What is the recommended dose of mirabegron (beta-3 adrenergic agonist) for an elderly patient with impaired renal function?

Mirabegron Dosing for Elderly Patients

For elderly patients (≥65 years), start mirabegron at 25 mg once daily, which can be increased to 50 mg once daily after 4-8 weeks if needed and tolerated. 1, 2

Standard Dosing Approach

• Starting dose: 25 mg once daily for all elderly patients, regardless of whether they have comorbidities 1, 3, 2
• Titration: Increase to 50 mg once daily after 4-8 weeks if symptoms persist and the lower dose is well tolerated 2
• The 25 mg dose has demonstrated both safety and therapeutic efficacy specifically in patients aged ≥80 years with multiple comorbidities 3, 4

Dose Modifications for Renal Impairment

Elderly patients frequently have declining renal function, requiring dose adjustment:

• eGFR 30-89 mL/min/1.73 m²: Start 25 mg daily, maximum 50 mg daily 2
• eGFR 15-29 mL/min/1.73 m²: Start 25 mg daily, maximum remains 25 mg daily (do not increase) 2
• eGFR <15 mL/min/1.73 m² or dialysis: Mirabegron is not recommended 2

Dose Modifications for Hepatic Impairment

• Child-Pugh Class A (mild): Start 25 mg daily, maximum 50 mg daily 2
• Child-Pugh Class B (moderate): Start 25 mg daily, maximum remains 25 mg daily 2
• Child-Pugh Class C (severe): Not recommended 2

Clinical Evidence in Elderly Populations

The 25 mg dose is particularly well-suited for elderly patients:

• A prospective study in patients aged ≥80 years showed significant improvements in voiding symptoms, quality of life, and bladder condition scores after 3 months at 25 mg daily 4
• Adverse events were acceptably low (24.6%) in the elderly cohort, lower than in younger patients 4
• A phase IV study (PILLAR) in patients ≥65 years demonstrated statistically significant improvements in micturitions, incontinence episodes, urgency episodes, and volume voided per micturition with flexible dosing starting at 25 mg 5

Safety Considerations Specific to Elderly

Monitor blood pressure periodically, especially during initial treatment and in patients with hypertension, as mirabegron can cause dose-dependent blood pressure increases 1, 6

• Mirabegron is contraindicated in severe uncontrolled hypertension 6
• The most frequent adverse events are hypertension, urinary tract infections, headache, and nasopharyngitis 6, 7
• Unlike antimuscarinics, mirabegron does not cause significant anticholinergic effects (dry mouth, constipation, cognitive impairment), making it particularly advantageous in elderly patients 7, 8

Administration Instructions

• Swallow tablets whole with water; do not chew, divide, or crush 2
• Can be taken with or without food in adults 2
• If a dose is missed and >12 hours have passed, skip that dose and resume at the usual time 2

Practical Algorithm

1. Assess renal and hepatic function before initiating therapy
2. Start 25 mg once daily in all elderly patients
3. Monitor blood pressure at baseline and periodically during treatment
4. Reassess symptoms at 4-8 weeks: If inadequate response and good tolerability, increase to 50 mg daily (unless contraindicated by renal/hepatic impairment)
5. Do not exceed 25 mg daily if eGFR 15-29 mL/min/1.73 m² or Child-Pugh Class B hepatic impairment 2