Prospective Pilot Study of Mirabegron in Pediatric Patients with Overactive Bladder

Overactive bladder in children

Overactive bladder (OAB) is a highly prevalent disorder in the pediatric population. This condition is especially troublesome for pediatric patients and their families when associated with incontinence, since it negatively affects self-esteem and impairs children's development. From the patient's perspective, urgency and urge incontinence can have a significant impact, negatively affecting their quality of life. For a therapy to have true benefit, changes must not only be statistically significant, but must also be perceived as meaningful by the patient. A stepwise approach is favoured to treat this pathology, starting with behavioural therapy, followed by medical management, and eventually more invasive procedures. Antimuscarinic agents are the mainstay of medical treatment for OAB. Oxybutynin is the most commonly used antimuscarinic in the pediatric population. However, some patients have a suboptimal response to antimuscarinics and many experience bothersome side effects, which have been documented with all antimuscarinics to a significantly higher degree than placebo. Although there have been reports about the use of tolterodine, fesoterodine, trospium, propiverine, and solifenacin in children, to date, only oxybutynin has been officially approved for pediatric use by medical authorities in North America. This review will address alternative treatment options for pediatric patients presenting with OAB, from conservative measures to more invasive therapies.

Bladder and bowel dysfunction in children: An update on the diagnosis and treatment of a common, but underdiagnosed pediatric problem

Bladder and bowel dysfunction (BBD) describes a spectrum of lower urinary symptoms (LUTS) accompanied by fecal elimination issues that manifest primarily by constipation and/or encopresis. This increasingly common entity is a potential cause of significant physical and psychosocial burden for children and families. BBD is commonly associated with vesicoureteral reflux (VUR) and recurrent urinary tract infections (UTIs), which at its extreme may lead to renal scarring and kidney failure. Additionally, BBD is frequently seen in children diagnosed with behavioural and neuropsychiatric disorders such as attention-deficit/hyperactivity disorder (ADHD) and autism spectrum disorder (ASD). Patients with concomitant BBD and neuropsychiatric disorders have less favourable treatment outcomes. Early diagnosis and treatment of BBD are critical to avoid secondary comorbidities that can adversely impact children's kidney and bladder function, and psychosocial well-being. The majority of patients will improve with urotherapy, adequate fluid intake, and constipation treatment. Pharmacological treatment must only be considered if no improvement occurs after intensive adherence to at least six months of urotherapy ± biofeedback and constipation treatment. Anticholinergics remain the mainstay of medical treatment. Selective alpha-blockers appear to be effective for improving bladder emptying in children with non-neurogenic detrusor overactivity (DO), incontinence, recurrent UTIs, and increased post-void residual (PVR) urine volumes. Alpha-1 blockers can also be used in combination with anticholinergics when overactive bladder (OAB) coexists with functional bladder outlet obstruction. Minimally invasive treatment with onabotulinumtoxinA bladder injections, and recently neurostimulation, are promising alternatives for the management of BBD refractory to behavioural and pharmacological treatment. In this review, we discuss clinical presentation, diagnostic approach, and indications for behavioural, pharmacological, and surgical treatment of BBD in children based on a thorough literature review. Expert opinion will be used when scientific evidence is unavailable.

Dual Therapy for Refractory Overactive Bladder in Children: A Prospective Open-Label Study

PURPOSE

Mirabegron (β3 adrenoreceptor agonist) is a new molecule with a mechanism of action distinct from antimuscarinics. Combination therapy with solifenacin was recently studied in an adult population. We evaluated the efficacy and safety of mirabegron as add-on therapy to treat urinary incontinence in children with idiopathic overactive bladder refractory/intolerant to antimuscarinics.

MATERIALS AND METHODS

A prospective off-label study using add-on regimens of mirabegron was conducted in pediatric patients presenting with no symptom improvement while undergoing intensive behavioral and medical therapies and/or significant side effects while undergoing antimuscarinic dose escalation. Our primary outcome was better reported efficacy than with the use of prior antimuscarinic monotherapy. Secondary end points were tolerability, safety and satisfaction. Efficacy and tolerability were assessed based on voiding diaries, post-void residuals, urine cultures, electrocardiograms and vital signs. Families were questioned regarding continence, side effects and compliance. Wilcoxon signed-rank test was used for statistical analysis.

RESULTS

A total of 35 patients were recruited at a median age of 10.3 years and were administered add-on mirabegron for a median of 16.4 months. Median bladder capacity improved from 50% to 74% expected bladder capacity (p <0.001). Continence improved in all patients, with 12 being completely dry. Post-void residual was increased in 2 patients and 1 urinary tract infection was reported. Seven patients reported mild or moderate side effects, with 2 withdrawals because of side effects (1 patient) and post-void residual (1).

CONCLUSIONS

Add-on mirabegron appears to be a safe alternative for children with refractory overactive bladder. Dual therapy is well tolerated and adjusted dose regimen appears safe in this first pediatric study.