What are the recommendations for prescribing Myrbetriq (mirabegron) to a patient who just had an uncomplicated Escherichia coli (E. coli) urinary tract infection (UTI)?

Prescribing Mirabegron After E. coli UTI

Mirabegron can be safely prescribed after completion of appropriate antibiotic treatment for an uncomplicated E. coli UTI, provided the infection has fully resolved and a follow-up urine culture confirms eradication of the pathogen.

Mechanism of Action of Mirabegron

Mirabegron (Myrbetriq) is a β3-adrenoceptor agonist that works by:

• Selectively stimulating β3-adrenoreceptors in the detrusor muscle 1
• Causing relaxation of the detrusor muscle during the storage phase of the urinary cycle
• Improving bladder capacity and reducing symptoms of overactive bladder (OAB) 2
• Acting through a different mechanism than antimuscarinic agents commonly used for OAB 2

Post-UTI Prescribing Protocol

Step 1: Confirm Complete Resolution of UTI

• Ensure patient has completed the full course of appropriate antibiotic therapy
• Verify resolution of all UTI symptoms (dysuria, frequency, urgency)
• Consider follow-up urine culture in patients with:
  • Symptoms that did not resolve or recurred within 4 weeks after treatment
  • Atypical presentation
  • High risk for complications 3

Step 2: Assess for Contraindications to Mirabegron

• Hypersensitivity to mirabegron or any inactive ingredients 4
• Severe uncontrolled hypertension (systolic ≥180 mmHg and/or diastolic ≥110 mmHg) 4
• Significant bladder outlet obstruction (use with caution) 4
• Concomitant use of medications metabolized by CYP2D6 (may require dose adjustment) 4

Step 3: Initiate Mirabegron Therapy

• Starting dose: 25 mg once daily
• May increase to 50 mg once daily based on individual response and tolerability 4
• Extended-release tablets should be taken with water and swallowed whole
• Can be taken with or without food 4

Special Considerations

Blood Pressure Monitoring

• Mirabegron can increase blood pressure
• Periodic blood pressure monitoring is recommended, especially in hypertensive patients
• At the maximum recommended dose of 50 mg, mean increase in systolic/diastolic blood pressure is approximately 0.5-1 mmHg greater than placebo in OAB patients 4

Risk of Urinary Retention

• Use with caution in patients with clinically significant bladder outlet obstruction
• Monitor for signs and symptoms of urinary retention
• Use with caution when co-administered with antimuscarinic medications for OAB 4

Drug Interactions

• Mirabegron is a moderate CYP2D6 inhibitor
• May increase systemic exposure to CYP2D6 substrates
• Appropriate monitoring and dose adjustment may be necessary for narrow therapeutic index drugs metabolized by CYP2D6 4

Common Adverse Effects

• Hypertension
• Nasopharyngitis
• Urinary tract infection
• Headache 2, 4

Advantages Over Antimuscarinic Agents

• Incidence of dry mouth similar to placebo (3-5 times less than with antimuscarinic drugs)
• May be valuable for patients who cannot tolerate antimuscarinic side effects 2

Follow-up Recommendations

• Monitor blood pressure at baseline and periodically during treatment
• Evaluate efficacy and tolerability after 4-8 weeks of therapy
• Assess for any signs of recurrent UTI or adverse effects

UTI Prevention Strategies to Discuss

• Increased fluid intake in premenopausal women 3
• Vaginal estrogen replacement in postmenopausal women 3
• Consider immunoactive prophylaxis for recurrent UTIs 3
• Discuss cranberry products (though evidence quality is low with contradictory findings) 3

Remember that mirabegron does not have antimicrobial properties and is not a treatment for UTI itself, but rather for overactive bladder symptoms that may persist or coexist after successful treatment of the UTI.