Oxybutynin Dosage Recommendations
The recommended dosage for oxybutynin in adults is 5 mg orally three times daily for immediate-release formulation, or 10 mg once daily for extended-release formulation, with adjustments based on clinical response and tolerability. 1, 2
Adult Dosing Guidelines
Immediate-Release Formulation
- Starting dose: 2.5-5 mg orally three times daily 3
- Usual effective dose: 5 mg orally three times daily 3, 4
- Low-dose option: 2.5 mg three times daily may provide good efficacy with fewer side effects in patients who cannot tolerate standard dosing 3
- Maximum daily dose: 5 mg four times daily (20 mg/day) 2
Extended-Release Formulation
- Starting dose: 5-10 mg orally once daily 1, 2
- Usual effective dose: 10 mg orally once daily 1, 5
- Dose range: 5-30 mg once daily, offering greater dosing flexibility than immediate-release formulation 2
- Administration: Can be given at bedtime or with the main meal 1
Pediatric Dosing Guidelines
- For children with neurogenic bladder: 0.2 mg/kg three times daily 6
- For nocturnal enuresis: 5 mg at bedtime, which may be increased to 10 mg if needed 6
- Often combined with desmopressin for better efficacy in nocturnal enuresis cases 6
Special Populations
Elderly Patients
- Consider starting at lower doses (2.5 mg two to three times daily for immediate-release) due to increased risk of anticholinergic side effects 3
- Titrate dose based on clinical response and tolerability 2
Renal or Hepatic Impairment
- Consider dose reduction in patients with significant renal or hepatic dysfunction 2
- Monitor closely for adverse effects in these populations 1
Administration Considerations
- Immediate-release tablets can be taken with or without food 3
- Extended-release formulation should be swallowed whole, not crushed or chewed 2
- Extended-release tablets provide smoother plasma concentration profiles and potentially fewer side effects than immediate-release formulation 5, 2
Monitoring and Dose Adjustments
- Assess clinical response after 2-4 weeks of therapy 3
- If efficacy is inadequate and side effects are minimal, dose can be increased 2
- If side effects are problematic, consider reducing the dose or switching to extended-release formulation 1, 3
- For nocturnal enuresis, anti-enuretic effect should appear within 2 months 6
Common Side Effects to Monitor
- Dry mouth (most common): reported in 29% of patients on extended-release and up to 83% on immediate-release 1, 4
- Other common side effects include constipation, blurred vision, drowsiness, and urinary retention 1, 4
- Side effects are generally dose-dependent and may be less pronounced with extended-release formulation 5, 2
Clinical Pearls
- Starting with a lower dose (2.5 mg three times daily) may achieve good efficacy with fewer side effects 3
- Once-daily extended-release formulation may improve patient adherence compared to multiple daily dosing of immediate-release 5, 2
- If dry mouth is intolerable with oxybutynin, consider alternative antimuscarinic medications like solifenacin 4