Pharmacotherapy of overactive bladder in adults: a review of efficacy, tolerability, and quality of life

Safety and Efficacy of Trospium Chloride and Solifenacin in Stroke-Induced Neurogenic Lower Urinary Tract Dysfunction: A Randomized Controlled Trial

BACKGROUND

Neurogenic dysfunction of the lower urinary tract is one of the challenging diseases with high burdens in urology. Our study aims to evaluate the efficacy of a 4-week treatment with Solifenacin and Trospium chloride and assess their safety and impact on quality of life.

METHODS

Following the selection of 206 stroke patients from two centers who met specific eligibility criteria, including a clinical diagnosis of stroke, normal cognitive function, and the presence of lower urinary tract symptoms (LUTS), participants were randomly assigned to receive oral Solifenacin, Trospium chloride, or a placebo. Under the supervision of the Ethics Committee, the baseline characteristics, compliance with medication, and outcomes were monitored, gathered, and analyzed.

RESULTS

The majority of participants were male, with a mean age of 67.3, and most had ischemic stroke. The groups had no significant difference in urinary symptoms after stroke. All of the symptoms in the study groups, according to the NBSS questionnaire, were decreased following treatment compared to the baseline (p < 0.05). After treatment, ICIQ-OAB, and ICIQ-LUTS-QOL total scores and bothersome scores decreased significantly compared to baseline (p < 0.001). When compared to the placebo, both Trospium chloride and Solifenacin alleviated symptoms according to the NBSS questionnaire and ICIQ-LUTS-QOL, total ICIQ-OAB, and the total score of ICIQ-OAB-Bothersome. However, the total LUTS-QOL-Bothersome score did not change in the active treatment groups compared to the placebo. While comparing the two drugs, these values were similar except for the total score of LUTS-QOL-Bothersome, ICIQ-OAB, and ICIQ-OAB-Bothersome in favor of the Solifenacin group. Moreover, Solifenacin had fewer side effects compared to Trospium chloride or placebo.

CONCLUSION

The study analyzed 206 stroke patients in two international centers and found both drug arms effective in treating overactive bladder. However, inconsistencies were found in efficacy and safety, necessitating further studies with larger populations.

TRIAL REGISTRATION

This triple-blind, multicenter, randomized controlled trial was done on 206 stroke patients after getting Ethical Committee approval and registering the project on IRCT (IRCT20160606028304N2).

A Comparative Study of Solifenacin, Mirabegron, and Their Combination as Bladder Relaxants in the Management of Overactive Bladder

Introduction  Overactive bladder (OAB) is a medical state that presents as the urgency of urine and increased frequency of micturition and is diagnosed on the basis of the presence of these symptoms in the absence of other explainable diagnoses. The management of this condition includes conservative management, medical management/pharmacotherapy, and surgical management. The overactive bladder has been treated with smooth muscle relaxants, but there are conflicting results. Hence, this study aimed to assess the result of the two smooth muscle relaxants, mirabegron and solifenacin, and their combination to manage an overactive bladder. Methodology  A clinical trial was conducted at Swaroop Rani Nehru Hospital, Motilal Nehru Medical College, Prayagraj, India, over the period from November 2019 to December 2020. Ninety patients with OAB were divided into three groups: G1, G2, and G3. These groups were administered solifenacin, mirabegron, and a combination of mirabegron and solifenacin (S+M), respectively. Follow-ups were conducted at 2, 4, 12, and 18 weeks for evaluation. Data were entered into IBM SPSS Statistics for Windows, Version 23 (Released 2015; IBM Corp., Armonk, New York, United States). Appropriate statistical tests, including the chi-square and ANOVA, were employed in this study. Observation  The combination of mirabegron and solifenacin was significantly more effective in terms of response compared to solifenacin alone. There was no significant difference between solifenacin versus mirabegron, or between mirabegron (M) and the combination of mirabegron (M) and solifenacin (S). Side effects were more severe in patients taking high doses of solifenacin. Conclusion  The S + M combination has higher efficacy than solifenacin and mirabegron when given alone.

