Randomized double-blind, active-controlled phase 3 study to assess 12-month safety and efficacy of mirabegron, a β(3)-adrenoceptor agonist, in overactive bladder. Eur Urol. 2013;63:296-305. [PMID: 23195283 DOI: 10.1016/j.eururo.2012.10.048]

Comparison of the effects of β3 -adrenoceptor agonism on urinary bladder function in conscious, anesthetized, and spinal cord injured rats

AIMS

To compare the dose effect relationship of a selective β3 -adrenoceptor agonist (CL-316,243) on cystometric parameters in anesthetized and conscious rats and to evaluate its effect in a model of neurogenic bladder overactivity induced by spinal cord injury (SCI).

METHODS

Experiments were performed in anesthetized and conscious normal rats and in conscious rats after complete transection at the T8 level of the spinal cord. The jugular vein and urinary bladder were catheterized and the bladder infused with saline. CL-316,243 was tested intravenously at 0.01, 0.03, and 0.1 mg/kg in anesthetized and conscious rats and at 0.01 mg/kg in sham and SCI rats. Intravesical pressure was recorded for 1 hr following drug administration. Intercontraction interval (ICI), amplitude of micturition (AM), micturition frequency (MF) and non-voiding contractions (NVC) were analyzed.

RESULTS

In anesthetized and conscious normal rats, CL-316,243 significantly increased ICI in a dose-dependent manner. In anesthetized rats, AM was significantly decreased at all doses tested whereas in conscious rats, a significant decrease (-19 ± 6%) in AM was only observed at the highest dose (0.1 mg/kg). In conscious sham and SCI rats, CL-316,243 significantly increased ICI (42 ± 17% and 49 ± 17%, respectively) and decreased MF without affecting AM. In SCI rats, CL-316,243 reduced the frequency of NVC (-53 ± 14%) without significant effects on amplitude.

CONCLUSIONS

The current results suggest that anesthesia can alter the effects of β3 -adrenoceptor agonists in experimental models. In addition, this is the first demonstration that stimulation of β3 -adrenoceptors can produce decreases in micturition frequency and NVC in SCI rats without affecting AM.

Mirabegron for male lower urinary tract symptoms

Benign prostatic hyperplasia (BPH) is a common cause of lower urinary tract symptoms (LUTS) in men. Patients with BPH often present with a combination of obstructive and overactive bladder (OAB) symptoms. It is postulated that bladder outlet obstruction (BOO) from BPH results in concomitant OAB symptoms through ischemic induced variations in the response to neurotransmitters of both the detrusor and the urothelium. This altered response leads to the pathologic activation of the micturition reflex, generating sensory dysfunction and involuntary bladder contractions. Alpha-1 adrenoceptor antagonists (alpha-blockers) and 5-alpha reductase inhibitors (5-ARIs) are commonly used to treat the BOO caused by BPH. Anticholinergic agents are frequently used to treat concurrently OAB symptoms caused by the BOO. Unfortunately, anticholinergic medications demonstrate bothersome side effects and a theoretical risk of urinary retention. Basic science and clinical research has led to the development of a new class of pharmaceuticals for the treatment of overactive bladder with diminished risk of urinary retention and lacking many anticholinergic side effects. This novel compound, mirabegron (Mybertriq, Astellas Pharma US, Inc.), is a β₃-adrenoceptor agonist and represents a promising new class of oral agents designed for the treatment of OAB symptoms, with minimal effect on voiding.

Contemporary issues with pharmacotherapy for lower urinary tract symptoms

Two articles appeared in the November 2012 edition of the journal evaluating aspects relating to the use of two important pharmacotherapeutic classes for lower urinary tract symptoms (LUTS) in real life clinical practice. LUTS is a non-specific term that encompasses urine storage, voiding and postmicturition symptoms. LUTS is a common bothersome problem affecting both men and women with a comparable prevalence in age-matched patients of both sexes that increases with ageing.

