mirabegron

General

Pronunciation:
mye-ra-beg-ron

Trade Name(s)

• Myrbetriq

Ther. Class.
urinary tract antispasmodics

Pharm. Class.
beta-adrenergic agonists

Indications

Treatment of symptoms of overactive bladder (OAB) including urge urinary incontinence, urgency, and frequency (either alone or with solifenacin).

Action

• Acts as a selective beta-3 adrenergic agonist.
• Increases bladder capacity by relaxing detusor smooth muscle during storage phase of bladder fill-void cycle.

Therapeutic Effect(s):

Decreased symptoms of OAB.

Pharmacokinetics

Absorption: 29–35% absorbed following oral administration.

Distribution: Widely distributed.

Metabolism and Excretion: Extensively metabolized, 6% excreted unchanged in urine (25 mg dose), remainder excreted in urine and feces as metabolites.

Half-life: 50 hr.

TIME/ACTION PROFILE (effects on bladder)

Contraindication/Precautions

Contraindicated in:

• Hypersensitivity;
• Severe uncontrolled hypertension;
• End-stage renal disease or severe hepatic impairment (Child-Pugh Class C);
• Lactation: Probably enters breast milk and may cause adverse reactions in infant.

Use Cautiously in:

• Hypertension;
• Bladder outlet obstruction/concurrent antimuscarics (↑ risk of urinary retention);
• Concurrent use of antimuscarinics used to treat OAB;
• OB:  Use only if potential maternal benefit outweighs risk to fetus;
• Pedi:  Safety and effectiveness not established.

Adverse Reactions/Side Effects

CNS: dizziness, headache

CV: ↑ BP, tachycardia

EENT: nasopharyngitis

GI: constipation, diarrhea, nausea

GU: urinary tract infection

Misc: ANGIOEDEMA

* CAPITALS indicate life-threatening.
Underline indicate most frequent.

Interactions

Drug-Drug

• Acts as a moderate inhibitor of the CYP2D6 enzyme system.
• May ↑ levels and risk of adverse reactions of  drugs metabolized by the CYP2D6 enzyme system  including desipramine, flecainide, metoprolol, propafenone, and  thioridazine.
• May ↑ levels and risk of toxicity with  digoxin ; use lowest effective level of digoxin/monitor serum levels).

Route/Dosage

PO (Adults): 25 mg once daily; may be ↑ to 50 mg once daily based on need/tolerance after 8 wk.

Renal Impairment 
PO (Adults):  CCr 15–20 mL/min– Should not exceed 25 mg/day.Hepatic Impairment 
PO (Adults):  Moderate hepatic impairment (Child-Pugh Class B)– Should not exceed 25 mg/day.

Availability

Extended-release tablets: 25 mg, 50 mg

Assessment

• Assess patient for urinary urgency, frequency, and urge incontinence periodically during therapy.
• Monitor BP prior to starting and periodically during therapy; may cause ↑ BP.
• Monitor for signs and symptoms of angioedema (swelling of face, lips, tongue and/or larynx). Discontinue mirabegron and treat symptomatically.

Potential Diagnoses

• Impaired urinary elimination (Indications) 
• Urinary retention (Indications) 

Implementation

• PO Administer without regard to food.
  • Swallow tablets whole with water; do not break, crush, or chew.

Patient/Family Teaching

• Instruct patient to take mirabegron as directed. If a dose is missed, omit dose and begin taking next day; do not take 2 doses on the same day. Advise patient to read  Patient Information sheet prior to starting and with each Rx refill in case of changes.
• Inform patient that mirabegron may cause an increase in BP. Advise patient to have BP checked periodically during therapy.
• May cause dizziness. Caution patient to avoid driving or other activities requiring alertness until response to medication is known.
• Advise patient to notify health care professional if difficulty emptying bladder occurs.
• Advise patient to notify health care professional of all Rx or OTC medications, vitamins, or herbal products being taken and to consult with health care professional before taking other medications.
• Advise female patients to notify health care professional if pregnancy is planned or suspected or if breast feeding.

Evaluation/Desired Outcomes

Decreased urinary frequency, urgency, and urge incontinence.