Learning Curve of Botulinum Toxin Bladder Injection for the Treatment of Refractory Overactive Bladder

PURPOSE

Intradetrusor botulinum toxin injections is an established second-line treatment for patients with refractory overactive bladder syndrome (OAB). We aimed to evaluate the learning curve of intradetrusor injections with botulinum toxin for the treatment of refractory OAB.

PATIENTS AND METHODS

This retrospective study analyzed all women with idiopathic and refractory OAB who underwent botulinum toxin bladder injections performed by residents with no previous experience with operative cystoscopy under consultant supervision. Baseline International Consultation on Incontinence Questionnaire-Short Form questionnaire (ICIQ-SF) and Euroqol (EQ-5D) questionnaires were collected. Procedural data (operative time, number of valid injections, complications, subjective easiness, perceived tolerability) and patients' outcomes (Patients Global Impression of Improvement (PGI-I), ΔICIQ-SF, ΔEQ-5D, need for self intermittent catheterization, duration of efficacy) were considered as markers to evaluate learning curves for each resident.

RESULTS

Twenty-seven patients underwent intravesical injection of botulinum toxin performed by residents. Only a grade 1 Clavien-Dindo complication occurred, and none of the patients had urinary retention. PGI-I was very satisfactory, scoring 1.4 ± 0.9. Both ICIQ-SF and EQ-5D 2-2 were statistically improved (p < 0.00001 and p = 0.04, respectively). The mean duration of efficacy resulted to be 8.0±4.3 months. A positive effect of the learning curve was observed only for operative time, subjective easiness, and perceived tolerability.

CONCLUSION

Intradetrusor botulinum toxin injection for the treatment of refractory OAB is characterized by high efficacy and very low complications even at the very beginning of the learning curve when performed under proper mentorship.

Intravesical injection of onabotulinumtoxinA in neurogenic overactive bladder patients with human T-cell leukemia virus type 1-associated myelopathy: A single-institution case series

INTRODUCTION

Neurogenic overactive bladder is a main feature of human T-cell leukemia virus type 1-associated myelopathy/tropical spastic paraparesis. We successfully performed intravesical onabotulinumtoxinA therapy for refractory neurogenic overactive bladder due to human T-cell leukemia virus type 1-associated myelopathy/tropical spastic paraparesis.

CASE PRESENTATION

We retrospectively reviewed four neurogenic overactive bladder patients with human T-cell leukemia virus type 1-associated myelopathy/tropical spastic paraparesis who underwent bladder wall injections of onabotulinumtoxinA from April to October 2020. All patients were female. Their median age was 66 (range, 63-71) years. They were previously treated with β3-adrenergic receptor agonists or anticholinergic drugs alone or in combination for ≥12 weeks. However, insufficient results were obtained. After 4 weeks of intravesical onabotulinumtoxinA therapy, overactive bladder symptoms improved and maximum cystometric capacity increased in all cases.

CONCLUSION

Intravesical onabotulinumtoxinA therapy may be useful for treating refractory overactive bladder due to human T-cell leukemia virus type 1-associated myelopathy/tropical spastic paraparesis.

Trends and Clinical Practice Patterns of Sacral Neuromodulation for Overactive Bladder

OBJECTIVES

The aim of this study was to investigate surgical practice patterns of American urologists treating refractory overactive bladder (OAB) over the past decade. Refractory OAB remains a management challenge to urologists. When multiple medical therapies have failed, treatment options may include sacral neuromodulation (SNM) or surgery such as augmentation cystoplasty (AC).

METHODS

Data on SNM and AC performed between 2003 and 2012 by certifying and recertifying urologists were obtained in the form of annualized case logs from the American Board of Urology (ABU). Associations between surgeon characteristics (type of certification, annual volume, practice type, and location) and these procedures were evaluated.

