Bladder Relaxing Medications
Antimuscarinic medications (such as oxybutynin, tolterodine, solifenacin, darifenacin, fesoterodine, and trospium) and beta-3 adrenergic agonists (such as mirabegron) are the primary bladder relaxing medications used to treat overactive bladder. 1
Antimuscarinic Medications
These medications work by blocking acetylcholine at muscarinic receptors in the bladder, preventing involuntary contractions and relaxing the detrusor muscle:
Specific Examples:
Oxybutynin chloride exerts a direct antispasmodic effect on smooth muscle and inhibits the muscarinic action of acetylcholine, thereby relaxing bladder smooth muscle and increasing bladder capacity 2
Solifenacin has the lowest risk for discontinuation due to adverse effects among antimuscarinics and effectively improves urgency urinary incontinence 1
Tolterodine improves storage symptoms and has risks for discontinuation due to adverse effects similar to placebo 1
Darifenacin also has discontinuation rates similar to placebo 1
Fesoterodine achieves continence more effectively than tolterodine 3
Trospium effectively improves urinary incontinence and quality of life 3
Beta-3 Adrenergic Agonist
- Mirabegron is recommended as a first-choice alternative due to its efficacy comparable to antimuscarinics but with significantly lower incidence of anticholinergic side effects and lower risk of cognitive effects, particularly important in elderly patients 3
Important Clinical Considerations
Side Effect Profile:
Common antimuscarinic side effects include dry mouth, constipation, and blurred vision 1
Antimuscarinics are associated with increased risk of dementia and cognitive impairment, which may be cumulative and dose-dependent 1
Mirabegron causes nasopharyngitis and gastrointestinal disorders but avoids anticholinergic effects 1
Contraindications and Cautions:
Use antimuscarinics with extreme caution in patients with narrow-angle glaucoma, impaired gastric emptying, or history of urinary retention 1
Consider potential cognitive risks in all patient populations when prescribing antimuscarinics for chronic use 1
Treatment Selection Algorithm:
First-line pharmacologic choice: Beta-3 agonists (mirabegron) are typically preferred before antimuscarinics 1
Second-line options: If mirabegron is ineffective or contraindicated, consider solifenacin or tolterodine based on their favorable adverse effect profiles 3
Base medication choice on tolerability, adverse effect profile, ease of use, and cost 1