Effects of duloxetine and WAY100635 on pudendal inhibition of bladder overactivity in cats

This study was aimed at determining the effect of duloxetine (a serotonin-norepinephrine reuptake inhibitor) on pudendal inhibition of bladder overactivity. Cystometrograms were performed on 15 cats under α-chloralose anesthesia by infusing saline and then 0.25% acetic acid (AA) to induce bladder overactivity. To inhibit bladder overactivity, pudendal nerve stimulation (PNS) at 5 Hz was applied to the right pudendal nerve at two and four times the threshold (T) intensity for inducing anal twitch. Duloxetine (0.03-3 mg/kg) was administered intravenously to determine the effect on PNS inhibition. AA irritation significantly (P < 0.01) reduced bladder capacity to 27.9 ± 4.6% of saline control capacity. PNS alone at both 2T and 4T significantly (P < 0.01) inhibited bladder overactivity and increased bladder capacity to 83.6 ± 7.6% and 87.5 ± 7.7% of saline control, respectively. Duloxetine at low doses (0.03-0.3 mg/kg) caused a significant reduction in PNS inhibition without changing bladder capacity. However, at high doses (1-3 mg/kg) duloxetine significantly increased bladder capacity but still failed to enhance PNS inhibition. WAY100635 (N-[2-[4-(2-methoxyphenyl)-1-piperazinyl]ethyl]-N-(2-pyridyl)cyclohexanecarboxamide; a 5-HT1A receptor antagonist, 0.5-1 mg/kg i.v.) reversed the suppressive effect of duloxetine on PNS inhibition and significantly (P < 0.05) increased the inhibitory effect of duloxetine on bladder overactivity but did not enhance the effect of PNS. These results indicate that activation of 5-HT1A autoreceptors on the serotonergic neurons in the raphe nucleus may suppress duloxetine and PNS inhibition, suggesting that the coadministration of a 5-HT1A antagonist drug might be useful in enhancing the efficacy of duloxetine alone and/or the additive effect of PNS-duloxetine combination for the treatment of overactive bladder symptoms.

Neurogenic overactive bladder in spinal cord injury and multiple sclerosis: role of onabotulinumtoxinA

People with neurogenic overactive bladder from either multiple sclerosis or spinal cord injury often suffer significant morbidity and decreased quality of life. Here we review the pathophysiology of neurogenic overactive bladder and the impact it can have on people with multiple sclerosis or spinal cord injury. We also address the various traditional treatment options and focus on the use of botulinum toxin A (specifically onabotulinumtoxinA) for this condition.

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

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

Discovery history and clinical development of mirabegron for the treatment of overactive bladder and urinary incontinence

INTRODUCTION

Overactive bladder (OAB) and urinary incontinence, although not life-threatening, are very bothersome chronic health conditions. The limitations of current pharmacological treatment urge the need for novel drugs with alternative mechanisms of action. Huge efforts in this area of research led to the synthesis of several selective and potent β3-adrenoceptor agonists that gained relevance through research during the late 80s and 90s. Mirabegron was the first compound of this new class of drugs that showed preclinical efficacy in several models of storage bladder dysfunction, together with a favorable human pharmacological profile. Having passed the proof-of-concept stage, an extensive clinical development and pharmacology program was performed during the last 10 years, involving >10,000 individuals, before mirabegron was granted marketing approval.

AREAS COVERED

In this case history, the authors review the milestones in mirabegron's discovery based on a systematic literature review.

EXPERT OPINION

Thanks to its tolerability and safety/efficacy balance, mirabegron has potential to fill a need for new treatment options for OAB, and paves the way for further development of a completely new class of drugs aimed to treat this condition. However, the exact role of mirabegron in clinical practice has yet to be defined. Further studies are needed in order to clarify, together with post-launch information, critical safety issues and cost-effectiveness in head-to-head comparison with current standard treatments.

New agents to treat lower urinary tract and pelvic floor disorders

For patients with overactive bladder and a suboptimal response to antimuscarinic therapy, there are several options to consider including alteration of the antimuscarinic regimen, switching to an agent with an alternate mechanism of action (i.e., mirabegron), posterior tibial nerve stimulation, or botulinum toxin. These options are summarized in this brief review.