RESULTS

Over the past decade, 756 of 6355 urologists certified with the ABU performed SNM or AC for the treatment of refractory OAB. Forty-five (6%) of these surgeons completed fellowships in female urology and 71 surgeons (9%) completed another type of fellowship program. Surgeons recertifying with ABU performed 76% of all SNM procedures. Although SNM and AC have increased from 64 to 2086 between 2003 and 2012, however, this is mainly driven by the increase of SNM from 48 to 2068 cases. Rates of AC have remained stable with 14 to 38 cases reported annually. However, they have declined relative to the total, from 25% in 2003 to less than 1% in 2012.

CONCLUSIONS

Sacral neuromodulation has increased dramatically over the past decade in surgeons certified with the ABU. This is in contrast to AC, which while remaining stable in number of procedures.

Comparison of Oxidative Effects of Two Different Administration Form of Oxybutynin in the Potential Target Tissues

Oxybutynin is an important anticholinergic agent that prevents uncontrolled contractions in the treatment of overactive bladder (OAB). However, drugs containing oxybutynin have significant side effects such as dry eyes, dry mouth, increased heart rate, constipation, blurred vision, and confusion. In recent years, new delivery methods for this agent are being searched. One of them is vaginal delivery. In this study, we aimed to compare the effects of oxybutynin on oxidative parameters in the potential target tissues of the oral and vaginal delivery. Female New Zealand white rabbits (n=12) were divided into two groups: oral delivery and vaginal delivery. The animals were sacrificed 48 h after administration and nitric oxide (NOx), thiobarbituric acid-reactive substances (TBARs), and glutathione (GSH) levels were determined spectrophotometrically in the aorta, salivary gland, and small intestine tissue samples. Vaginal delivery significantly decreased NOx levels in all tissue samples as compared to oral delivery (p < 0.05). Moreover, it reduced TBARs levels in salivary gland and aorta tissue samples (p < 0.05). In the light on these findings, it can be said that vaginal delivery may decrease the oxidant-induced side effects of oxybutynin as compared to oral delivery.

What Is the Role of Additional Pharmacotherapy and Neuromodulation in Patients with Marginal Benefit from Botulinum Toxin Injection?

PURPOSE OF REVIEW

Third-line therapies for patients with overactive bladder (OAB) can improve symptoms for those who have failed conservative therapies. Options include percutaneous tibial nerve stimulation (PTNS), cystoscopic injection of onabotulinumtoxinA (BTX-A), and sacral neuromodulation (SNM). This paper aims to review the current literature on the treatment of patients with idiopathic OAB who have undergone BTX-A injections and have not responded or have undesirable side effects from the therapy.

RECENT FINDINGS

There are no randomized control trials examining the role of concurrent medical therapy and BTX-A; rather, there are observational studies in the neurogenic population. Furthermore, there are two observational studies on the role of SNM in BTX-A refractory idiopathic OAB patients demonstrating its safety and efficacy. There are many options available to the patient who fails BTX-A. Further research in this specific patient population is necessary to determine why patients have suboptimal responses and to delineate the next step in treatment.

Radiographic Position of the Electrode as a Predictor of the Outcome of InterStim Therapy

Purpose

Sacral neuromodulation (SNM) therapy is indicated for some refractory urological conditions. The electrode lead position in sacral x-rays during routine follow-up may predict the outcome of SNM therapy. To determine whether the radiographic position of the electrode in the sacral foramen predicted the long-term outcome of SNM therapy.

