OnabotulinumtoxinA as effective as, safer than pharmacotherapy for OAB

Women with refractory overactive bladder (OAB) may improve their symptoms by using either intradetrusor onabotulinumtoxinA or combined pharmacotherapy with solifenacin and mirabegron, suggests a study.

However, “onabotulinumtoxin A offers a more favourable safety profile and is a more appropriate choice for patients at risk of systemic anticholinergic side effects or those seeking a nondaily treatment option,” the researchers said.

Seventy-four patients with urodynamically confirmed detrusor overactivity and persistent symptoms despite at least 2 months of single pharmacotherapy were enrolled in this single-centre, open-label, randomized trial. Participants were randomly allocated to receive onabotulinumtoxinA injection (100 U) or combined pharmacotherapy with solifenacin 5 mg and mirabegron 25 mg.

The researchers assessed voiding parameters, adverse events, and patient-reported outcomes at baseline and 12 weeks using the Urogenital Distress Inventory, Incontinence Impact Questionnaire, and the Overactive Bladder Symptom Score.

Of the 74 patients, 66 completed the study (33 per group). Both treatment regimens resulted in reduced urgency episodes (median of 2.0 per 24 hr at 12 weeks). [J Urol 2025;214:344-353]

The mean between-group difference was ‒0.1 (95 percent confidence interval, ‒1.5 to 1.4; p=0.925), suggesting no significant difference. Both onabotulinumtoxinA and the combined pharmacotherapy improved urinary frequency, nocturia, urge incontinence, and quality-of-life measures, with no significant differences.

On the other hand, onabotulinumtoxin A showed a more favourable safety profile, as the combined pharmacotherapy led to significantly more adverse effects such as dry mouth, constipation, and blurred vision (p<0.05 for all).

“These findings support individualized treatment selection based on patient characteristics and risk tolerance,” the researchers said.

Sensitization

Refractory OAB is partly driven by central sensitization, which involves peripheral afferent nerves, neurotransmitters, the spinal cord, and the brain. This is similar to the mechanism driving somatic syndromes. [Low Urin Tract Symptoms 2019;11:177-181]

“Chronic noxious stimuli can strengthen the synapses involved in nociceptive transmission, ascending from peripheral nerves to the spinal cord and brain,” the researchers said. “On the other hand, the brain can integrate and transmit signals that influence the spinal cord to process nociceptive inputs in a descending manner.” [Ann Neurol 2013;74:630-636]

In previous studies, women with severe OAB symptoms were found to be at greater risk of having somatic symptoms and stronger body pain intensity. [Neurourol Urodyn 2017;36:1113-1118; Medicine (Baltimore) 2017;96:e8266]

“The clinical efficacy of onabotulinumtoxinA is proposed to act through a dual mechanism targeting both the afferent and efferent neuronal pathways of bladder control,” the researchers said.

“OnabotulinumtoxinA blocks the release of acetylcholine and other neurotransmitters, thereby reducing the expression of sensory receptors,” they added. [Eur Urol 2006;49:644-650; Int J Urol 2012;19:202-215]

Guidelines

The 2024 guidelines by the American Urological Association on OAB treatment highlighted the importance of shared decision-making with patients with regard to multiple treatment modalities. [Urol 2024;212:11-20]

“Rather than following a specific treatment sequence, clinicians are encouraged to offer a variety of treatment options,” the researchers said. “Through comprehensive counselling and shared decision-making, a personalized treatment plan can be developed, taking into account the patient’s values, preferences, and treatment goals.”