Pilot study of liposome-encapsulated onabotulinumtoxina for patients with overactive bladder: a single-center study

BACKGROUND

Intradetrusor onabotulinumtoxinA (BoNT-A) injection benefits overactive bladder (OAB) patients, but increased postvoid residual (PVR) urine volume and urinary tract infection (UTI) remain risks. Intravesical instillation of liposomal BoNT-A instead of injection could prevent such adverse events.

OBJECTIVE

To evaluate instillation of liquid liposomal BoNT-A (Lipotoxin) for the treatment of OAB and to determine its mechanism of action.

DESIGN, SETTING, AND PARTICIPANTS

A double-blind randomized parallel controlled pilot trial in 24 OAB patients at a single tertiary center.

INTERVENTION

Patients were randomly assigned to intravesical instillation of Lipotoxin containing 80 mg liposomes and 200 U BoNT-A or normal saline (N/S). Patients were retreated with Lipotoxin 1 mo later if they failed the first treatment.

OUTCOME MEASUREMENT AND STATISTICAL ANALYSIS

Voiding diaries, OAB symptom scores, urodynamic studies, and adverse events were monitored. The primary end point was change of total urinary frequency per 3 d at 1 mo after treatment. Immunohistochemistry and Western blotting for synaptic vesicle glycoprotein 2A (SV2A) and synaptosomal-associated protein, 25 kDa (SNAP25) were performed at baseline and 3 mo after treatment. The Wilcoxon rank sum test and Wilcoxon signed rank test were used for statistical analysis.

RESULTS AND LIMITATIONS

At 1 mo after treatment, the change of urinary frequency per 3 d significantly improved in the Lipotoxin group (n=12; median: -6.50; interquartile range [IQR]: -18.3 to -0.25; p=0.008) but not in the N/S group. (n=12.0; IQR: -7.75 to 8.0; p=0.792). Urgency episodes also showed a significant decrease in the Lipotoxin group (-12.0; IQR: -20.3 to -2.75; p=0.012) but not in the N/S group (-1.0; IQR: -11.0 to 2.5; p=0.196). SV2A and SNAP25 were expressed in urothelial cells and suburothelial tissues. However, the protein expression did not significantly differ between responders and nonresponders at 3 mo after treatment.

CONCLUSIONS

Intravesical Lipotoxin instillation effectively reduced frequency episodes 1 mo after treatment in OAB patients without any increase in PVR or risk of UTI.

PATIENT SUMMARY

We demonstrated that intravesical Lipotoxin instillation reduced frequency episodes at 1 mo in overactive bladder patients. This procedure is safe, without an increase in postvoid residual or the risk of urinary tract infection.

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

Introduction

Overactive bladder (OAB) is a prevalent condition that has a significant impact on quality of life. The usual treatment approach is both behavioral and pharmacological. The first-line pharmacological treatment commonly utilizes anticholinergic agents, which may be limited by their tolerability, efficacy, and long-term compliance. Developments in elucidating the pathophysiology of OAB and alternative targets for pharmacological therapy have led to newer agents being developed to manage this condition. These agents include mirabegron and botulinum toxin, which have alternate mechanism of action and avoid the anticholinergic side effects.

Objectives

To provide an update for clinicians managing OAB with an overview of the existing and newer medical options for OAB, including pharmacology, efficacy, side-effect profile, tolerability, and impact on patient quality of life.

Methods

PubMed and Medline were searched for randomized controlled drug trials in adults with OAB, meta-analyses of medical therapy for OAB, and individual drug names, including the keywords efficacy, tolerability, quality of life, and compliance. Nonhuman studies, pediatric trials, and those involving patients with neurogenic bladder dysfunction (with the exception of studies involving botulinum toxin A) were excluded.

Results

There is level 1, Grade A evidence to support the efficacy of anticholinergic drugs, botulinum toxin, and mirabegron for OAB. Long-term compliance with anticholinergic medications is limited. The mechanism of action, effectiveness, and side effects of these drugs are discussed, and where the data are available compared with other OAB medications.

Conclusion

Most of the anticholinergic agents have comparative efficacies and core side-effect profiles, with individual variations relating to their muscarinic receptor selectivity, pharmacokinetics, and metabolism. Newer agents, with alternative sites of action, such as mirabegron and botulinum toxin, provide additional treatment options for patients intolerant to or inadequately treated with anticholinergics.