Methods

This was a retrospective study of patients who underwent InterStim SNM at Toronto Western Hospital by 2 surgeons from July 2013 to March 2014. The position of electrodes in relation to the sacral bone was assessed on follow-up sacral x-rays. In the lateral view, we determined the location of the radio-opaque marker of the electrode relative to the inner surface of the sacrum (P3, D3, P2, D2, P1, D1, P0, and D0). In the anteroposterior view, the angle between a line through the spinous process shadow and the electrode was measured (0°–30°, 30°–60°, 60°–90°, >90°, or medial). Dissatisfied patients were defined as those who did not improve based on a voiding diary or those who needed salvage treatment after SNM. The primary endpoint was to determine whether the electrode lead position on sacral x-rays predicted the outcome of SNM therapy.

Results

A total of 69 patients (61 female and 8 male patients) were included, with a median age of 55 years. Forty-two of the patients (60.9%) had refractory overactive bladder, 21 (30.4%) suffered from chronic urinary retention, and 6 (8.7%) had lower urinary tract symptoms and chronic pelvic pain syndrome. The univariate analysis did not show any correlation between SNM response and the electrode position or angle. Dummy regression analysis using response to implantation as the dependent outcome variable did not show any significance for any of the predictors.

Conclusions

Our study did not show a correlation between the long-term response to SNM and the electrode position on follow-up sacral x-rays. In this study, electrode lead position in sacral x-ray at follow-up was not correlated with the outcome of SNM therapy.

Prevalence of overactive bladder in China, Taiwan and South Korea: Results from a cross-sectional, population-based study

Objective

The aim of the present study was to determine the prevalence of overactive bladder (OAB) in individuals aged ≥40 years in China, Taiwan, and South Korea.

Methods

The present cross‐sectional population‐representative Internet‐based study investigated OAB symptoms in men and women aged ≥40 years using the overactive bladder symptom score. Additional instruments included the International Index of Erectile Function (men only) and the Sexual Quality of Life – Female (women only) questionnaires, as well as Patient Perception of Bladder Condition (PPBC).

Results

In all, 8284 individuals participated in the study. The prevalence of OAB was 20.8% overall (women 22.1%, men 19.5%) and increased significantly with age, from 10.8% in those aged 40–44 years to 27.9% in those aged >60 years (P = .001). The presence of comorbid conditions (e.g. neurological disease, diabetes) was associated with a significantly increased prevalence of OAB. Increasing symptom severity was associated with significantly worsening patient perception of bladder condition responses. Just under half (48%) of those with no OAB had no lower urinary tract symptoms (LUTS), whereas 88% of those with severe symptoms had all 3 LUTS (International Continence Society definition) symptom categories (voiding, post‐micturition, and storage symptoms). Of those without OAB, 10% reported visiting healthcare professionals for urinary symptoms, compared with 64% of those with severe OAB symptoms (P = .001). Increased symptom severity was significantly associated with lower sexual quality of life in both men and women.

Conclusions

OAB symptoms were found to affect 1 in 5 individuals aged ≥40 years in China, Taiwan, and South Korea, becoming more common with increasing age. The results suggest that many more individuals with OAB could benefit by consulting healthcare professionals.

Premature contractions of the bladder are suppressed by interactions between TRPV4 and SK3 channels in murine detrusor PDGFRα+ cells

During filling, urinary bladder volume increases dramatically with little change in pressure. This is accomplished by suppressing contractions of the detrusor muscle that lines the bladder wall. Mechanisms responsible for regulating detrusor contraction during filling are poorly understood. Here we describe a novel pathway to stabilize detrusor excitability involving platelet-derived growth factor receptor-α positive (PDGFRα⁺) interstitial cells. PDGFRα⁺ cells express small conductance Ca²⁺-activated K⁺ (SK) and TRPV4 channels. We found that Ca²⁺ entry through mechanosensitive TRPV4 channels during bladder filling stabilizes detrusor excitability. GSK1016790A (GSK), a TRPV4 channel agonist, activated a non-selective cation conductance that coupled to activation of SK channels. GSK induced hyperpolarization of PDGFRα⁺ cells and decreased detrusor contractions. Contractions were also inhibited by activation of SK channels. Blockers of TRPV4 or SK channels inhibited currents activated by GSK and increased detrusor contractions. TRPV4 and SK channel blockers also increased contractions of intact bladders during filling. Similar enhancement of contractions occurred in bladders of Trpv4 ^-/- mice during filling. An SK channel activator (SKA-31) decreased contractions during filling, and rescued the overactivity of Trpv4 ^-/- bladders. Our findings demonstrate how Ca²⁺ influx through TRPV4 channels can activate SK channels in PDGFRα⁺ cells and prevent bladder overactivity during filling.

