeled 5-hydroxymethyltolterodine (5-HMT), a new radioligand for labeling muscarinic receptors in rat tissues were characterized. Specific [³H]5-HMT binding in rat tissues was saturable and of high affinity in each tissue. The dissociation constant (K_d) was significantly lower in bladder and heart than in submaxillary gland. Significant levels of in vivo specific [³H]5-HMT binding by intravenous injection of the radioligand were detected in tissues, except for cerebral cortex. Thus, [³H]5-HMT was shown to specifically label muscarinic receptors in rat tissues, suggesting a useful radioligand for labeling muscarinic receptors with high affinity.

Effects of combined treatment with fesoterodine and mirabegron in a pelvic congestion rat model: Results from in vitro and in vivo functional studies

Objectives

To examine the effect of combining a nonselective muscarinic receptor antagonist, 5‐hydroxymethyl tolterodine (an active metabolite of fesoterodine), with a β3 adrenoceptor agonist, mirabegron, in a rat model of pelvic congestion.

Methods

The rat pelvic congestion model used female Sprague‐Dawley rats with their bilateral common iliac and uterine veins ligated. Expressions of M2 and M3 receptor subtypes in the urothelium and detrusor were detected by real‐time polymerase chain reaction assays. The effects of both drugs were investigated on isolated bladder strips contracted by electrical field stimulation. in vivo single cystometry was used to assess the effects of 5‐hydroxymethyl tolterodine and mirabegron independently or in combination on bladder capacity, micturition pressure, and threshold pressure.

Results

Pelvic congestion rats showed decreased bladder capacity compared with controls, but micturition pressure and threshold pressure were unchanged. Pelvic congestion model rats also demonstrated an approximately two‐fold increase in expression of both M2 and M3 receptor subtypes in the urothelium. Additive relaxant effects of 5‐hydroxymethyl tolterodine and mirabegron were observed in vitro in the electrical field stimulation‐induced contractions of bladder strips from pelvic congestion rats. In vivo, bladder capacity was increased significantly by a combination of 5‐hydroxymethyl tolterodine and mirabegron, with the combined effect exceeding the sum of the effects of monotherapies. Micturition pressure and threshold pressure did not significantly differ between groups.

Conclusions

The combination of 5‐hydroxymethyl tolterodine with mirabegron suggests the potential of synergistic effects in a rat pelvic congestion model.

Muscarinic receptor binding of fesoterodine, 5-hydroxymethyl tolterodine, and tolterodine in rat tissues after the oral, intravenous, or intravesical administration

The present study aimed to characterize muscarinic receptor binding of fesoterodine, 5-hydroxymethyl tolterodine (5-HMT), and tolterodine in bladder and other tissues of rats after their oral, intravenous, or intravesical administration. Muscarinic receptors in tissues were measured by using [N-methyl-³H]scopolamine methyl chloride ([³H]NMS). The in vitro binding affinity for muscarinic receptors was the highest by 5-HMT, followed by tolterodine and fesoterodine. Fesoterodine exhibited lower affinity in rat submaxillary gland than in detrusor muscle and urothelium. Muscarinic binding affinities of 5-HMT and tolterodine were similar among tissues. The duration of binding of oral fesoterodine to muscarinic receptors was longer in bladder than in submaxillary gland, heart, and lung, and its binding was little observed in colon and cerebral cortex. Binding activity of intravenous 5-HMT to muscarinic receptors was significantly observed in all tissues, except cerebral cortex, with a longer duration in bladder. Significant binding of bladder detrusor and urothelial muscarinic receptors was observed following intravesical instillation of 5-HMT. This selectivity may be attributed to the direct blockade of bladder receptors by excreted urinary 5-HMT. Thus, fesoterodine may be efficacious as a treatment for patients with overactive bladder.