Do β-adrenoceptor agonists induce homologous or heterologous desensitization in rat urinary bladder?

β3-Adrenoceptor agonists have recently been introduced for the symptomatic treatment of the overactive bladder syndrome. As such treatment is not curative, long-term treatment is anticipated to be required. As the susceptibility of β3-adrenoceptors to undergo agonist-induced desensitization is cell type- and tissue-dependent, we have explored whether pre-treatment with a β-adrenoceptor agonist will attenuate subsequent relaxation responses to freshly added agonist using rat urinary bladder as a model. We have used the prototypical β-adrenoceptor agonist isoprenaline, the β2-selective fenoterol and the β3-selective CL 316,243 and mirabegron as well as the receptor-independent bladder relaxant forskolin. We show that a 6-h pre-treatment with agonist can significantly reduce subsequent relaxation against KCl-induced smooth muscle tone, but agonist-induced desensitization was also observed with longer pre-treatments or against passive tension. The agonist-induced desensitization was prominent for the β2 component of rat bladder relaxation but much weaker or even absent for the β3 component. Moreover, β-adrenoceptor agonist pre-treatment reduced contractile responses to the muscarinic agonist carbachol and the receptor-independent stimulus KCl. Taken together these data do not support the hypothesis that the long-term clinical efficacy of β3-adrenoceptor agonists in the treatment of the overactive bladder syndrome will be limited by receptor desensitization. Rather they raise the possibility that such treatment may not only cause smooth muscle relaxation but also may attenuate hyper-contractility of the bladder.

Mirabegron, a novel, non-antimuscarinic drug for the overactive bladder: An up-to-dated review

Mirabegron opened a new era in the treatment of overactive bladder (OAB). For the first time physicians dealing with OAB have an effective alternative to the pharmacological mainstay of the therapy for this disorder, the antimuscarinic drugs. This first-in-class, potent β3-adrenoceptors agonist has recently received approval by regulatory authorities in Japan, United States and Europe, based on the favourable efficacy-tolerability profile demonstrated in multiple randomized, multinational, controlled trials, both short and long-term. There is substantial consistency through the studies in reporting the cardiovascular safety of treatment with mirabegron. The main advantage of mirabegron is the placebo-like incidence of classic adverse effects caused by antimuscarinics, dry mouth and constipation, that is expected to improve long-term adherence of patients to treatment. Mirabegron can be used in patients with contraindications to antimuscarinics and in those who discontinued previous antimuscarinic therapy. Herein, we reviewed the published literature on mirabegron, focusing on the rationale of β3-agonism for OAB treatment and on the preclinical and clinical evidence of efficacy and safety available on this new pharmacological principle.

Evidence available on the use of the selective β3-adrenoceptor agonist mirabegron for the treatment of overactive bladder

CONTEXT

Mirabegron, the selective β3-adrenoceptor agonist, heralds the latest development for the treatment of overactive bladder (OAB).

OBJECTIVE

To present the evidence available on the efficacy and tolerability of mirabegron and to discuss this treatment's potential in our setting.

EVIDENCE ACQUISITION

We reviewed 11 studies conducted with mirabegron in patients with OAB (2 phase II, 9 phase III), all studies were compared to placebo with 6 studies also including tolterodine as an additional arm. Greater emphasis shall be given to the main phase III trials performed in Europe, the USA and Australia evaluating efficacy and safety after 12 weeks (NCT00662909, NCT00689104, NCT00912964) and safety after 12 months (NCT00688688). The combined analyses of these 12 week studies is also available, with emphasis on global efficacy (FAS), efficacy with regard to incontinence (FAS i) and safety (SAF). More than 50% of patients had previously discontinued anticholinergics medication for OAB, thus allowing us to obtain data on the effectiveness of mirabegron in patients already treated with anticholinergics.