Stimulation of the pelvic nerve increases bladder capacity in the prostaglandin E2 rat model of overactive bladder

Overactive bladder (OAB) syndrome is a highly prevalent condition that may lead to medical complications and decreased quality of life. Emerging therapies focusing on selective electrical stimulation of peripheral nerves associated with lower urinary tract function may provide improved efficacy and reduced side effects compared with sacral neuromodulation for the treatment of OAB symptoms. Prior studies investigating the effects of pelvic nerve (PelN) stimulation on lower urinary tract function were focused on promoting bladder contractions, and it is unclear whether selective stimulation of the PelN would be beneficial for the treatment of OAB. Therefore our motivation was to test the hypothesis that PelN stimulation would increase bladder capacity in the prostaglandin E₂ (PGE₂) rat model of OAB. Cystometry experiments were conducted in 17 urethane-anesthetized female Sprague-Dawley rats. The effects of intravesical PGE₂ vs. vehicle and PelN stimulation after intravesical PGE₂ on cystometric parameters were quantified. Intravesical infusion of PGE₂ resulted in decreased bladder capacity and increased voiding efficiency without a change in bladder contraction area under the curve, maximum contraction pressure, or contraction duration. Bladder capacity was also significantly decreased compared with vehicle (1% ethanol in saline) confirming that the change in bladder capacity was mediated by PGE₂ PelN stimulation reversed the PGE₂-induced change in bladder capacity and increased the external urethral sphincter electromyogram activity at a specific stimulation condition (amplitude of 1.0 times threshold at 10 Hz). These results confirm that the urodynamic changes reported in conscious rats are also observed under urethane anesthesia and that PelN stimulation is a novel and promising approach for the treatment of the symptoms of OAB.

Optogenetic Modulation of Urinary Bladder Contraction for Lower Urinary Tract Dysfunction

As current clinical approaches for lower urinary tract (LUT) dysfunction such as pharmacological and electrical stimulation treatments lack target specificity, thus resulting in suboptimal outcomes with various side effects, a better treatment modality with spatial and temporal target-specificity is necessary. In this study, we delivered optogenetic membrane proteins, such as channelrhodopsin-2 (ChR2) and halorhodopsin (NpHR), to bladder smooth muscle cells (SMCs) of mice using either the Cre-loxp transgenic system or a viral transfection method. The results showed that depolarizing ChR2-SMCs with blue light induced bladder contraction, whereas hyperpolarizing NpHR-SMCs with yellow light suppressed PGE₂-induced overactive contraction. We also confirmed that optogenetic contraction of bladder smooth muscles in this study is not neurogenic, but solely myogenic, and that optogenetic light stimulation can modulate the urination in vivo. This study thus demonstrated the utility of optogenetic modulation of smooth muscle as a means to actively control the urinary bladder contraction with spatial and temporal accuracy. These features would increase the efficacy of bladder control in LUT dysfunctions without the side effects of conventional clinical therapies.