Basic and clinical aspects of antimuscarinic agents used to treat overactive bladder

Antimuscarinic agents are now widely used as the pharmacological therapy for overactive bladder (OAB) because neuronal (parasympathetic nerve) and non-neuronal acetylcholine play a significant role for the bladder function. In this review, we will highlight basic and clinical aspects of eight antimuscarinic agents (oxybutynin, propiverine, tolterodine, solifenacin, darifenacin, trospium, imidafenacin, and fesoterodine) clinically used to treat urinary dysfunction in patients with OAB. The basic pharmacological characteristics of these eight antimuscarinic agents include muscarinic receptor subtype selectivity, functional bladder selectivity, and muscarinic receptor binding in the bladder and other tissues. The measurement of drug-receptor binding after oral administration of these agents allows for clearer understanding of bladder selectivity by the integration of pharmacodynamics and pharmacokinetics under in vivo conditions. Their central nervous system (CNS) penetration potentials are also discussed in terms of the feasibility of impairments in memory and cognitive function in elderly patients with OAB. The clinical aspects of efficacy focus on improvements in the daytime urinary frequency, nocturia, bladder capacity, the frequency of urgency, severity of urgency, number of incontinence episodes, OAB symptom score, and quality of life (QOL) score by antimuscarinic agents in patients with OAB. The safety of and adverse events caused by treatments with antimuscarinic agents such as dry mouth, constipation, blurred vision, erythema, fatigue, increased sweating, urinary retention, and CNS adverse events are discussed. A dose-dependent relationship was observed with adverse events, because the risk ratio generally increased with elevations in the drug dose of antimuscarinic agents. Side effect profiles may be additive to or contraindicated by other medications.

Urinary incontinence in men: current and developing therapy options

INTRODUCTION

Urinary incontinence in men is a significant and often underappreciated problem. Men can have urgency and or stress incontinence. Urgency incontinence as part of the overactive bladder (OAB) syndrome and can often coexist with benign prostatic obstruction (BPO) in men and the initial treatment of this is conservative lifestyle changes and then medical therapy.

AREAS COVERED

This literature review aims to cover synthetic drugs currently utilised to treat urinary incontinence in men that are phase III and onwards. Neurological incontinence and surgical treatment options for male urinary incontinence are beyond the scope of this review.

EXPERT OPINION

The most common form of urinary incontinence in men is urgency incontinence secondary to an OAB, which often co-exists in men, with bladder outflow obstruction (BOO). The pharmacotherapy options to treat OAB include antimuscarinics, β3 agonists and phosphodiesterase inhibitors. Antimuscarinics and β3 agonists are effective in treating OAB, and have been found to have no increased urinary retention risk in the group of patients with co-existing BPO. Emerging medications include the alternative β3 agonists - solabegron and ritobegron. The future may include novel combinations of these therapies.

Expression of brain derived-neurotrophic factor and granulocyte-colony stimulating factor in the urothelium: relation with voiding function

BACKGROUND

We designed this experiment to elucidate the relationship between the expression of brain derived-neurotrophic factor (BDNF), the expression of granulocyte-colony stimulating factor (G-CSF), and the development of overactive bladder (OAB). In our previous study, the urothelium was observed to be more than a simple mechanosensory receptor and was found to be a potential therapeutic target for OAB. Moreover, neuregulin-1 and BDNF were found to be potential new biomarkers of OAB. Here, we investigated the relationship between changes in the voiding pattern and the expression of BDNF and G-CSF in the urothelium and evaluated the effects of 5-hydroxymethyl tolterodine (5-HMT) on rats with bladder outlet obstruction (BOO).

METHODS

A total of 100 Sprague-Dawley rats were divided into the following groups: 20 control rats; 40 BOO rats; and 40 BOO rats administered 5-HMT (0.1 mg/kg). After BOO was induced for 4 weeks, the rats were assessed by cystometrography. The changes in BDNF and G-CSF expression were examined in both separated urothelial tissues and in cultured urothelial cells by reverse transcription polymerase chain reaction (RT-PCR).

RESULTS

BOO rats showed increased non-voiding activity [NVA; (number/10 voidings)] and bladder weight and decreased micturition volume (MV), micturition interval (MI), and micturition time (MT) relative to the controls. Moreover, the 5-HMT administration rats showed decreased NVA and bladder weight and increased MV and MI in comparison to the BOO rats. BDNF and G-CSF expression was increased in BOO rats and decreased following 5-HMT administration. In this model, voiding dysfunction developed as a result of BOO. As a therapeutic agent for OAB, the administration of 5-HMT improved the voiding dysfunction.

CONCLUSIONS

BDNF and G-CSF might modulate voiding patterns through micturition pathways and might be involved only in the urothelium. Moreover, the expression of both genes in the urothelium might be related to voiding dysfunction in OAB patients. Thus, the urothelium has an important role in the manifestation of voiding symptoms.

