Antimuscarinic — Overactive Bladder
Pregnancy: Avoid in pregnancy — limited safety data
Trospium Chloride
Brand names: Regurin, Regurin XL
Adult dose
Dose: 20 mg twice daily (immediate release); 60 mg once daily (XL formulation)
Route: Oral
Frequency: Twice daily (IR) or once daily (XL)
Max: 40 mg/day (IR); 60 mg/day (XL)
Take IR formulation on empty stomach (food reduces absorption by 70%). XL formulation taken in the morning. Preferred antimuscarinic in elderly due to lower CNS penetration
Paediatric dose
Dose: Not applicable N/A/kg
Route: Oral
Frequency: Not applicable
Max: Not applicable
Not licensed in children
Dose adjustments
Renal
Reduce to 20 mg once daily if eGFR under 30
Hepatic
Use with caution in hepatic impairment
Paediatric weight-based calculator
Not licensed in children
Clinical pearls
- Quaternary ammonium compound — does not cross the blood-brain barrier; significantly lower cognitive adverse effects and dementia risk compared to tertiary amines (oxybutynin, tolterodine, solifenacin) — preferred in elderly patients
- STOPP v3: tertiary antimuscarinic antimuscarinics are potentially inappropriate in elderly with cognitive impairment; trospium (quaternary) is the exception
- IR formulation must be taken on an empty stomach — absorption reduced by 70-85% with food; a common reason for treatment failure
- If antimuscarinic is needed in a patient with dementia or cognitive impairment, trospium is the safest choice due to minimal CNS penetration
- NICE NG123: Antimuscarinics or mirabegron for OAB — offer patient choice based on individual preferences, comorbidities, and tolerability
Contraindications
- Urinary retention
- Gastric retention
- Uncontrolled narrow-angle glaucoma
- Myasthenia gravis
Side effects
- Dry mouth (common)
- Constipation
- Blurred vision
- Tachycardia
- Urinary retention
- Cognitive effects (significantly less than other antimuscarinics due to quaternary ammonium structure)
Interactions
- Other antimuscarinics (additive effects)
- Metformin, morphine, procainamide (compete for renal tubular secretion — may increase trospium levels)
- Alcohol (increased risk of somnolence with XL)
Monitoring
- OAB symptom scores (ICIQ-OAB)
- Post-void residual (to exclude retention)
- Cognitive function (less concern than other antimuscarinics)
- Bowel function
Reference: BNFc; BNF 90; NICE NG123 (Urinary Incontinence and OAB); STOPP/START v3; EAU OAB Guidelines 2024. Verify against your local formulary and the latest BNF before prescribing.
Related
Curated clinical cross-links plus same-class fallbacks.
Calculators