From the Guidelines
Mirabegron is generally considered more effective than oxybutynin for treating Overactive Bladder (OAB) due to its improved side effect profile and efficacy in reducing urinary incontinence episodes, as demonstrated in recent studies such as the SYNERGY I/II and BESIDE trials 1.
Treatment Considerations
When deciding between oxybutynin and mirabegron for OAB treatment, several factors should be considered, including:
- Patient age and comorbidities
- Other medications and potential interactions
- Side effect tolerance and preferences
- Cost and availability of the medications
Medication Comparison
Oxybutynin, an anti-muscarinic agent, is often associated with side effects such as dry mouth, constipation, and cognitive impairment, particularly in older adults 1. In contrast, mirabegron, a beta-3 adrenergic receptor agonist, tends to have fewer anticholinergic side effects, although it may slightly increase blood pressure 1.
Combination Therapy
For patients who do not respond to monotherapy, combination therapy with an anti-muscarinic agent and a beta-3 adrenergic receptor agonist, such as solifenacin and mirabegron, may be considered, as it has shown improved efficacy in reducing urinary incontinence episodes and micturitions per 24 hours, although it may increase the risk of adverse events such as dry mouth and constipation 1.
Behavioral Modifications
Regardless of the chosen medication, behavioral modifications like timed voiding, fluid management, and pelvic floor exercises should be incorporated into the treatment plan to optimize outcomes and improve quality of life for patients with OAB.
From the Research
Efficacy of Oxybutynin and Mirabegron
- Mirabegron 50 mg was found to be as efficacious as antimuscarinics, including oxybutynin, in reducing the frequency of micturition, incontinence, and urgency urinary incontinence (UUI) episodes 2.
- A systematic review and meta-analysis found that mirabegron 50 mg was effective in treating overactive bladder syndrome, with significant changes in urgency urinary incontinence, total incontinence, and nocturia compared to placebo 3.
- Mirabegron 50 mg was also found to be effective compared to oxybutynin 73.5 mg, with significant changes in overall adverse events favoring mirabegron 50 mg 3.
Safety and Tolerability
- Mirabegron 50 mg had an incidence of dry mouth similar to placebo and significantly lower than all included antimuscarinics, including oxybutynin 2.
- A review of mirabegron for the treatment of overactive bladder found that it had a favorable safety and tolerability profile, particularly compared to antimuscarinics, for dry mouth, constipation, and many CNS effects 4.
- A prospective cohort study found that mirabegron improved clinical and quality of life outcomes in patients with overactive bladder, with a low rate of side effects 5.
Treatment Guidelines
- For overactive bladder patients, starting with antimuscarinic agents is feasible, but mirabegron 50 mg may be a safer and more appropriate option for patients with a risk of cognitive dysfunction, history of constipation, dry mouth, and urinary retention 6.
- In elderly patients with low detrusor contractility, central nervous system lesions, and men with benign prostatic hyperplasia, starting with 25 mg mirabegron is recommended, with the option to increase the dose to 50 mg if necessary 6.