Phase II drugs that target cholinergic receptors for the treatment of overactive bladder

INTRODUCTION

Overactive bladder (OAB) is a term used to describe the symptom syndrome of urgency, with or without urgency incontinence, usually associated with frequency and nocturia. Antimuscarinics are the most widely prescribed class of drugs for OAB, although their systemic adverse effects limit their use in clinical practice as compliance. This has led to developments in the field.

AREAS COVERED

In this review, the authors describe Phase II drugs that target cholinergic receptors. First, the authors present the new antimuscarinics (tarafenacin and afacifenacin). This is followed by reports on a combination drug (tolenix) containing a muscarinic antagonist (tolterodine) associated with a muscarinic agonist (pilocarpine). Further, the authors discuss the trials of well-known drugs in either new combination therapy (solifenacin and mirabegron) or with new routes of delivery (oxybutynin vaginal ring). Finally, the authors examine the option of targeting nicotinic acetylcholine receptors (dexmecamylamine).

EXPERT OPINION

Different strategies have been adopted to improve the efficacy and tolerability of therapeutics for OAB. Nicotinic receptors represent a novel therapeutic target; however, it is unlikely that antimuscarinic agents will be replaced as standard first-line therapy in the near future.

Rationale for the use of anticholinergic agents in overactive bladder with regard to central nervous system and cardiovascular system side effects

PURPOSE

Central nervous system (CNS) and cardiovascular system (CVS) side effects of anticholinergic agents used to treat overactive bladder (OAB) are underreported. Hence, this review aimed to focus on the mechanisms of CNS and CVS side effects of anticholinergic drugs used in OAB treatment, which may help urologists in planning the rationale for OAB treatment.

MATERIALS AND METHODS

PubMed/MEDLINE was searched for the key words "OAB," "anticholinergics," "muscarinic receptor selectivity," "blood-brain barrier," "CNS," and "CVS side effects." Additional relevant literature was determined by examining the reference lists of articles identified through the search.

RESULTS

CNS and CVS side effects, pharmacodynamic and pharmacokinetic properties, the metabolism of these drugs, and the clinical implications for their use in OAB are presented and discussed in this review.

CONCLUSIONS

Trospium, 5-hydroxymethyl tolterodine, darifenacin, and solifenacin seem to have favorable pharmacodynamic and pharmacokinetic properties with regard to CNS side effects, whereas the pharmacodynamic features of darifenacin, solifenacin, and oxybutynin appear to have an advantage over the other anticholinergic agents (tolterodine, fesoterodine, propiverine, and trospium) with regard to CVS side effects. To determine the real-life situation, head-to-head studies focusing especially on CNS and CVS side effects of OAB anticholinergic agents are urgently needed.

Evaluation of fesoterodine fumarate for the treatment of an overactive bladder

INTRODUCTION

Fesoterodine fumarate is an approved drug for overactive bladder. The aim of this study is to review the preclinical and most up to date clinical data on fesoterodine, with a special emphasis on its unique pharmacokinetic features and its implications on safety and tolerability in various patient populations.

AREAS COVERED

In this review, the authors extensively reviewed available literature via PubMed search regarding fesoterodine, covering its mechanism of action, pharmacodynamics and pharmacokinetics, clinical efficacy, safety, and tolerability.

EXPERT OPINION

Fesoterodine is an anti-muscarinic agent with a unique pharmacokinetic profile. It is a prodrug that is rapidly metabolized to its active form by nonspecific plasma esterases. Its metabolism is independent of the cytochrome P450 enzyme system. This along with its dual excretion pathways and minimal central nervous system penetration leads to less variability in drug exposure and allowance of administration in those with mild to moderate renal and hepatic insufficiency and in the geriatric population.

Changes of neuregulin-1 (NRG-1) expression in a rat model of overactive bladder induced by partial urethral obstruction: is NRG-1 a new biomarker of overactive bladder?

Background

To determine whether neuregulin-1(NRG-1) is a potential new biomarker of overactive bladder (OAB) induced by partial urethral obstruction in a rat model of OAB and to evaluate the urothelium as a therapeutic target of OAB.

Methods

Female Sprague–Dawley rats were separated into three 20-animal groups: normal, OAB, and 5-hydroxymethyl tolterodine (5-HMT)-treated OAB. In the OAB and OAB + 5-HMT groups, the urethra of each animal was partially obstructed; the OAB + 5-HMT group received intravenous 5-HMT for 3 weeks. At the conclusion of the 5-HMT dosing, the rats in each group underwent cystometrography, and the bladders were histologically evaluated. The expression of brain derived-neurotrophic factor (BDNF) and NRG-1 were evaluated in the urothelium.

