Overactive Bladder (OAB)
Conditions
Keywords
Overactive bladder, Anticholinergic burden
Brief summary
Overactive bladder (OAB) is a common condition that causes a sudden, strong need to urinate, often with frequent daytime and night-time trips to the toilet, and sometimes leaking. It can have a substantial impact on everyday quality of life. Two of the most common medicines used to treat OAB work in different ways: one type (antimuscarinics, such as solifenacin) blocks a nerve signal in the bladder, while another type (beta-3 agonists, such as mirabegron) helps the bladder muscle relax. Many people with OAB are already taking other medicines - for example, for mood, sleep, or allergies - that, without being intended for the bladder, also block that same nerve signal. The combined effect of all these medicines is called the "anticholinergic burden." Researchers want to understand whether a person's existing anticholinergic burden changes how well each OAB treatment works. The idea is that if this nerve pathway is already heavily blocked by other medicines, an antimuscarinic might be less helpful, and a treatment that works in a different way (mirabegron) might be a better choice. In this study, adults with newly diagnosed OAB who have not yet been treated will be randomly assigned to take either solifenacin or mirabegron once a day. Before starting, each participant's anticholinergic burden will be measured using a validated tool called the Drug Burden Index (DBI) and ACB. Bladder symptoms will be assessed with a standard questionnaire (ICIQ-FLUTS) and a bladder diary at the start of treatment and again after 1 and 2 months. By comparing how participants respond depending on their baseline anticholinergic burden, the study aims to learn whether measuring this burden can help doctors choose the most effective first-line treatment for each patient.
Interventions
DRUGSolifencin
Patients will receive solifenacin succinate 5 mg, an oral selective M3 antimuscarinic, taken once daily for 2 months. Solifenacin reduces overactive bladder symptoms by blocking muscarinic receptor-mediated detrusor contractions.
DRUGMirabegron
Participants randomized to this arm receive mirabegron 50 mg, an oral β3-adrenergic agonist, taken once daily for 2 months. Mirabegron relieves overactive bladder symptoms through a non-anticholinergic mechanism, promoting detrusor relaxation during the storage phase.
Sponsors
Universidade do Porto
Unidade Local de Saúde São João
Study design
Allocation
RANDOMIZED
Intervention model
PARALLEL
Primary purpose
TREATMENT
Masking
NONE
Eligibility
Sex/Gender
ALL
Age
18 Years to No maximum
Healthy volunteers
No
Inclusion criteria
* Adult patients with a clinical diagnosis of overactive bladder syndrome. * Treatment-naïve for OAB pharmacotherapy (no prior antimuscarinic or mirabegron for OAB). * Able to complete the ICIQ-OAB questionnaire and a frequency-volume chart. * Written informed consent.
Exclusion criteria
* Neurogenic bladder. * Previous treatment with anticholinergics or mirabegron for OAB. * History of pelvic radiotherapy or bladder cancer. * Post-void residual volume \> 200 mL. * Clinically significant stress urinary incontinence. * Chronic pelvic pain syndrome. * Congenital urinary tract malformations. * Prior bladder surgery; history of mid-urethral sling or prostate surgery. * Contraindication to solifenacin or mirabegron. * End-stage renal disease on dialysis.
Design outcomes
Primary
| Measure | Time frame | Description |
|---|---|---|
| ICIQ OAB | From enrollment to 4 and 8 weeks | This measure captures how much overactive bladder symptoms change after two months of treatment. The ICIQ-OAB (International Consultation on Incontinence Questionnaire - Overactive Bladder) is a validated, patient-completed questionnaire covering the core symptoms of the condition: daytime urinary frequency, night-time urination (nocturia), urgency, and urgency-related leakage. The four symptom items are summed into a total score ranging from 0 to 16, where a higher score means more severe symptoms. Participants complete the questionnaire at the start of treatment (baseline) and again at 2 months; the outcome is the change between these two time points, with a larger reduction indicating greater symptom improvement. The two treatment arms are compared using an analysis of covariance (ANCOVA) adjusted for each participant's baseline score, performed separately within the high anticholinergic burden group (Drug Burden Index ≥ 1) and the low burden group (DBI \< 1). |
Secondary
| Measure | Time frame | Description |
|---|---|---|
| Responder rate at Month 2 | From enrollment to 8 weeks | This measure reports the proportion of participants who achieve a clinically meaningful improvement in symptoms. A participant is classified as a "responder" if their ICIQ-OAB total score falls by at least 3 points from baseline to 2 months - a reduction generally regarded as noticeable and worthwhile to patients. The outcome is the percentage of responders in each treatment arm. |
| Change in frequency-volume chart parameters at Month 2 | From enrollment to 8 weeks | A frequency-volume chart (bladder diary) is a record that participants keep at home, noting the time and volume of each urination over a defined period. From this diary, three parameters are measured at baseline and at 2 months, and the change between them is reported: (1) the number of urinations per 24 hours; (2) the number of night-time urination episodes (nocturia); and (3) the average volume passed per urination (in millilitres). Fewer urinations and fewer nocturia episodes, together with a larger average voided volume, indicate symptom improvement. |
| Treatment discontinuation rate | From enrollment to the end of 8 weeks | This measure reports the proportion of participants in each arm who stop their assigned treatment before completing the 2-month study period, for any reason (for example, side effects, lack of benefit, or personal choice). It is expressed as a percentage of participants randomized to that arm and serves as an indicator of how well each treatment is tolerated and accepted in practice. |
| Incidence of adverse events | From enrollment to the end of 8 weeks | This measure records the number and type of adverse events - any unwanted or harmful medical occurrence reported by participants or observed by the study team - during treatment. Adverse events are collected at each follow-up visit through 2 months and summarized by arm, including the proportion of participants experiencing at least one event. This outcome describes the safety and tolerability profile of each treatment. |
Outcome results
None listed