Burden and Efficacy of Anticholinergic vs Mirabegron in Overactive Bladder - A Randomized Controlled Study (BEAM)

BURDEN AND EFFICACY OF ANTICHOLINERGIC VS MIRABEGRON IN OVERACTIVE BLADDER - A RANDOMIZED CONTROLLED STUDY

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.

Study Overview

• Status: Not yet recruiting
• Conditions: Overactive Bladder (OAB)
• Intervention / Treatment: Drug: Solifencin; Drug: Mirabegron

• Study Type: Interventional
• Enrollment (Estimated): 208
• Phase: Phase 4

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult; Older Adult
• Accepts Healthy Volunteers: No

Description

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.

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Treatment
• Allocation: Randomized
• Interventional Model: Parallel Assignment
• Masking: None (Open Label)

Number of Arms

4

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Low Anticholinergic Burden - Solifenacin; Participants randomized to this arm 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.	Drug: Solifencin; 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.
Active Comparator: Low Anticholinergic Burden - Mirabegron; 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.	Drug: Mirabegron; 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.
Active Comparator: High Anticholinergic Burden - Mirabegron; 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.	Drug: Mirabegron; 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.
Experimental: High Anticholinergic Burden - Solifenacin; Participants randomized to this arm 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.	Drug: Solifencin; 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.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
ICIQ OAB	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).	From enrollment to 4 and 8 weeks

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Responder rate at Month 2	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.	From enrollment to 8 weeks
Change in frequency-volume chart parameters at Month 2	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.	From enrollment to 8 weeks
Treatment discontinuation rate	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.	From enrollment to the end of 8 weeks
Incidence of adverse events	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.	From enrollment to the end of 8 weeks

Other Outcome Measures

Outcome Measure	Measure Description	Time Frame
Treatment-by-DBI-stratum interaction on ICIQ-OAB change at Month 2	This exploratory analysis examines whether the difference in effectiveness between the two treatments depends on a participant's baseline anticholinergic burden - that is, whether one treatment works comparatively better in the high-burden group (DBI ≥ 1) and the other in the low-burden group (DBI < 1). It is assessed by testing the statistical interaction between treatment arm and DBI stratum for the change in ICIQ-OAB total score at 2 months. This analysis is hypothesis-generating only; the study is not designed with sufficient statistical power to confirm such an interaction.	From enrollment to the end of 8 weeks

Collaborators and Investigators

• Sponsor: Universidade do Porto
• Collaborators: Unidade Local de Saúde São João

Study record dates

Study Major Dates

• Study Start (Estimated): July 1, 2026
• Primary Completion (Estimated): July 1, 2027
• Study Completion (Estimated): August 1, 2027

Study Registration Dates

• First Submitted: July 13, 2026
• First Submitted That Met QC Criteria: July 13, 2026
• First Posted (Actual): July 17, 2026

Study Record Updates

• Last Update Posted (Actual): July 17, 2026
• Last Update Submitted That Met QC Criteria: July 13, 2026
• Last Verified: June 1, 2026

More Information

Terms related to this study

• Keywords: Overactive bladder; Anticholinergic burden
• Additional Relevant MeSH Terms: Urogenital Diseases; Male Urogenital Diseases; Urologic Diseases; Female Urogenital Diseases; Female Urogenital Diseases and Pregnancy Complications; Lower Urinary Tract Symptoms; Urological Manifestations; Urinary Bladder Diseases; Pathological Conditions, Signs and Symptoms; Signs and Symptoms; Urinary Bladder, Overactive; mirabegron
• Other Study ID Numbers: BEAM

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No
• product manufactured in and exported from the U.S.: No