mirabegron

see also:

• sympathomimetics
• overactive bladders, urgency and urge incontinence

• mirabegron is a beta-3 receptor agonist agent which is primarily used in the Rx of overactive bladders, urgency and urge incontinence
• the bladder wall muscle during the storage phase of bladder filling is mainly relaxed via beta 3 adrenergic stimulation, while the void phase is primarily via muscle contraction due to muscarinic M3 receptor stimulation
• introduced into the Australian PBS in 2013
• only recommended when antimuscarinic agents are C/I, ineffective or not tolerated

• 25-50mg daily sustained released tablet
• steady state concentrations are achieved within 7 days of once daily dosing with mirabegron and plasma levels are approximately double that seen after a single dose
• Vd at steady state 1670 L
• terminal elimination half life is 50hrs (25% renal)

• uncontrolled hypertension (systolic > 180mmHg or diastolic > 110mmHg)
• hypersensitivity to mirabegron or its ingredients - angioedema has been reported
• prolonged QTc
• high urinary retention risk esp. avoid combination with antimuscarinics if risk is high
• severe hepatic disease
• severe renal disease or dialysis
• children
• pregnancy - cat B3
• lactation as it is expressed in breast milk
• care with some medications as it does have some drug interactions such as digoxin, flecainide, tricyclic antidepressants - see product information

• most are mild effects and only 4% cease medication due to adverse reactions
• mild increase in HR and BP (usually < 5mmHG)
• nasopharyngitis, UTI, headaches occur in 3%
• constipation, diarrhoea or tachycardia occur in 1-2%
• atrial fibrillation in 1% - cease Rx
• angioedema