Overactive bladder - 18 years - Part II

Traditionally, the treatment of overactive bladder syndrome has been based on the use of oral medications with the purpose of reestablishing the detrusor stability. The recent better understanding of the urothelial physiology fostered conceptual changes, and the oral anticholinergics - pillars of the overactive bladder pharmacotherapy - started to be not only recognized for their properties of inhibiting the detrusor contractile activity, but also their action on the bladder afference, and therefore, on the reduction of the symptoms that constitute the syndrome. Beta-adrenergic agonists, which were recently added to the list of drugs for the treatment of overactive bladder, still wait for a definitive positioning - as either a second-line therapy or an adjuvant to oral anticholinergics. Conservative treatment failure, whether due to unsatisfactory results or the presence of adverse side effects, define it as refractory overactive bladder. In this context, the intravesical injection of botulinum toxin type A emerged as an effective option for the existing gap between the primary measures and more complex procedures such as bladder augmentation. Sacral neuromodulation, described three decades ago, had its indication reinforced in this overactive bladder era. Likewise, the electric stimulation of the tibial nerve is now a minimally invasive alternative to treat those with refractory overactive bladder. The results of the systematic literature review on the oral pharmacological treatment and the treatment of refractory overactive bladder gave rise to this second part of the review article Overactive Bladder - 18 years, prepared during the 1st Latin-American Consultation on Overactive Bladder.

The efficacy and tolerability of mirabegron, a β3 adrenoceptor agonist, in patients with symptoms of overactive bladder

Mirabegron, is the only β-3 adrenoreceptor (AR) agonist available for the treatment of overactive bladder (OAB). To assess the efficacy and tolerability of this novel drug therapy, two phase II and six phase III Astellas-sponsored trials have been conducted with over 10,500 adults with OAB recruited. Of these, seven were randomized, double blind, 12-week placebo controlled studies and the other was for 12 months and not placebo controlled. The evidence described would suggest that mirabegron is as efficacious as most antimuscarinics, including tolterodine extended release (ER) 4 mg, compared with placebo with regard to objective measures such as reduction in number of voids per 24 hours, mean volume per void, mean number of episodes of general urinary incontinence, urgency urinary incontinence and urgency per 24 hours; and subjective measures such as severity of urgency, patient perception of bladder condition and validated continence quality of life questionnaires. Regarding tolerability, these data would suggest that patients taking mirabegron suffer a similar rate of adverse effects as those taking placebo alone, whereas the rate in those taking antimuscarinics is greater. Thus mirabegron presents a safe and effective alternative treatment to antimuscarinics for patients with OAB symptoms. Patients who may particularly benefit from mirabegron include those who are unsuitable for antimuscarinics or who have previously struggled with antimuscarinic side effects.

Postmenopausal overactive bladder

Bladder storage symptoms have a severe impact on many areas as regards the quality of life including health-related, social, psychological and working functions. Pharmacotherapy of lower urinary tract stores (LUTS) has been developed to optimize neural control of the lower urinary tract in pathologic states. The bladder can be overactive or underactive. Overactive bladder (OAB) is highly prevalent and is associated with considerable morbidity, especially in aging population. Therefore, an effective treatment of OAB must result in a meaningful reduction in urinary symptoms. Pharmacotherapy for the OAB must be individualized based on the degree of bother, medication side-effect profile, concomitant comorbidities and current medication regimen. Antimuscarinic agents will continue to represent the current gold standard for the first-line pharmacological management of OAB. Alternatively to antimuscarinic therapy, β3-adrenergic receptor agonists, due to their efficacy and favorable adverse event profile, are a novel and attractive option of pharmacological treatment of overactive bladder symptoms. A combination of selective antimuscarinic and β3-adrenergic receptor agonists, agents with the different mechanism of action, gives a new treatment option for the patient with OAB according to its harms profile. A number of putative novel therapeutic agents is under clinical evaluations that may ultimately provide alternative or combination treatment options for OAB in the nearest future.

