Mirabegron for overactive bladder

NICE state that (1)

• "..Mirabegron is recommended as an option for treating the symptoms of overactive bladder only for people in whom antimuscarinic drugs are contraindicated or clinically ineffective, or have unacceptable side effects.."

Mirabegron:

• has a marketing authorisation in the UK for the 'symptomatic treatment of urgency, increased micturition frequency and/or urgency incontinence as may occur in patients with overactive bladder (OAB)'
• is a beta-3-adrenoceptor agonist
  • activates beta-3-adrenoceptors causing the bladder to relax, which helps it to fill and also to store urine
  • animal studies have shown that beta-3 receptor agonists exhibit a dose-dependent detrusor relaxation (mediated via up-regulation of cyclic-adenosine) during the storage phase of micturition (2)
    • this way, mirabegron can aid in the symptomatic relief of OAB and symptoms of urge urinary incontinence, urgency, and urinary frequency
• is administered orally
• summary of product characteristics lists the following possible adverse reactions for mirabegron:
  • urinary tract infection,
  • tachycardia,
  • vaginal infection,
  • cystitis, palpitation,
  • atrial fibrillation,
  • dyspepsia,
  • gastritis,
  • urticaria,
  • rash,
  • rash macular,
  • rash papular,
  • pruritus,
  • joint swelling,
  • vulvovaginal pruritis,
  • increased blood pressure,
  • increased gamma-glutamyl transpeptidase,
  • increased aspartate aminotransferase,
  • increased alanine aminotransferase,
  • eyelid oedema,
  • lip oedema,
  • leukocytoclastic vasculitis and purpura (rash)
  • for full details of adverse reactions and contraindications, see the summary of product characteristics

Absorption of mirabegron

• mirabegron reaches maximum plasma concentrations (Cmax) at approximately 3.5 hours (2)
  • steady-state concentrations are achieved within seven days. In adults, there are no clinically significant differences in mirabegron pharmacokinetics when administered with or without food

Excretion of mirabegron

• mean elimination half-life (t1/2) of mirabegron is approximately 50 hours in adult patients and 26 to 31 hours in pediatric patients(mirabegron granules) (2)
  • renal elimination of mirabegron is primarily through active tubular secretion and glomerular filtration
  • about 55% is excreted in the urine, 34% in the feces, and ~25% in the urine(unchanged)

Mirabegron is contraindicated in patients with severe uncontrolled hypertension; advice about regular monitoring is being introduced because of cases of severe hypertension (3):

• Mirabegron is contraindicated in patients with severe uncontrolled hypertension (systolic blood pressure =180 mm Hg or diastolic blood pressure =110 mm Hg, or both)
• blood pressure should be measured before starting treatment and monitored regularly during treatment, especially in patients with hypertension

Reference:

• 1) NICE (June 2013). Mirabegron for treating symptoms of overactive bladder
• 2) Dawood O, El-Zawahry A. Mirabegron. [Updated 2023 Aug 28]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2026 Jan-.
• 3) Drug Safety Update (October 14th 2015). Mirabegron (Betmiga): risk of severe hypertension and associated cerebrovascular and cardiac events