Is Myrbetriq (mirabegron) safe for this patient?

Safety of Mirabegron (Myrbetriq) for an 88-Year-Old Female Patient

Mirabegron (Myrbetriq) is safe for this 88-year-old female patient and is actually preferred over antimuscarinic agents due to its favorable side effect profile, particularly regarding cognitive effects and dry mouth, which is especially important in elderly patients. 1

Patient-Specific Considerations

Current Medications and Interactions

• The patient is currently on:

  • Acetaminophen 500 mg daily
  • Amiodarone 100 mg daily
  • Apixaban 2.5 mg twice daily
  • Citalopram 40 mg daily
  • Dapagliflozin 10 mg daily
  • Diclofenac gel topically twice daily
  • Pantoprazole 40 mg daily
  • Trazodone 50 mg at bedtime (new medication)
  • Valsartan 40 mg twice daily

• Mirabegron is a moderate CYP2D6 inhibitor 2, which could potentially interact with medications metabolized by this pathway

• Of the patient's current medications, trazodone may have some metabolism through CYP2D6, but this interaction is not likely to be clinically significant at the low dose the patient is taking

Dosing Recommendations

• For this 88-year-old patient, the recommended starting dose is 25 mg once daily 1
• The dose could be increased to 50 mg once daily if needed and tolerated after 4-8 weeks 1
• The medication should be taken with food to reduce potential exposure-related risks 1, 2

Renal Considerations

• Given the patient's advanced age (88 years), she likely has some degree of renal impairment
• If the patient has severe renal impairment (eGFR 15-29 mL/min/1.73 m²), the daily dose should not exceed 25 mg 2
• Mirabegron is not recommended for patients with end-stage renal disease (eGFR <15 mL/min/1.73 m²) 2

Safety Profile in Elderly Patients

Advantages Over Antimuscarinics

• Mirabegron has a significantly better side effect profile than antimuscarinic agents, particularly regarding cognitive effects and dry mouth 1
• The incidence of dry mouth with mirabegron is similar to placebo and three to five-fold less than with antimuscarinic agents like tolterodine 3
• This is particularly important for elderly patients, as dry mouth is the most bothersome adverse effect associated with antimuscarinic drugs and often leads to treatment discontinuation 3

Efficacy in Elderly

• High-quality evidence shows that age does not modify clinical outcomes associated with mirabegron treatment for urinary incontinence 1
• Studies have demonstrated that mirabegron provides significant improvements in overactive bladder symptoms in patients ≥65 years of age 3
• The efficacy and safety of mirabegron are not substantially different in older patients compared to younger patients 1, 4

Cardiovascular Safety

• Regular blood pressure monitoring is essential, especially in patients with pre-existing hypertension 1
• Mirabegron can increase blood pressure, but in clinical trials, the mean increase in systolic and diastolic blood pressure at the 50 mg dose was approximately 0.5 to 1 mm Hg greater than placebo 2
• Mirabegron is not recommended for patients with severe uncontrolled hypertension 2

Monitoring Recommendations

1. Blood Pressure: Regular monitoring is essential, especially given the patient's age and use of valsartan for hypertension 1

2. Urinary Retention: Monitor for signs and symptoms of urinary retention, especially since the patient is elderly 1, 2

3. Constipation: Monitor for this potential side effect, although it's less common with mirabegron than with antimuscarinic agents 1

4. Renal Function: Regular assessment of renal function is important given the patient's advanced age 2

Common Adverse Events

The most common adverse events observed with mirabegron in clinical trials include:

• Hypertension
• Nasopharyngitis
• Urinary tract infection 4, 3

These adverse events are generally mild to moderate in severity and do not typically lead to treatment discontinuation.

Conclusion

Mirabegron represents a safe and effective treatment option for this 88-year-old female patient. Its favorable side effect profile compared to antimuscarinic agents makes it particularly suitable for elderly patients. Starting at a dose of 25 mg once daily with food, with appropriate monitoring of blood pressure and renal function, provides the optimal balance of efficacy and safety for this patient.