Mirabegron: Nursing Drug Guide, Hypertension & Urinary Retention
Beta-3 adrenergic agonist for overactive bladder: track blood pressure after every dose change, watch for urinary retention when combined with antimuscarinics or BPH, and verify extended-release tablets are never crushed.
Mirabegron (Myrbetriq) relaxes the detrusor through beta-3 receptors but can raise blood pressure and is not recommended when systolic BP is ≥180 mm Hg and/or diastolic BP is ≥110 Hg. Labeling also reports urinary retention in patients with bladder outlet obstruction and in patients taking muscarinic antagonists (including combined solifenacin therapy). Nurses must obtain baseline and follow-up BP, assess voiding after initiation or dose increases, and hold the drug for angioedema or suspected retention—especially with alpha-blocker therapy for BPH.
📋 Contents
⚡ Quick facts
💡 Key takeaway
Before every dose, check blood pressure and voiding pattern—especially after titration to 50 mg or when mirabegron is combined with an antimuscarinic or BPH therapy. Swallow extended-release tablets whole; crushing destroys the formulation and can worsen side effects.
Most common brand names
Mirabegron is marketed as Myrbetriq (extended-release tablets and granules for oral suspension in pediatric neurogenic detrusor overactivity). Multiple generic extended-release tablets are available. Myrbetriq tablets and Myrbetriq Granules are not substitutable on a milligram-per-milligram basis—verify the ordered product, indication, and weight-based pediatric dosing before administration.
Why we give it — Indications
Mirabegron treats bladder-storage symptoms without relying on antimuscarinic pathways—an important option when anticholinergic adverse effects are poorly tolerated.
| Use | Detail |
|---|---|
| Overactive bladder (adults) | Urge urinary incontinence, urgency, and urinary frequency—alone or with solifenacin 5 mg daily per labeling |
| Neurogenic detrusor overactivity (pediatrics) | Ages 3 years and older; product and weight-based dosing differ from adult tablets—follow full prescribing information |
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How it works
Mirabegron is a selective beta-3 adrenergic receptor agonist. During the storage phase of the micturition cycle, it relaxes the detrusor smooth muscle to increase bladder capacity. Unlike oxybutynin and other muscarinic antagonists, it does not depend on anticholinergic blockade—so dry mouth and constipation may be less prominent, but sympathetic effects (including increased blood pressure) remain clinically relevant.
Dosing overview
Institutional protocols and product formulations may vary. Adult OAB dosing below reflects MYRBETRIQ prescribing information.
Missed dose: Take as soon as remembered unless more than 12 hours have passed since the missed dose; if >12 hours, skip and take the next dose at the usual time.
Pharmacokinetics essentials
| Parameter | Detail | Nursing implication |
|---|---|---|
| Half-life | ~50 hours in adults; ~26–31 hours in pediatric patients (labeling) | Steady state and BP changes may lag for days after dose changes—do not judge safety from a single early BP |
| Metabolism | Multiple pathways; moderate CYP2D6 inhibitor | Review metoprolol, digoxin, and other CYP2D6 substrates at initiation |
| Renal elimination | Dose adjustment required at low eGFR | Check eGFR before starting and after acute kidney injury |
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Before you give it — Safety check
Pretreatment checks
- Blood pressure (baseline and history of hypertension)
- Voiding pattern, post-void residual if available, and symptoms of incomplete bladder emptying
- Concurrent antimuscarinics, alpha-blockers, and other bladder medications on the MAR
- Renal and hepatic function (CKD, Child-Pugh status if known)
- Allergy history and prior angioedema to mirabegron components
Contraindications
- Known hypersensitivity to mirabegron or any inactive ingredient
Important interactions
| Drug / class | Effect | Nursing action |
|---|---|---|
| CYP2D6 substrates (e.g., metoprolol, desipramine) | Increased systemic exposure when coadministered | Monitor HR/BP and clinical effect; involve pharmacy for narrow index agents (thioridazine, flecainide, propafenone per labeling) |
| Digoxin | Increased digoxin exposure when combined | Use lowest initial digoxin dose; monitor serum digoxin and toxicity signs |
| Muscarinic antagonists / BOO | Urinary retention reported | Assess voiding; consider bladder scan; hold if retention suspected |
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Administration
Route: Oral extended-release tablet (adults) or extended-release granule suspension (pediatrics per labeling).
- Swallow tablets whole with water—do not chew, divide, or crush
- Adults may take with or without food; pediatric tablet labeling specifies with food
- Give combination mirabegron + solifenacin doses at the same time once daily when prescribed together
Crushing or splitting destroys extended-release delivery and is not supported in labeling. Use liquid/granule formulations for patients who cannot swallow whole tablets.