Results

Compared with the control group, the OAB group showed a markedly increased bladder weight and a significant decrease in the micturition interval and volume; rats in the OAB + 5-HMT group showed decreased bladder weights and an improved micturition interval and volume. BDNF and NRG-1 were expressed at significantly higher levels in the OAB group, and were significantly reduced in the OAB + 5-HMT group compared with the control group.

Conclusions

The study suggests that NRG-1 is a potential new biomarker of OAB; the urothelium might be a therapeutic target for OAB treatment.

Fesoterodine, its active metabolite, and tolterodine bind selectively to muscarinic receptors in human bladder mucosa and detrusor muscle

OBJECTIVE

To comparatively characterize the binding activity of fesoterodine, its active metabolite (5-hydroxymethyl tolterodine [5-HMT]), and tolterodine in the human bladder mucosa, detrusor muscle, and parotid gland.

MATERIALS AND METHODS

Muscarinic receptors in the homogenates of human bladder mucosa, detrusor muscle, and parotid gland were measured by a radioligand binding assay using [N-methyl-(3)H] scopolamine methyl chloride.

RESULTS

Fesoterodine, 5-HMT, and tolterodine competed with [N-methyl-(3)H] scopolamine methyl chloride for binding sites in the bladder mucosa, detrusor muscle, and parotid gland in a concentration-dependent manner. The affinity for muscarinic receptors of these agents was significantly greater in the bladder than in the parotid gland, suggesting pharmacologic selectivity for the bladder over the parotid gland. The bladder selectivity was larger for fesoterodine and 5-HMT than for tolterodine. Fesoterodine, 5-HMT, and tolterodine resulted in significantly increased (two- to five-fold) values of the apparent dissociation constant for specific [N-methyl-(3)H] scopolamine methyl chloride binding in the detrusor muscle and parotid gland, with little effect on the corresponding values of the maximal number of binding sites. This finding indicates that these agents bind to the human muscarinic receptors in a competitive and reversible manner.

CONCLUSION

Fesoterodine and 5-HMT bind to the muscarinic receptors with greater affinity in the human bladder mucosa and detrusor muscle than in the parotid gland in a competitive and reversible manner.

Pharmacokinetics and toxicity of antimuscarinic drugs for overactive bladder treatment in females

INTRODUCTION

Antimuscarinics (AMs) are the mainstay of pharmacological treatment of overactive bladder (OAB), a symptom complex defined by the presence of urinary urgency, usually associated with frequency and nocturia, with or without urgency urinary incontinence. The AMs used to treat OAB differ in their pharmacological profiles, which may affect their potential for causing adverse effects (AEs).

AREAS COVERED

The present article aims to review the literature about pharmacokinetics (PK) of the different AMs used in the treatment of OAB. Furthermore, the AEs related to the use of these drugs and their incidence are presented. This systematic review is based on material searched and obtained via Medline, Pubmed and EMBASE up to March 2012 using the search terms "adverse events, pharmacokinetics, tolerability" in combination with "darifenacin, fesoterodine, imidafenacin, oxybutynin, propiverine, solifenacin, tolterodine, and trospium."

EXPERT OPINION

Antimuscarinics are the first-line pharmacological treatment for OAB. Despite the development of new molecules that improve their efficacy/safety profile, there are some drugs that are pharmacokinetically more appropriate to be prescribed in specific populations such as patients with neurological disease or the elderly. Moreover, research should be encouraged in evaluating antimuscarinics in conjunction with other drugs such as estrogens or beta-agonists. The identification of prognostic criteria for pharmacological therapy would be helpful.

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.

Voltage-gated Na+ channel blockers reduce functional bladder capacity in the conscious spontaneously hypertensive rat

OBJECTIVE

To evaluate the consequence of pharmacologic inhibition of voltage-gated Na(+) channels (Nav) in the conscious rat, based on Nav having been implicated as modulators of rodent urodynamics using knockout as well as antisense oligodeoxynucleotide approaches.

METHODS

The urodynamic response to standard Nav blockers, lamotrigine, amitriptyline, mexiletine, and carbamazepine were evaluated using conscious, continuous-filling cystometry in spontaneously hypertensive rats (SHRs). As a selectivity evaluation, the activity of the Nav blockers at muscarinic receptors was assessed via effect on carbachol-evoked bladder contractions.

