mirabegron

(mye-ra-beg-ron) mirabegron,

Myrbetriq

(trade name)

Classification

Therapeutic: urinary tract antispasmodics
Pharmacologic: beta adrenergic agonists
Pregnancy Category: C

Indications

Treatment of symptoms of overactive bladder (OAB) including urge urinary incontinence, urgency, and frequency.

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 effects

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)

ROUTE	ONSET	PEAK	DURATION
PO	unknown	3.5 hr†	24 hr

†Blood level.

Contraindications/Precautions

Contraindicated in: Severe uncontrolled hypertension; Lactation: Probably enters breast milk and may cause adverse reactions in infant;End-stage renal disease or severe hepatic impairment (Child-Pugh Class C).Use Cautiously in: Hypertension;Bladder outlet obstruction/concurrent antimuscarics (↑ risk of urinary retention);Concurrent use of antimuscarinics used to treat OAB; Obstetric: Use only potential maternal benefit outwieghs risk to patient/fetus; Pediatric: Safe and effective use in children has not been established.

Adverse Reactions/Side Effects

Central nervous system

dizziness
headache

Ear, Eye, Nose, Throat

nasopharyngitis

Cardiovascular

↑ BP
tachycardia

Gastrointestinal

constipation
diarrhea
nausea

Genitourinary

urinary tract infection

Interactions

Drug-Drug interaction

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

Route/Dosage

Oral (Adults) 25 mg once daily initially is usually effective within 8 wk, may be ↑ to 50 mg once daily based on need/tolerance.

Renal Impairment

Oral (Adults) Severe renal impairment (CCr15–20 mL/min)—dose should not exceed 25 mg/day.

Hepatic Impairment

Oral (Adults) Moderate hepatic impairment (Child-Pugh Class B)—dose should not exceed 25 mg/day.

Availability

Extended-release tablets: 25 mg, 50 mg

Nursing implications

Nursing 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.

Potential Nursing Diagnoses

Impaired urinary elimination (Indications)
Urinary retention (Indications)

Implementation

Oral: 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.