Expected therapeutic response
- Reduced urinary frequency and urgency episodes over weeks (not immediate)
- Fewer urge incontinence episodes when OAB is the indication
- Stable blood pressure and adequate voiding without rising post-void residual
Red flags — Stop and act
Escalate urgently per facility protocol and local emergency guidance when:
- Severe uncontrolled hypertension (≥180/≥110 mm Hg) or acute hypertensive symptoms
- Unable to void, suprapubic pain, or rising post-void residual suggesting urinary retention
- Angioedema of face, lips, tongue, or larynx; difficulty breathing or swallowing
- Sustained tachycardia or palpitations with hemodynamic compromise
- Signs of digoxin toxicity when coadministered (nausea, vision changes, bradycardia)
Adverse effects
| Adverse effect | Frequency / severity | Nursing response |
|---|---|---|
| Hypertension* | 7.6% (25 mg) and 11.3% (50 mg) vs 7.5% placebo in 12-week OAB trials | Monitor BP; hold and notify if severe uncontrolled hypertension or symptomatic rise |
| Nasopharyngitis, headache, UTI | Among most common (>2% and > placebo) monotherapy reactions | Supportive care; differentiate UTI symptoms from OAB flare; obtain urinalysis if clinically indicated |
| Dry mouth, constipation, tachycardia | More prominent with mirabegron + solifenacin combination | Monitor HR; bowel and hydration support; review anticholinergic burden |
| Angioedema | Reported postmarketing; may occur after first or later doses | Stop drug; emergency airway management per protocol |
*Includes blood pressure above normal range and BP increased from baseline, predominantly in patients with baseline hypertension (labeling).
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Overdose, toxicity, and antidote
Healthy-volunteer data cited in labeling: single doses up to 400 mg caused palpitations and pulse >100 bpm; multidose 300 mg daily for 10 days increased pulse and systolic BP.
- Antidote: Not specified in the reviewed prescribing information—treatment is symptomatic and supportive
- Monitoring: Pulse rate, blood pressure, and ECG per labeling
- Contact local poison control or medical toxicology services for overdose guidance per facility protocol
Look-alike / sound-alike and error prevention
- Myrbetriq vs Myrbetriq Granules—verify product, indication, and weight; do not substitute mg-for-mg
- Mirabegron vs antimuscarinic names—confirm beta-3 agonist on MAR; do not assume “bladder medication” class is interchangeable
- Extended-release crushing—high-risk with whole-tablet-only instructions; use pharmacy alternatives for dysphagia
- No widely published LASA partner pair was identified in the reviewed prescribing information; still use tall-man lettering and independent double-check per institutional policy
Practical bedside notes
- Schedule BP checks after initiation and 4–8 week titration windows—therapeutic bladder effects may lag behind BP changes
- Ask specifically about weak stream, dribbling, and abdominal fullness—retention can be silent in older adults
- Perform medication reconciliation for OTC cold meds and duplicate bladder agents at admission
- Teach patients not to double doses after a missed tablet; follow the 12-hour rule in labeling
High-risk populations
| Population | Considerations |
|---|---|
| Hypertension / cardiovascular disease | Periodic BP monitoring required; not recommended with severe uncontrolled hypertension |
| Bladder outlet obstruction / BPH | Use caution; monitor for retention even though one BOO safety study did not show increased retention |
| Renal impairment | Dose limits per eGFR; not recommended if eGFR <15 or dialysis |
| Pregnancy | Animal data show fetal toxicity at high multiples of human exposure; human data inadequate—use only if benefit justifies risk per labeling |
| Lactation | No human milk data; mirabegron present in rat milk—balance breastfeeding benefits with potential infant exposure per labeling |
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Monitoring and documentation
Monitor
- Blood pressure periodically—especially in treated hypertension
- Heart rate (tachycardia with combination therapy)
- Voiding pattern, post-void residual, or bladder scan when retention suspected
- Serum digoxin when starting or changing dose with concurrent digoxin
- Renal/hepatic labs when clinically indicated for dose selection
Document
- Baseline and follow-up BP with mirabegron dose changes
- Voiding assessments and retention interventions
- Patient teaching on swallowing whole tablets and missed-dose rules
- Pharmacy consult for CYP2D6 interactions and renal/hepatic adjustments
Patient teaching
- Take once daily at the same time; swallow the tablet whole with water
- Report inability to urinate, suprapubic discomfort, severe headache, or facial swelling immediately
- Home BP monitoring may be recommended when hypertension is present—follow prescriber plan
- Do not stop abruptly without prescriber guidance; benefit may take several weeks
- Seek emergency care for angioedema or breathing difficulty; contact local poison control for suspected overdose per regional guidance
The Hold Rule
Do not give and contact the prescriber/pharmacist when:
- Known hypersensitivity to mirabegron or excipients
- Severe uncontrolled hypertension (≥180 systolic and/or ≥110 diastolic) per labeling
- Suspected urinary retention or inability to void
- eGFR <15 mL/min/1.73 m² or dialysis requirement (not recommended)
- Child-Pugh Class C hepatic impairment (not recommended)
- Angioedema or anaphylaxis symptoms
Hold parameters may vary by institutional protocol. Follow prescriber orders, pharmacy guidance, and facility policy.
Clinical practice integration and workflow
Mirabegron safety is a BP-and-voiding story—pair every bladder symptom review with cardiovascular and retention checks.