RESULTS

Lamotrigine, amitriptyline, mexiletine, and carbamazepine decreased peak micturition pressure, micturition interval, and void volume. These effects were markedly similar to observations with muscarinic antagonists. Therefore, we evaluated the selectivity of these agents against bladder muscarinic receptors. Lamotrigine, mexiletine, and carbamazepine had no effect on muscarinic bladder contractions, whereas amitriptyline displayed a robust antagonism of carbachol-induced contractility.

CONCLUSION

Three Nav blockers--lamotrigine, mexiletine, and carbamazepine--demonstrated a reduction in micturition pressure and functional bladder capacity, similar to previous observations with muscarinic antagonists. These 3 Nav blockers are free of muscarinic antagonism, consistent with their cystometric effects being mediated via their Nav blocking activities. The negative findings reported here with Nav blockers suggest that Nav channel blockade is unlikely to reflect an improved treatment strategy for bladder disorders over currently prescribed muscarinic antagonists.

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.

Antimuscarinics for the treatment of overactive bladder: understanding the role of muscarinic subtype selectivity

INTRODUCTION AND HYPOTHESIS

Antimuscarinic agents appear to exert their therapeutic activity in overactive bladder (OAB) via blockade of the M(3) muscarinic receptor subtype. Antimuscarinics are broadly similar in efficacy, but their safety and tolerability profiles vary, which may reflect differences in muscarinic receptor selectivity profiles.

METHODS

This review of available literature aims to determine whether antimuscarinic agents with greater M(3) selectivity have clinical advantages over less selective drugs.

RESULTS

Antimuscarinic agents differ widely in their propensity to cause cognitive and cardiovascular (CV) effects, which appear mainly to be related to differences in their relative selectivity for binding to non-M(3) receptors, including M(1) receptors in the brain and cardiac M(2) receptors.

CONCLUSIONS

Cognitive and CV effects are especially pertinent for the OAB patient who tends to be older with various comorbidities and is often taking multiple medications. Hence, it is important to consider the risk/benefit balance of antimuscarinic agents when selecting OAB treatment.

Anticholinergics for overactive bladder therapy: central nervous system effects

The mainstay of pharmacological treatment of overactive bladder (OAB) is anticholinergic therapy using muscarinic receptor antagonists (tertiary or quaternary amines). Muscarinic receptors in the brain play an important role in cognitive function, and there is growing awareness that antimuscarinic OAB drugs may have adverse central nervous system (CNS) effects, ranging from headache to cognitive impairment and episodes of psychosis. This review discusses the physicochemical and pharmacokinetic properties of OAB antimuscarinics that affect their propensity to cause adverse CNS effects, as observed in phase III clinical trials and in specific investigations on cognitive function and sleep architecture. PubMed/MEDLINE was searched for "OAB" plus "muscarinic antagonists" or "anticholinergic drug." Additional relevant literature was identified by examining the reference lists of papers identified through the search. Preclinical and clinical trials in adults were assessed, focusing on the OAB antimuscarinics approved in the United States. The blood-brain barrier (BBB) plays a key role in protecting the CNS, but it is penetrable. The lipophilic tertiary amines, particularly oxybutynin, are more likely to cross the BBB than the hydrophilic quaternary amine trospium chloride, for which there are very few reports of adverse CNS effects. In fact, in 2008 the US product labels for oral oxybutynin were modified to include the potential for anticholinergic CNS events and a warning to monitor patients for adverse CNS effects. Even modest cognitive impairment in the elderly may negatively affect independence; therefore, selection of an antimuscarinic OAB drug with reduced potential for CNS effects is advisable.

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.

