Reduced-Dose OnabotulinumtoxinA for Urgency Incontinence in Older Women: Methods

Older women have a high prevalence of and bother from overactive bladder (OAB) and urgency urinary incontinence (UUI), with unique treatment challenges. It is important to improve care for this long-overlooked and understudied group.

The objective was to describe the design and rationale for a randomized controlled noninferiority trial of low-dose (50 unit) versus standard-dose (100 unit) onabotulinumtoxinA (OnabotA) for OAB symptoms in women 70 years or older with UUI.

Study population, injection procedure, and conduct are described. The primary outcome is change in quality of life (QOL) between groups as measured by the OAB Questionnaire (OABq-SF) 3 months posttreatment, including confirmatory heterogeneity of treatment effect analysis by frailty status. Secondary outcomes include patient-reported symptom bother and distress, satisfaction, goal attainment, depression scores, adverse events (AEs), cost analysis, and qualitative interviews. Patients will be assessed monthly for safety and efficacy through 12 months and can receive up to 2 additional treatments.

A sample size of 278 is needed to achieve 90% power to detect noninferiority. Assuming a withdrawal of 26%, the target randomization is 376 participants. Adult females aged 70 years and older are recruited if they have urgency or urgency-predominant mixed urinary incontinence. Exclusion criteria include postvoid residual volume >150 mL, need for treatment under sedation, current other treatment for OAB, and conditions that affect bladder emptying.

This trial will contribute important data on symptom-specific and health-related QOL, patient-reported and clinical outcomes, and AEs among older women with UUI being treated with the standard dose versus reduced dose of OnabotA.