1. Check-before-you-give protocol
- Correct product (tablet vs granules) and dose for eGFR/hepatic status
- BP within prescriber parameters—not severe uncontrolled hypertension
- Voiding adequate since last dose; no acute retention signs
- Tablet intact—never crush extended-release mirabegron
2. High-alert and safety badge
Not a traditional high-alert medicationTreat as high-risk for BP elevation, urinary retention, and formulation errors (crushing, product substitution).
3. Clinical workflow: hold and question rules
- Hold for retention or angioedema; notify prescriber and pharmacy
- Question orders exceeding renal/hepatic maximums
- Request digoxin level review when mirabegron is added to digoxin therapy
4. Critical teach-back questions
- “How do you take this tablet?” Swallowed whole once daily—not chewed or crushed
- “When should you call the clinic?” Unable to urinate, severe headache, facial swelling, or BP above prescriber targets
5. Care coordination
Pharmacist: Renal/hepatic dose verification, CYP2D6 interaction review, digoxin level planning
Prescriber / urology: Retention management, combination therapy decisions, and titration after 4–8 weeks
🧠 Quick mental checklist
- BP today acceptable for mirabegron?
- Voiding OK—no retention cues?
- Whole tablet—no crushing?
- Any new digoxin or metoprolol interaction check?
- eGFR/hepatic status supports this dose?
Mirabegron NCLEX practice questions
Rehearse NCLEX-style clinical judgment practice for mirabegron blood pressure and urinary retention safety using a tabbed outpatient case (MAR, labs, vitals, nursing notes), then priority action, cue recognition (SATA), BP/voiding trend interpretation, matrix urgency sorting, digoxin interaction judgment, and documentation cloze—recognise cues → analyse → prioritise → act → evaluate outcomes.
Select a tab to view MAR, labs, vitals, and nursing note details for this case.
- Mirabegron (Myrbetriq) 25 mg PO daily — day 10; due 0800
- Solifenacin 5 mg PO daily — same schedule (combination OAB therapy)
- Tamsulosin 0.4 mg PO daily — BPH
- Lisinopril 10 mg PO daily — hypertension
- Digoxin 0.125 mg PO daily — atrial fibrillation rate control
- eGFR 58 mL/min/1.73 m² (stable CKD stage 3a)
- Serum digoxin 0.8 ng/mL (therapeutic range per facility)
- AST/ALT within normal limits
- Urinalysis yesterday: negative nitrites; no culture ordered
- Admission (pre-mirabegron): BP 138/82 mm Hg; HR 78
- Day 7: BP 148/88 mm Hg; HR 82
- Today 0745: BP 168/96 mm Hg; HR 94; temp 36.8 °C
- Bladder scan (yesterday): post-void residual 120 mL
- 72-year-old with OAB and BPH; mirabegron started on last admission
- Reports frontal headache this morning and “weak stream” × 2 days
- Last void 6 h ago, 80 mL; denies suprapubic pain
- States he did not chew tablet; daughter crushes other meds at home—education reinforced
Answer key & rationale
Frequently asked questions
Why does mirabegron require blood pressure monitoring?
MYRBETRIQ labeling states mirabegron can increase blood pressure. Periodic BP monitoring is recommended, especially in hypertensive patients. The drug is not recommended when systolic BP is at least 180 mm Hg and/or diastolic BP is at least 110 mm Hg.
When should a nurse hold mirabegron?
Hold for hypersensitivity, severe uncontrolled hypertension per labeling, suspected urinary retention, eGFR below 15 mL/min/1.73 m² or dialysis, Child-Pugh Class C hepatic impairment, angioedema, or orders to crush/split extended-release tablets.
Can mirabegron be given with solifenacin?
Yes when prescribed for OAB, but urinary retention has been reported with bladder outlet obstruction and muscarinic antagonists. Monitor voiding and post-void residual closely.
How does mirabegron affect digoxin?
When initiating mirabegron with digoxin, labeling directs using the lowest digoxin dose and monitoring serum digoxin concentrations for titration.
What should patients do if they miss a dose?
Take the missed dose as soon as remembered unless more than 12 hours have passed; then skip and resume the next dose at the usual time.
Is there an antidote for mirabegron overdose?
No specific antidote is listed. Treatment is symptomatic and supportive with pulse, BP, and ECG monitoring. Contact local poison control or toxicology services per facility protocol.
References
- U.S. National Library of Medicine. MYRBETRIQ (mirabegron) — Full prescribing information. DailyMed.https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=ba9e9e15-e666-4c56-9271-2e24739cfa2d
- U.S. Food and Drug Administration. MedWatch: The FDA Safety Information and Adverse Event Reporting Program.https://www.accessdata.fda.gov/scripts/medwatch/
- National Library of Medicine. Drugs and Lactation Database (LactMed) — About and peer review. NCBI Bookshelf.https://www.ncbi.nlm.nih.gov/books/NBK501922/
Review and transparency
This medication guide is written and reviewed using NurseOnShift editorial and clinical review standards.
Educational use only. This content does not replace clinical judgment, prescriber orders, pharmacist guidance, product labeling, or institutional protocols.