EVIDENCE SYNTHESIS

Mirabegron is an efficacious drug which presents a statistically significant reduction in the number of incontinence episodes and in urinary frequency as of 4 weeks, with a higher percentage of dry patients and a higher percentage of patients with reduction ≥50% in the number of incontinence episodes than placebo. The efficacy of mirabegron 50 and 100mg in the reduction of incontinence episodes occurs in de novo patients and who have received antimuscarinics, with adjusted mean difference and improvement in urinary frequency greater in treated patients. Its tolerability is very similar to placebo particularly for the adverse effects of the antimuscarinics (dry mouth, constipation and blurred vision). A minimal, non-clinically significant change is observed in systolic and diastolic blood pressure and pulse. Its efficacy is long-term. Mirabegron at the doses of 50 and 100mg presents an improvement versus placebo in patient satisfaction, health-related quality of life (HRQoL), symptom bother and patient's perception of bladder condition (PPBC). In the 12 week Phase III European study tolterodine delivered a lesser degree of improvement than mirabegron versus placebo in patient satisfaction, HRQoL, symptom bother and PPBC.

CONCLUSIONS

Mirabegron is the first of a new class of compounds with a novel mechanism of action that is different to the antimuscarinics. It presents significant and clinically important efficacy in the treatment of the symptoms of OAB. It has advantages with regard to the results described by the patient in treatment satisfaction. Studies on its combined use with anticholinergics are ongoing.

Impact of mirabegron extended-release on the treatment of overactive bladder with urge urinary incontinence, urgency, and frequency

Overactive bladder is a highly prevalent disorder with a significant impact on quality of life. Antimuscarinic agents are commonly used, but persistence is limited due to unsatisfactory efficacy and/or tolerability. Mirabegron is the first beta-3 adrenoceptor agonist approved for the treatment of overactive bladder syndrome. This paper reviews the pharmacology, mechanism of action, efficacy, and safety of mirabegron. A PubMed search of all English articles pertaining to mirabegron was performed. An alternative to antimuscarinics, mirabegron has a unique mechanism, improves overactive bladder symptoms and quality of life, and has limited adverse effects and few contraindications.

Mirabegron in overactive bladder: a review of efficacy, safety, and tolerability

AIMS

Mirabegron, the first β3 -adrenoceptor agonist to enter clinical practice, has a different mechanism of action from antimuscarinic agents. This review presents data on the efficacy, safety, and tolerability of mirabegron in studies conducted to date.

METHODS

All clinical data on mirabegron that are currently in the public domain are included, including some in-press manuscripts.

RESULTS

In Phase III clinical trials in patients with overactive bladder (OAB), mirabegron at daily doses of 25, 50, and 100 mg demonstrated significant efficacy in treating the symptoms of OAB, including micturition frequency, urgency incontinence, and urgency. Significant improvements in micturition frequency, urgency incontinence, and mean volume voided/micturition were seen as early as the first assessment (week 4) for mirabegron 50 and 100 mg, and were maintained throughout treatment. Responder analyses showed a significant improvement with mirabegron 50 and 100 mg in terms of dry rates, ≥50% reduction in mean number of incontinence episodes/24 hr, and the proportion of patients with ≤8 micturitions/24 hr at final visit. The benefit of mirabegron 50 and 100 mg was also evident in patients ≥65 years of age, and in both treatment-naïve patients and those who previously discontinued antimuscarinic therapy. These data therefore demonstrate a clinically meaningful benefit with mirabegron in the objective endpoints of OAB. Assessment of measures of health-related quality of life and treatment satisfaction showed that patients perceived treatment with mirabegron as meaningful. In OAB clinical trials of up to 12 months mirabegron appeared to be well tolerated. The most common adverse events (AEs) observed with mirabegron in clinical trials of up to 12 months were hypertension, nasopharyngitis, and urinary tract infection. The incidence of dry mouth was similar to placebo, and was between three and fivefold less than for tolterodine extended release 4 mg. Since dry mouth is the most bothersome AE associated with antimuscarinic drugs and often a reason for treatment discontinuation, mirabegron may be a valuable treatment option for these patients.

