What is the best course of action for an elderly female patient, one week post knee surgery, experiencing no urge to void and urinary retention while taking trospium (antimuscarinic) nightly?

Immediate Discontinuation of Trospium Required

Discontinue trospium immediately—this antimuscarinic medication is directly causing the urinary retention and lack of urge to void in this postoperative patient. 1

Understanding the Problem

This patient is experiencing iatrogenic urinary retention from trospium, an antimuscarinic agent that blocks bladder muscarinic receptors and impairs detrusor muscle contraction. 1, 2 The FDA drug label explicitly lists "trouble emptying the bladder" as a contraindication and known adverse effect of trospium. 1

Why Trospium is Causing This Problem

• Trospium's mechanism of action directly inhibits bladder contraction by blocking muscarinic M2 and M3 receptors in the detrusor muscle 2
• Urinary retention occurred in 0.5% of patients in clinical trials, leading to discontinuation 1
• The drug is contraindicated in patients with "trouble emptying the bladder" 1
• Postoperative patients are already at elevated risk for urinary retention due to anesthesia effects, opioid use, and immobility 3

Immediate Management Steps

Step 1: Stop Trospium Tonight

Do not give another dose of trospium. 1 The medication is directly causing the retention and continuing it will worsen the problem and potentially lead to bladder overdistension, infection, or renal complications. 3

Step 2: Assess Bladder Volume and Catheterize if Needed

• Perform bladder scan or ultrasound to measure post-void residual volume 3
• If residual volume >300-400 mL or patient is symptomatic with distension, perform intermittent or indwelling catheterization 3
• Acute urinary retention requires immediate decompression to prevent bladder injury 3

Step 3: Identify Other Contributing Medications

Review the medication list for other drugs that impair bladder emptying: 3

• Opioids (commonly used post-knee surgery)—reduce if possible, use multimodal analgesia
• Benzodiazepines—avoid or minimize
• Other anticholinergics—discontinue all non-essential agents
• Alpha-agonists—review decongestants or vasopressors

Elderly patients are at particularly high risk because multiple medications compound anticholinergic burden. 4, 3

Why Trospium Was Inappropriate for This Patient

Trospium should never have been prescribed for this clinical scenario. The American College of Physicians guidelines address urinary incontinence, not retention. 5 This patient has:

• Urinary retention (inability to empty bladder)
• No urge to void (loss of bladder sensation)

These are opposite problems from overactive bladder/urgency incontinence, which is what trospium treats. 1, 2

The Correct Indication for Trospium

Trospium is indicated for: 1

• Overactive bladder with urgency (strong sudden need to void)
• Urge incontinence (leaking due to inability to delay voiding)
• Frequency (voiding too often)

This patient has none of these symptoms—she cannot void at all. 1

Expected Recovery Timeline

• Trospium has a half-life of approximately 20 hours in elderly patients 2
• Peak plasma concentrations occur 5-6 hours after dosing 2
• Expect gradual return of bladder function over 24-48 hours after discontinuation 2
• If retention persists beyond 48-72 hours after stopping trospium, investigate other causes (prostatic obstruction in males, pelvic organ prolapse, neurogenic bladder from surgery/anesthesia) 3

Critical Pitfall to Avoid

Do not add another medication to "treat" the retention while continuing trospium. 3 Some clinicians mistakenly try to add bethanechol (a cholinergic agonist) to counteract antimuscarinic effects, but this is ineffective and potentially dangerous. 3 The only correct approach is to stop the offending agent. 3

Monitoring After Trospium Discontinuation

• Monitor post-void residual volumes daily until <100-150 mL 3
• Assess for return of normal voiding sensation and urge 3
• If intermittent catheterization is required, continue until spontaneous voiding resumes with acceptable residuals 3
• Watch for urinary tract infection, which occurs in up to 19% of post-stroke patients with voiding dysfunction and is likely similar in postoperative patients 5

Long-Term Considerations

If this patient was prescribed trospium for genuine overactive bladder symptoms prior to surgery, it should have been held perioperatively and can only be restarted once: 3

• Normal voiding function has returned
• Post-void residuals are <100 mL
• Patient has regained normal bladder sensation
• All other contributing medications (especially opioids) have been discontinued

However, given the current presentation of "no urge to void," trospium was likely never appropriate for this patient. 1