In an 80‑year‑old woman taking mirabegron (Myrbetriq) who cannot void, should the drug be discontinued and how should acute urinary retention be managed?

Discontinue Mirabegron Immediately and Manage Acute Urinary Retention

Yes, discontinue Myrbetriq (mirabegron) immediately in this 80-year-old woman who cannot void, as urinary retention is a known adverse effect of this medication, and proceed with urgent bladder decompression via catheterization. 1

Immediate Management Algorithm

Step 1: Discontinue Mirabegron

• Stop the medication immediately—the FDA label explicitly warns that urinary retention has been reported in patients taking mirabegron, particularly in those with bladder outlet obstruction 1
• Do not restart this medication in this patient given the acute retention episode

Step 2: Bladder Decompression

• Insert a urethral catheter immediately to relieve the acute retention
• Measure the post-void residual volume to document the degree of retention
• The 2024 AUA/SUFU guideline emphasizes measuring PVR in patients with inadequate response to OAB treatment 2

Step 3: Short-Term Catheter Management

• Keep the catheter in place for 24-72 hours to allow bladder recovery
• Monitor for hematuria (common after acute retention relief)
• Ensure adequate hydration

Step 4: Trial of Voiding

• After 24-72 hours, perform a voiding trial by removing the catheter
• Measure PVR immediately after the first void
• If PVR remains >200 mL or patient cannot void, consider:
  • Teaching clean intermittent catheterization (CIC)
  • Short-term indwelling catheter with urology referral

Why This Matters in an 80-Year-Old

The FDA label specifically warns about urinary retention risk with mirabegron, particularly in patients with bladder outlet obstruction 1. While studies show mirabegron can be effective and safe in patients over 80 years 3, 4, acute urinary retention represents a contraindication to continuing the medication. The drug-induced retention literature confirms that up to 10% of acute retention episodes may be medication-related, and discontinuation is the primary management strategy 5.

Critical Pitfalls to Avoid

• Do not attempt to restart mirabegron in this patient—the acute retention episode indicates she is not a suitable candidate
• Do not delay catheterization while waiting for spontaneous voiding—prolonged overdistension can cause permanent bladder damage
• Do not assume this is purely age-related—mirabegron is the likely culprit and must be stopped
• Avoid chronic indwelling catheters unless all other options fail, as the AUA/SUFU guideline reserves this only when therapies are contraindicated, ineffective, or no longer desired 2

Alternative OAB Management After Recovery

Once retention resolves:

• Consider behavioral modifications (bladder training, timed voiding)
• If pharmacotherapy needed, antimuscarinics may be considered with extreme caution and close PVR monitoring
• The guideline suggests measuring PVR before any OAB intervention and monitoring for retention symptoms 2
• In this patient's case, given her age and retention history, non-pharmacologic approaches should be prioritized

The evidence is clear: mirabegron-associated urinary retention requires immediate drug discontinuation and catheter drainage 1, 5.