CONCLUSIONS

In Phase III clinical trials, mirabegron at daily doses of 25, 50, and 100 mg demonstrated significant efficacy in treating symptoms of OAB and, at doses of 50 and 100 mg, demonstrated significant improvements versus placebo on key secondary endpoints, as early as the first assessment (week 4), and these were maintained throughout treatment. In OAB clinical trials of up to 12 months, mirabegron appeared to be well tolerated.

Overactive bladder syndrome: Current pathophysiological concepts and therapeutic approaches

Objectives

The overactive bladder syndrome (OAB) is a highly prevalent and bothersome symptom complex. We review contemporary reports to provide an update of the key aspects of its pathogenesis and the therapeutic approaches.

Methods

The PUBMED database was searched for relevant publications in the period from 1 January 1985 to 1 May 2013, using the keywords ‘overactive bladder’, ‘anti-muscarinics’, ‘β-3 agonists’, ‘intravesical botulinum toxin’, ‘tibial nerve stimulation and ‘sacral neuromodulation’.

Results

In all, 33 articles were selected for this review. OAB is very common, affecting 10–20% of the population. It is often bothersome and frequently affects the quality of life. The current definition of OAB remains a source of controversy. Anti-muscarinic agents remain the mainstay of pharmacotherapy. The new β-3 agonists have some efficacy whilst avoiding anti-cholinergic effects, and so might benefit patients who are unable to tolerate anti-muscarinic agents. Intravesical botulinum toxin is recommended for patients in whom oral pharmacotherapy fails, although the optimal parameters in terms of dosing, number of injections and injection site are yet to be fully established. Sacral neuromodulation is another option that has a good response in about half of patients.

Conclusions

OAB remains an incompletely understood problem that presents a significant management challenge. A range of therapeutic options is now available for clinicians managing this problem.

Urodynamic studies in spinal cord tethering

INTRODUCTION

Tethered cord syndrome (TCS) is of particular interest to urologists through its effects on the function of the lower urinary tract. Tethering of the spinal cord can result in bladder dysfunction with multiple manifestations, clinically raging from urinary retention and detrusor under-activity to urinary incontinence, over-activity of the detrusor, and sphincter dysfunction. Goals of management include protecting renal function and preserving patient quality of life.

METHODS

Evaluation of a TCS patient with urinary complaints begins with a thorough history and physical examination. Further characterization of urinary symptoms with a voiding diary provides vital information that helps to direct treatment while engaging the patient and family in the treatment plan. Urodynamic studies then provide key diagnostic data regarding bladder function, bladder outlet resistance, and urinary sphincter function. In the pediatric population, particular care must be paid to counseling patients and their families prior to the procedure to alleviate the often-considerable anxiety associated with an invasive procedure.

CONCLUSION

The armamentarium for management of neurogenic bladder associated with TCS includes behavioral training, biofeedback therapy, medications, patient-performed procedures, and surgical intervention. The choice of intervention depends on the patient's symptoms, urodynamic findings, and patient and family preferences. The primary problem of TCS should be addressed first through detethering, and then the urological team can use progressively more aggressive therapies as necessary. Interpretation and treatment by a dedicated, specialized, multidisciplinary team that includes the pediatric urologist, pediatric neurosurgeon and dedicated nurse practitioner, is critical for successful treatment.

Mirabegron for overactive bladder syndrome

Urinary incontinence, the involuntary leakage of urine, can result from abnormalities of the urinary tract or may be caused by other conditions and is sub-divided into a number of classifications including stress incontinence and urge urinary incontinence.(1) Urge urinary incontinence (UUI) is involuntary urine leakage accompanied by urgency of micturition.(2) Overactive bladder (OAB) syndrome is defined as urgency occurring with or without UUI and usually occurs with frequency and nocturia.(1) Wet OAB is associated with UUI, while dry OAB is not associated with incontinence. Current drug therapy for OAB involves the use of an antimuscarinic drug, of which there are a number available, such as oxybutynin, darifenacin, solifenacin and tolterodine.(1,3) ▾Mirabegron is the first of a new class of drug, beta-3-adrenoreceptor agonists, licensed for symptomatic treatment of urgency, increased micturition frequency and/or urgency incontinence as may occur in adult patients with OAB syndrome.(4) Here we review the evidence for mirabegron.