Pirt reduces bladder overactivity by inhibiting purinergic receptor P2X3

Pirt is a transmembrane protein predominantly expressed in peripheral neurons. However, the physiological and pathological roles of Pirt in hollow viscus are largely unknown. Here we show that Pirt deficiency in mice causes bladder overactivity. The density of α,β-meATP-induced currents is significantly reinforced in Pirt-deficient dorsal root ganglion (DRG) neurons. Pirt and P2X3 receptor co-localize in bladder nerve fibres and heterologous Pirt expression significantly reduces P2X3-mediated currents. Pirt interacts with P2X3 through the N-terminal 14 amino-acid residues. TAT-conjugated Pirt(N14) peptide (Pirt(N14)) is sufficient to inhibit P2X3 activation in bladder DRG neurons and to alleviate bladder overactivity in Pirt(-/-) mice. Pirt expression is decreased in the bladder of cyclophosphamide (CYP)-treated mice, a commonly used model of bladder overactivity. Importantly, Pirt(N14) administration reduces the frequency of bladder voiding and restores the voided volume of CYP-treated mice. Therefore, our results demonstrate that Pirt is an endogenous regulator of P2X3 in bladder function.

Intravesical Sodium Chondroitin Sulphate to Treat Overactive Bladder: Preliminary Result

Purpose:

This study aimed to verify the efficacy and safety of intravesical treatment with sodium chondroitin sulfate (CS) in patients with overactive bladder (OAB) who are refractory to previous antimuscarinic treatment.

Methods:

This study was performed between June 2012 and January 2015 and included 31 consecutive women (mean age, 42.10±7.34 years) with OAB who had been previously treated with two types of antimuscarinic drugs. The results of gynecologic and cystoscopic examinations were normal, and OAB comorbidity was absent. Treatment with intravesical instillations containing 40 mL CS (0.2%; 2 mg/mL) was administered for 6 weeks; after weekly treatments, monthly treatments were administered. The OAB-validated 8 (OAB-V8) symptom scores, nocturia, frequency, urgency, urge incontinence, and urinary volumes measured by uroflowmetry were evaluated for all the patients. The values obtained before the treatment were statistically compared with those obtained six months after the treatment.

Results:

The duration of the symptoms was 18.36±6.19 months. A statistically significant improvement of the patients’ conditions was observed in terms of the OAB-V8 symptom scores, nocturia, frequency, urgency, urge incontinence, and urinary volumes measured by uroflowmetry after the treatment.

Conclusions:

Despite the limitations of this study, the outcomes confirmed that CS therapy is safe and effective for the treatment of OAB.

Central role of the BK channel in urinary bladder smooth muscle physiology and pathophysiology

The physiological functions of the urinary bladder are to store and periodically expel urine. These tasks are facilitated by the contraction and relaxation of the urinary bladder smooth muscle (UBSM), also known as detrusor smooth muscle, which comprises the bladder wall. The large-conductance voltage- and Ca(2+)-activated K(+) (BK, BKCa, MaxiK, Slo1, or KCa1.1) channel is highly expressed in UBSM and is arguably the most important physiologically relevant K(+) channel that regulates UBSM function. Its significance arises from the fact that the BK channel is the only K(+) channel that is activated by increases in both voltage and intracellular Ca(2+). The BK channels control UBSM excitability and contractility by maintaining the resting membrane potential and shaping the repolarization phase of the spontaneous action potentials that determine UBSM spontaneous rhythmic contractility. In UBSM, these channels have complex regulatory mechanisms involving integrated intracellular Ca(2+) signals, protein kinases, phosphodiesterases, and close functional interactions with muscarinic and β-adrenergic receptors. BK channel dysfunction is implicated in some forms of bladder pathologies, such as detrusor overactivity, and related overactive bladder. This review article summarizes the current state of knowledge of the functional role of UBSM BK channels under normal and pathophysiological conditions and provides new insight toward the BK channels as targets for pharmacological or genetic control of UBSM function. Modulation of UBSM BK channels can occur by directly or indirectly targeting their regulatory mechanisms, which has the potential to provide novel therapeutic approaches for bladder dysfunction, such as overactive bladder and detrusor underactivity.