Side Effects of Trospium
Trospium causes anticholinergic side effects with dry mouth and constipation being most common, along with dizziness as a distinguishing feature compared to other antimuscarinics, and has a moderate risk of treatment discontinuation due to adverse effects. 1
Most Common Side Effects
The antimuscarinic class effects that occur with trospium include: 1, 2
- Dry mouth - most frequently reported anticholinergic effect 1, 2
- Constipation - second most common side effect 1, 2
- Blurred vision - typical antimuscarinic effect 1
- Dizziness - notably more frequent with trospium compared to oxybutynin 1
Less Common but Important Side Effects
Additional adverse effects that may occur include: 2, 3
- Dyspepsia (occurs in >1% of patients) 3
- Abdominal pain (occurs in >1% of patients) 3
- Nausea (occurs in >1% of patients) 3
- Trouble emptying the bladder (urinary retention risk) 2
- Drowsiness - may impair ability to drive or operate machinery 2
Serious Adverse Effects
Heat prostration can occur due to decreased sweating when trospium is used in hot environments - this is a potentially serious complication requiring patient counseling. 2
Allergic reactions may be serious and include swelling of face, lips, throat, or tongue requiring immediate emergency medical attention. 2
Quantified Risk Profile
The American College of Physicians guideline provides specific risk quantification: 1
- Number needed to harm (NNTH): 8 [CI, 6 to 11] - meaning for every 8 patients treated with trospium, one will experience an adverse effect compared to placebo (moderate-quality evidence) 1
- Discontinuation NNTH: 56 [CI, 30 to 228] - for every 56 patients treated, one will discontinue due to adverse effects compared to placebo (high-quality evidence) 1
Comparative Tolerability Context
Trospium's adverse effect profile positions it in the middle range among antimuscarinics: 1
- Better tolerated than: Oxybutynin (NNTH for discontinuation: 16) and fesoterodine (NNTH: 33) 1
- Less well tolerated than: Tolterodine and darifenacin (both had discontinuation rates similar to placebo) 1
- Distinguishing feature: Dizziness is reported more frequently with trospium than with oxybutynin, while oxybutynin causes more dry mouth and insomnia 1
Special Population Considerations
Patients on polypharmacy: Those receiving 7 or more concomitant medications experience more adverse effects with trospium than those on fewer medications. 1
Renal impairment: Dose adjustment needed in severe renal impairment (creatinine clearance <30 mL/min) as trospium undergoes 70% renal excretion, which may increase adverse effect risk. 4
Clinical Implications for Adverse Effect Management
The extended-release once-daily formulation (60 mg) demonstrates: 5
- Dry mouth rate: 8.7% vs placebo 3% 5
- Constipation rate: 9.4% vs placebo 1.3% 5
- Headache rate: 1.0% vs placebo 2.6% (notably low) 5
- Central nervous system effects are rare due to trospium's quaternary amine structure preventing blood-brain barrier penetration 3, 4
Key Contraindications Based on Adverse Effect Profile
Do not use trospium in patients with: 2
- Urinary retention or trouble emptying bladder
- Delayed gastric emptying
- Uncontrolled narrow-angle glaucoma
- Known hypersensitivity to trospium
Important Drug Interaction Considerations
Alcohol: Must avoid within 2 hours of taking trospium extended-release formulation. 2
Food: Take on empty stomach or at least 1 hour before meals as food reduces bioavailability to 26% of fasting levels, potentially affecting both efficacy and adverse effect profile. 2, 4
Minimal drug interactions: Trospium undergoes negligible cytochrome P450 metabolism, resulting in few metabolic drug interactions. 3, 4