New developments in the medical management of overactive bladder

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

The efficacy and safety of mirabegron in treating OAB: a systematic review and meta-analysis of phase III trials

PURPOSE

Mirabegron, a potent and selective β3-adrenoceptor agonist, has been developed for the treatment of overactive bladder (OAB). We carried out a systematic review and meta-analysis to assess the efficacy and safety of the drug for treating OAB.

METHODS

A literature review was performed to identify all published randomized double-blind, placebo-controlled phase III trials of mirabegron for the treatment of OAB. The search included the following databases: MEDLINE, EMBASE and the Cochrane Controlled Trials Register. The reference lists of the retrieved studies were also investigated. A systematic review and meta-analysis of phase III trials were conducted.

RESULTS

Four publications involving a total of 5,761 patients were used in the analysis, including four phase III RCTs that compared mirabegron with placebo. We found that mirabegron was effective in treating OAB in our meta-analysis. Co-primary efficacy end points: the mean number of incontinence episodes per 24 h (the standardized mean difference (SMD) = -0.44, 95 % confidence interval (CI) -0.59 to -0.29, p < 0.00001); the mean number of micturitions per 24 h (SMD = -0.62, 95 % CI -0.80 to -0.45, p < 0.00001) and key secondary efficacy end points: mean volume voided per micturition; mean number of urgency episodes per 24 h indicated that mirabegron was more effective than the placebo. Safety assessments included common treatment-emergent adverse events (TEAEs) [OR 1.10, 95 % CI 0.93-1.31, p = 0.25), hypertension, cardiac arrhythmia TEAEs, urinary retention and discontinuations due to adverse event indicated that mirabegron was well tolerated.

CONCLUSIONS

This meta-analysis indicates that mirabegron to be an effective and safe treatment for OAB symptoms with a low occurrence of side effects. It offers promise as an effective oral agent for the treatment of OAB with a distinct efficacy/tolerability balance.

Neuromodulation for overactive bladder

Overactive bladder (OAB) affects millions of people worldwide yet first-line treatments are often poorly tolerated and compliance rates are low. Neuromodulation works via afferent nerve modulation and offers a minimally invasive and reversible alternative treatment option for patients with OAB who have failed first-line therapy. Neuromodulation has revolutionized the management of OAB and is now well established as a safe and effective treatment for those refractory to conservative treatments. Multiple neuroanatomical pathways have been described for sacral neuromodulation including the S3 nerve root, pudendal nerve and tibial nerve. The S3 nerve root is currently the main treatment target and has the most long-term data on safety and efficacy to support its use. However, studies on neuromodulation at the pudendal nerve or posterior tibial nerve have been positive and their role in treatment continues to evolve. Most urologists who are experienced in voiding dysfunction can become proficient in each technique. Patient selection, surgical techniques and postoperative management differ slightly between approaches and urologists should familiarize themselves with these differences. Treatment of OAB should progress from the least to most invasive modality, and neuromodulation provides an attractive option owing to its minimally invasive approach, tolerability, positive outcomes and reversibility.

Protective effect of a β3-adrenoceptor agonist on bladder function in a rat model of chronic bladder ischemia

BACKGROUND

The β3-adrenoceptor (AR) agonist mirabegron has been introduced as a treatment for the overactive bladder. Its effects on the function of the ischemic bladder are not known.

OBJECTIVE

To investigate the effect of mirabegron in a rat model of chronic ischemia-related bladder dysfunction.

DESIGN, SETTING, AND PARTICIPANTS

Male Sprague-Dawley rats were divided into three groups: control (n=10), arterial endothelial injury (AI; n=16), and AI with mirabegron treatment (AI-mirabegron; n=10). AI and AI-mirabegron groups underwent endothelial injury of the iliac arteries and received a 2% cholesterol diet following AI. AI-mirabegron rats received mirabegron (10mg/kg/d) orally for 8 wk. The control group received a regular diet.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

After 8 wk, urodynamic investigation was performed in awake animals. Pharmacologic in vitro studies and histologic examination of the iliac arteries and bladders were performed.

