Can Myrbetriq (mirabegron) be prescribed for a 74-year-old female with primary progressive multiple sclerosis (MS) experiencing urinary incontinence and overactive bladder (OAB)?

Mirabegron for Urinary Incontinence and OAB in a 74-Year-Old Female with Primary Progressive Multiple Sclerosis

Mirabegron (Myrbetriq) is an appropriate treatment option for this 74-year-old female with primary progressive multiple sclerosis (MS) experiencing urinary incontinence and overactive bladder (OAB). It offers a favorable safety profile compared to antimuscarinic medications, particularly regarding cognitive side effects, which is especially important in elderly patients with neurological conditions.

Treatment Rationale and Algorithm

1. First-line approach for neurogenic OAB in MS patients:

   • Begin with mirabegron 25 mg daily as initial therapy
   • Monitor blood pressure before starting and during treatment
   • After 4-8 weeks, dose can be increased to 50 mg if needed and tolerated 1

2. If inadequate response to mirabegron monotherapy:

   • Consider combination therapy with mirabegron plus an antimuscarinic (preferably solifenacin 5 mg)
   • Combination therapy has shown improved efficacy with additive effects for urgency urinary incontinence episodes, urgency episodes, and nocturia 2
   • Recent evidence specifically supports this combination in MS patients with OAB 3

Evidence Supporting Mirabegron in MS Patients

Mirabegron has demonstrated efficacy in MS patients with neurogenic detrusor overactivity:

• A 2020 study comparing mirabegron to solifenacin in MS patients found that approximately 70% of patients in both groups achieved clinically important improvement in OAB symptoms 4
• While solifenacin showed greater symptom improvement, mirabegron demonstrated better bowel function outcomes with improvement in constipation scores, whereas solifenacin worsened constipation in 30% of patients 4
• A 2017 study showed that combination therapy with mirabegron and desmopressin was effective in MS patients with neurogenic detrusor overactivity who had inadequate response to antimuscarinic therapy 5

Advantages of Mirabegron in Elderly Patients

For this 74-year-old patient, mirabegron offers several advantages:

• The PILLAR study specifically demonstrated efficacy, safety, and tolerability of mirabegron in patients aged ≥65 years with OAB and incontinence 6
• Mirabegron has a significantly lower risk of cognitive side effects compared to antimuscarinic medications, which is particularly important in elderly patients and those with neurological conditions 1
• Lower incidence of dry mouth and constipation compared to antimuscarinic medications, potentially improving medication adherence 1

Precautions and Monitoring

1. Blood pressure monitoring:

   • Mirabegron can increase blood pressure
   • Perform baseline blood pressure measurement before starting treatment
   • Regular monitoring during treatment, especially in patients with pre-existing hypertension
   • Not recommended in severe uncontrolled hypertension 7

2. Urinary retention:

   • Monitor for signs and symptoms of urinary retention
   • Use with caution in patients with bladder outlet obstruction
   • Use with caution when combined with antimuscarinic medications 7

3. Drug interactions:

   • Mirabegron is a moderate CYP2D6 inhibitor
   • Monitor for potential interactions with medications metabolized by CYP2D6 7

Practical Recommendations

• Start with mirabegron 25 mg daily
• Assess response after 4-8 weeks
• If inadequate response, increase to 50 mg daily or consider adding solifenacin 5 mg
• Monitor for adverse effects, particularly blood pressure changes and urinary retention
• Regular follow-up to assess efficacy and tolerability

Common Pitfalls to Avoid

1. Starting with too high a dose in elderly patients
2. Failing to monitor blood pressure before and during treatment
3. Not considering potential drug interactions with other medications the patient may be taking
4. Overlooking the need for regular reassessment of treatment efficacy and side effects
5. Not considering combination therapy if monotherapy provides inadequate symptom relief

By following this approach, mirabegron can be safely and effectively used to manage urinary incontinence and OAB symptoms in this 74-year-old female with primary progressive MS, potentially improving her quality of life while minimizing adverse effects.