Non-motor extranigral signs and symptoms in Parkinson's disease

Clinical symptoms in Parkinson's disease (PD) comprise both motor and non-motor symptoms. In this disease, synucleinopathic-induced, nigral dopamine deficiency-related dysfunction of the basal ganglia is held responsible for the characteristic levodopa-responsive motor signs and symptoms (bradykinesia, hypokinesia, rigidity), known as parkinsonism and essential for clinical diagnosis in PD, as well as subtle motivational and cognitive dysfunctions. Some motor symptoms, such as tremor and postural instability, and most non-motor symptoms, however, are not fully levodopa-responsive, and suggested to manifest extranigral pathology. These symptoms include autonomic, sleep, sensory and neuropsychiatric symptoms, which in some cases may precede the first signs of motor parkinsonism, closely correlating with the progression of Lewy body pathology in PD. The recognition and treatment of these mostly under-recognized and under-treated symptoms is important, as these symptoms might have more impact on the quality of life in PD patients as compared to motor parkinsonism. On top of this, recognition of these manifestations in the prodromal phase of motor PD is critical to early diagnosis and treatment, as disease-modifying drugs, once identified, should be initiated as soon as possible, preferably in this premotor phase of the disease. On top of this, (non)motor extranigral symptoms in PD might also be of iatrogenic origin, whether directly as indirectly. During conventional, oral, dopaminomimetic treatment, the progressive loss of striatal dopaminergic nerve endings with the loss of cerebral dopamine storage capacity, renders the cerebral dopamine level fully dependent of the plasma levodopa levels, thus changing dopaminergic receptor stimulation from continuous to a more pulsatile pattern. Supposedly due to this process, neuroplastic changes in (sub)cortical dopaminergic pathways might cause therapeutic response fluctuations: motor and nonmotor fluctuations with anxiety- and panic-attacks and/or mood swings, dyskinesias and punding. Finally, dopaminomimetic pharmacotherapy may also induce extranigral non-motor drug-related direct adverse effects, such as impulse control disorders. In this article, non-motor signs and symptoms of extranigral PD-related pathology will be discussed, as well as the (suggested) criteria for diagnosis and treatment. Of course, also the recognition of the signs and symptoms of the prodromal (premotor) phase, suggestive for the presence of the PD, will be discussed. Iatrogenic non-motor symptoms, though, will not be further discussed.

Detrusor overactivity: an overview

Detrusor overactivity (DO) is a common clinical problem having profound effects on the quality of life (QOL) of women. With the use of meshes in the antiincontinence surgery, a new onset of DO, de novo DO has become an important issue in postoperative QOL of women. A systematic review of English language literature was conducted from Pubmed and publications of the last 7 years were analyzed and presented in this review. Multiple pathological events in the urothelium, sub-urothelium and possibly in the detrusor muscle seem to underlie the pathophysiology of DO. A variety of approaches, from life style modification to minimal-invasive surgery are available to treat DO and it is the responsibility of the physician to properly select and apply these modalities with the ultimate aim in improving the QOL of the patients. It is imperative to know the various pathophysiological processes that underlie the causation of DO to select proper management approach.

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.

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.

Fesoterodine

black triangle Fesoterodine is a muscarinic receptor antagonist that is rapidly and extensively converted to the active and more potent metabolite 5-hydroxymethyltolterodine. The drug is approved for once-daily oral administration in patients with overactive bladder syndrome (OAB). black triangle In two large, 12-week, randomized, double-blind, multicentre, phase III trials, oral fesoterodine 4 or 8 mg once daily improved the symptoms of OAB (frequency of micturition, urgency and urge incontinence) significantly more than placebo. black triangle Furthermore, significantly more patients receiving fesoterodine 4 or 8 mg once daily had a positive response to therapy than those receiving placebo, as determined by a treatment questionnaire. black triangle Health-related quality of life was improved to a significantly greater extent in patients with OAB who received fesoterodine 4 or 8 mg once daily than in those who received placebo in a post hoc analysis of pooled data from the phase III trials. black triangle Fesoterodine 4 or 8 mg once daily was generally well tolerated in patients with OAB; the most frequent adverse event was dry mouth, which was generally mild to moderate in severity.

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.

Emerging drugs for treatment of overactive bladder and detrusor overactivity

BACKGROUND

Overactive bladder (OAB) signifies the presence of urinary urgency and can have major effects on quality of life and social functioning. Standard antimuscarinic drugs have good initial response rates but substantial adverse effects and long-term compliance problems.

OBJECTIVES

To review the complexities of the mechanisms underlying OAB and the current drugs available for treating its symptoms.

METHODS

The literature was reviewed to define current therapies and drugs in clinical trials. Articles were identified by means of a computerised PubMed and Cochrane Library search (using the following keywords: overactive bladder, detrusor overactivity, urgency and bladder), supported by a search of the PharmaProjects database.

CONCLUSIONS

New drug classes, such as beta-3 adrenergic agonists, may work by reducing contractility or excitability of bladder muscle. Moderation of afferent activity may allow improved OAB symptoms, with lower risk of affecting voiding function. Agents acting on the CNS could influence OAB favourably, but target selection and adverse effects are an issue. The recognition of the functional contribution of the urothelium and the diversity of nerve transmitters has sparked interest in both peripheral and central modulation of OAB pathophysiology.