RESULTS AND LIMITATIONS

Iliac arteries from both AI and AI-mirabegron rats displayed neointimal formation and luminal occlusion. Micturition interval (MI), bladder capacity (Bcap), and voided volume (VV) in the AI group were significantly less than in the control group (p<0.01). In the AI-mirabegron group, MI, Bcap, and VV were significantly larger than in the AI group (p<0.05) but significantly less than in the control group (p<0.05). Contractile responses of bladder strips to potassium chloride, electrical field stimulation, and carbachol were significantly lower after AI than in controls; responses in preparations from AI-mirabegron-treated animals were similar to those of controls. The AI group showed a significantly higher percentage of collagen (28.6 ± 1.57%) compared with the controls (8.65 ± 0.67%) and AI-mirabegron-treated animals (17.2 ± 2.32%). The mirabegron dose used in this study may potentially limit the translational value of the results.

CONCLUSIONS

In the chronically ischemic rat bladder, treatment with mirabegron seems to protect bladder function and morphology, resulting in reduced bladder hyperactivity. If the results are valid for humans, they support β3-AR agonism as a potential treatment of chronic ischemia-related bladder dysfunction.

Mirabegron: β3-Adrenergic Receptor Agonist for the Treatment of Overactive Bladder

OBJECTIVE

To review the place in therapy of mirabegron, a new oral β3-adrenergic receptor agonist, for the treatment of overactive bladder (OAB).

DATA SOURCES

A literature search of MEDLINE and MEDLINE In-Process & Other Non-Indexed Citations Databases (1996-April 2013) was conducted using the key words mirabegron, receptor, adrenergic, beta-3; adrenergic beta-3 receptor; beta-3 receptor, and overactive bladder; urinary bladder; overactive. All published articles regarding mirabegron were included. References of selected articles, data from poster presentations, and abstract publications were additionally reviewed.

STUDY SELECTION AND DATA EXTRACTION

Available English-language data from reviews, abstracts, presentations, and clinical trials of mirabegron in humans were reviewed; relevant clinical data were selected and included.

DATA SYNTHESIS

Mirabegron is the newest option for treatment of OAB with symptoms of urge incontinence. As a β3-receptor agonist, it reduces bladder muscle contractions. In two 12-week, randomized, double-blind, placebo-controlled Phase 3 studies, mirabegron significantly reduced the number of incontinence episodes per 24 hours from baseline (−1.47, −1.63, and −1.13; p < 0.05; and −1.57, −1.46, and −1.17; p < 0.05; all values for mirabegron 50 mg, 100 mg, and placebo). Micturitions per 24 hours were also reduced from baseline (−1.66, −1.75, and −1.05; p < 0.05; and −1.93, −1.77, and −1.34; p < 0.05; all values for mirabegron 50 mg, 100 mg, and placebo). A 12-month trial found mirabegron to have a safety and efficacy profile similar to that of tolterodine.

CONCLUSIONS

Treatment of OAB initially includes lifestyle and nonpharmacologic intervention; for patients with persistent symptoms despite these treatments, drug therapy represents a next-step approach for symptom control. Mirabegron alleviates symptoms of OAB while having a mechanism of action that provides an alternative for patients who are intolerant of or who have contraindications to anticholinergic agents. The place in therapy of mirabegron relative to anticholinergics in the treatment of urge incontinence has not yet been established.

New developments in the management of overactive bladder: focus on mirabegron and onabotulinumtoxinA

In the last few years, much new information has been generated on the pathophysiology, possible therapeutic targets, and pharmacologic treatment of overactive bladder (OAB). Antimuscarinic drugs are still first-line pharmacologic treatment for OAB and often have good initial response rates, but adverse effects and decreasing efficacy cause long-term compliance problems, prompting a search for new therapeutic alternatives. Mirabegron and onabotulinumtoxinA, two drugs with different mechanisms of action, and with adverse effect profiles different from those of antimuscarinics, were recently approved for treatment of OAB. However, their place in the treatment of this disorder has not yet been established. In this short review, the mechanisms of action, clinical efficacy, and safety profiles of these drugs are discussed and compared with those of the current gold standard, antimuscarinic agents.