What are the next steps in managing urinary incontinence in an 88-year-old woman with complete bladder emptying, unresponsive to Myrbetriq (mirabegron) 25mg for 6 months?

Management of Refractory Urinary Incontinence in an 88-Year-Old Woman

Switch from mirabegron to an antimuscarinic medication (such as tolterodine or solifenacin) after ensuring bladder training has been attempted, as this patient has failed beta-3 agonist therapy and requires escalation to alternative pharmacologic treatment for urgency incontinence. 1

Initial Assessment and Classification

Before changing therapy, clarify the type of incontinence this patient has:

• Complete bladder emptying with no control suggests urgency urinary incontinence (UUI) rather than overflow incontinence 1
• Rule out reversible causes: urinary tract infection, glycosuria (if diabetic), fecal impaction, medications causing incontinence 1
• Confirm post-void residual is not elevated (>100 mL would suggest retention/overflow) 1

Why Mirabegron Failed

Mirabegron 25 mg is a subtherapeutic dose for most patients:

• The standard effective dose is 50 mg daily 2, 3
• At 25 mg, mirabegron shows poor effectiveness, preventing only one incontinence episode every 2 days on average 4
• However, given 6 months of treatment failure, even at a low dose, switching medication classes is more appropriate than dose escalation at this point 1

Recommended Treatment Algorithm

Step 1: Ensure Non-Pharmacologic Therapy Has Been Attempted

• Bladder training is the recommended first-line treatment for urgency incontinence and should be implemented if not already done 1
• If the patient is obese, weight loss and exercise should be recommended 1
• These interventions are effective, have minimal adverse effects, and are cheaper than medications 1

Step 2: Switch to Antimuscarinic Therapy

Pharmacologic treatment is indicated when bladder training has been unsuccessful 1:

• Tolterodine or solifenacin are preferred choices due to lower discontinuation rates from adverse effects compared to oxybutynin 1
• Solifenacin specifically has the lowest risk for discontinuation due to adverse effects among antimuscarinics 1
• Darifenacin and tolterodine have adverse effect profiles similar to placebo 1

Step 3: Consider Combination Therapy if Monotherapy Fails

If antimuscarinic monotherapy provides insufficient benefit after 4-8 weeks:

• Adding mirabegron 50 mg to solifenacin 5 mg is superior to increasing solifenacin alone and is well-tolerated 2
• This combination approach is evidence-based for patients remaining incontinent on antimuscarinic monotherapy 2

Critical Considerations for This 88-Year-Old Patient

Geriatric-Specific Concerns

• Cognitive impairment screening is essential as unrecognized cognitive issues interfere with medication compliance and self-management 1
• Polypharmacy review is mandatory - identify medications that may worsen incontinence (diuretics, sedatives, anticholinergics from other sources) 1
• Antimuscarinic adverse effects (dry mouth, constipation, blurred vision, cognitive impairment) may be poorly tolerated in elderly patients 1

Medication Selection Based on Tolerability

Base the choice on tolerability, adverse effect profile, ease of use, and cost 1:

• Avoid oxybutynin due to highest discontinuation rates from adverse effects 1
• Extended-release formulations may improve tolerability
• Monitor for anticholinergic burden, especially concerning in elderly patients at risk for delirium or falls

Third-Line Options if Second-Line Fails

If antimuscarinic therapy (with or without mirabegron combination) fails after adequate trial:

• Posterior tibial nerve stimulation (PTNS) may be offered in carefully selected patients willing to comply with weekly 30-minute office visits for 12 weeks 1
• IntradetrusorbotulinumtoxinA may be considered, but requires patient ability and willingness to perform self-catheterization if urinary retention develops 1
• At 88 years old, the patient's functional status, cognitive ability, and caregiver support must be carefully assessed before pursuing these options 1

What NOT to Do

• Do not use indwelling catheters except as absolute last resort due to high risk of infections, urethral erosion, and urolithiasis 1
• Do not pursue surgical options (augmentation cystoplasty, urinary diversion) - these carry substantial risks and are rarely appropriate for non-neurogenic OAB 1
• Do not treat if this is asymptomatic bacteriuria - confirm the patient has true symptomatic incontinence, not just positive urine cultures 5

Follow-Up Strategy

• Reassess at 4-8 weeks to evaluate compliance, efficacy, and adverse effects 1
• Encourage persistence with treatment for this duration to identify responders 1
• If inadequate response or intolerable adverse effects, present alternative treatment options 1
• Consider caregiver burden - effective treatment significantly reduces caregiver stress 6