Related Experiment Video
Updated: Mar 8, 2026
Bladder Smooth Muscle Strip Contractility as a Method to Evaluate Lower Urinary Tract Pharmacology
Published on: August 18, 2014
Efficacy and Adherence of Flexibly Adding on a Second Antimuscarinic Agent for Patients with Refractory Overactive
Chung-Cheng Wang1,2, Yuan-Hong Jiang3, Hann-Chorng Kuo3
1Department of Urology, En Chu Kong Hospital, College of Medicine, National Taiwan University, New Taipei, Taiwan.
Objectives:
To evaluate the efficacy and adverse events (AE) of flexibly adding on oxybutynin ER in patients with overactive bladder (OAB) refractory to monotherapy with the first muscarinic antagonist.
Methods:
A total of 129 patients with refractory OAB were enrolled in a prospective, open-label protocol. Inclusion criteria were persistent symptoms or partial response to 3-month behavioral therapy and an optimized dose of one antimuscarinic agent. At baseline, weeks 4, and 12 after the oxybutynin ER (5-15 mg once a day) was flexibly added, we assessed the OAB symptom indexes and Patient Perception of Bladder Condition, uroflowmetry, and post-void residual, along with the therapeutic effect, AE, and tolerability. Patients continuing combined antimuscarinic therapy were followed up to 12 months.
Results:
Compared with baseline, all OAB symptom indexes significantly decreased at all visits. A total of 32 (24.8%) and 25 (19.4%) patients reported successful therapeutic effect at weeks 4 and 12, respectively. Twenty-four (18.6%) and 44 (34.1%) patients discontinued therapy at weeks 4 and 12, respectively. Only 31 (24.0%) patients continued the combined medication for up to 12 months. Discontinuation of the combined medication was noted in 28 (21.7%) patients due to AE and in 70 (54.3%) due to lack of efficacy.
Conclusions:
Flexibly adding on a second antimuscarinic agent is effective and safe for only some OAB patients dissatisfied with the first antimuscarinic treatment in the short-term period. The patients' dropout rate is high and the long-term efficacy of the combination of two antimuscarinic agents is limited.
Insights
Adding oxybutynin ER to antimuscarinic monotherapy offers short-term overactive bladder (OAB) relief for some patients. However, high discontinuation rates due to adverse events and lack of efficacy limit long-term benefits.
Area of Science:
- Urology
- Pharmacology
Background:
- Overactive bladder (OAB) is a common condition impacting quality of life.
- Antimuscarinic monotherapy is a first-line treatment for OAB.
- Some patients remain refractory or have partial response to initial antimuscarinic treatment.
Purpose of the Study:
- To assess the efficacy and safety of adding oxybutynin extended-release (ER) to existing antimuscarinic monotherapy in OAB patients.
- To evaluate patient-reported outcomes, urodynamic parameters, and adverse events.
Main Methods:
- Prospective, open-label study of 129 OAB patients with refractory symptoms.
- Flexible dosing of oxybutynin ER (5-15 mg/day) added to optimized antimuscarinic monotherapy.
- Assessment of OAB symptom indexes, Patient Perception of Bladder Condition, uroflowmetry, and post-void residual at baseline, 4, and 12 weeks. Follow-up to 12 months for those continuing therapy.
Main Results:
- Significant reduction in OAB symptom indexes observed at all visits compared to baseline.
- Therapeutic effect reported by 24.8% at 4 weeks and 19.4% at 12 weeks.
- High discontinuation rates: 18.6% at 4 weeks and 34.1% at 12 weeks, primarily due to adverse events (21.7%) and lack of efficacy (54.3%).
Conclusions:
- Flexible addition of oxybutynin ER provides short-term efficacy for select OAB patients refractory to monotherapy.
- High patient dropout rates and limited long-term efficacy of dual antimuscarinic therapy are significant concerns.
- This approach may be suitable for specific patient subgroups in the short term, but long-term management requires careful consideration.
Related Concept Videos
01:24Cholinergic Antagonists: Pharmacokinetics
01:26Cholinergic Antagonists: Therapeutic Uses
Respiratory Tract: Ipratropium, aclidinium, and tiotropium treat asthma, chronic bronchitis, and chronic obstructive pulmonary disease (COPD). They protect against bronchoconstriction caused by irritants like cigarette smoke, sulfur dioxide, and ozone. They also help reduce nasopharyngeal...
01:28Cholinergic Antagonists: Pharmacological Actions
Gastrointestinal Effects: Antimuscarinics reduce gut contractions, increase gastric emptying, and slow intestinal transit. They partly inhibit gastric acid secretion...
01:20Antiasthma Drugs: Muscarinic Receptor Antagonists
Antimuscarinic agents compete with ACh for the same binding site on the muscarinic receptors. By binding to these receptors, they inhibit the downstream effects of ACh and block the parasympathetic...
01:21Drugs for Treatment of Constipation-Predominant IBS
00:59Direct-Acting Cholinergic Agonists: Pharmacological Actions