A Phase 4 interventional study of Solifencin and Mirabegron in Overactive Bladder (OAB), sponsored by Universidade do Porto. Not yet recruiting. Open to participants aged 18 Years and older. Per ClinicalTrials.gov, last updated 2026-07-17.
Sponsored by Universidade do Porto · Phase 4, Interventional, and Treatment
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.
858 studies on the registry are indexed under Urinary Bladder, Overactive; 127 are open to participants now.
This study's planned enrollment of 208 is above the median of 70 across 649 interventional studies indexed under Urinary Bladder, Overactive.
Browse Urinary Bladder, Overactive studies →Universidade do Porto is the lead sponsor of 174 studies on the registry; 53 are open to participants now.
Counted across the registry records on this site, refreshed daily.
Go through the criteria one by one — yes, no or not sure — and take the list to your doctor or the study team. Kept in this browser only.
Exclusion Criteria:
Neurogenic bladder.
Underlined terms in the criteria open these too. Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Before you join, the study team explains what taking part involves — its purpose, what happens, the risks and possible benefits — and answers your questions, so you can decide freely. Consent is usually recorded on a form (the informed consent form, ICF) signed by you or, where the law allows, by someone legally authorised to decide for you.
You can keep asking questions during the study, you are told of new information that matters, and you can choose to leave at any time.
Judged by the study doctor to matter for your health or for the study. It is a doctor’s decision, so ask the study team if you are unsure whether something counts.
A reason a treatment, test or procedure should not be given to a particular person, such as an allergy, another illness or a medicine they take.
Informed consent
Before you join, the study team explains what taking part involves — its purpose, what happens, the risks and possible benefits — and answers your questions, so you can decide freely. Consent is usually recorded on a form (the informed consent form, ICF) signed by you or, where the law allows, by someone legally authorised to decide for you.
You can keep asking questions during the study, you are told of new information that matters, and you can choose to leave at any time.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Clinically significant
Judged by the study doctor to matter for your health or for the study. It is a doctor’s decision, so ask the study team if you are unsure whether something counts.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Contraindication
A reason a treatment, test or procedure should not be given to a particular person, such as an allergy, another illness or a medicine they take.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
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
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.
Drug: Mirabegron
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.
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.
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).
Time frame: From enrollment to 4 and 8 weeks
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.
Time frame: 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.
Time frame: 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.
Time frame: 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.
Time frame: From enrollment to the end of 8 weeks
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.
Time frame: From enrollment to the end of 8 weeks
No study locations are listed for this record.
Start is estimated for Jul 2026; primary completion for Jul 2027, 12 months later.
Of 42 non-industry phase 4 interventional studies under Urinary Bladder, Overactive, half reached primary completion within 29 months of starting (the median), counting those still running; a quarter within 18 and three quarters within 51. This study's planned 12 months is below that.
Counting every sponsor, half of 54 studies reached it within 23 months; a quarter within 15 and three quarters within 48.
How these figures are worked out, and which studies are left out of them.
This study is not yet recruiting, as verified in Jun 2026. You cannot join it, but the record below documents what was studied.
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