| name | mirago-prescribing-guide |
| description | Complete bedside prescribing reference for Mirago (mirabegron, beta-3 adrenoceptor agonist) for overactive bladder — covering contraindications, safety screening, drug interactions, dose selection in special populations, titration, and administration. Use when a clinician asks how to start mirabegron, what dose to use in renal or hepatic impairment, is mirabegron safe in this patient, mirabegron drug interactions, or Mirago for OAB. |
Mirago (mirabegron) — Complete Prescribing Guide
Indian brand: Mirago | Drug class: Selective beta-3 adrenoceptor agonist
Available strengths: 25 mg, 50 mg extended-release tablets (once daily)
STEP 1 — Confirm Indication
Indicated for: Overactive bladder (OAB) in adults with:
- Urgency
- Urgency urinary incontinence
- Urinary frequency
Not established in: Pediatrics (<18 years)
Geriatrics (≥65 years): Safe to use — no dose adjustment needed
STEP 2 — Contraindications (Hard Stop)
Do NOT prescribe if ANY of these apply:
| Condition | Threshold |
|---|
| Severe uncontrolled hypertension | SBP ≥180 mmHg and/or DBP ≥110 mmHg |
| Pregnancy | Any trimester |
| Hypersensitivity to mirabegron | Any ingredient in the formulation |
STEP 3 — Safety Warnings (Proceed with Caution)
Work through each before prescribing:
Cardiovascular
- Hypertension (controlled): Check BP at baseline and periodically. Mirago raises BP ~0.5–1 mmHg in OAB patients; up to 4/3.7 mmHg in healthy volunteers at 50 mg.
- QTc prolongation risk: Mirago causes dose-dependent QTc prolongation (<5 ms at 50 mg — therapeutic dose). Use with caution if: known QT prolongation history, hypokalemia, or concurrent QTc-prolonging drugs.
- Tachyarrhythmia / ischemic heart disease: Mirago increases HR by ~1 bpm (OAB patients at 50 mg); up to 8.5 bpm in healthy female volunteers. Use caution.
Genitourinary
- Bladder outlet obstruction (BOO): Urinary retention reported post-marketing, especially with concurrent antimuscarinics. Use with caution.
Immune
- Angioedema (face, lips, tongue, larynx): Rare but life-threatening. Discontinue immediately; secure airway if upper airway involved.
Ophthalmological
- Glaucoma: Monitor IOP regularly during treatment (though 100 mg did not increase IOP in phase 1 studies).
Nursing mothers: Avoid — excreted in rodent milk; no human data.
STEP 4 — Drug Interaction Check
Run through this table for every patient:
| Co-medication | Mechanism | Action Required |
|---|
| Flecainide, propafenone (narrow TI CYP2D6 substrates) | Mirago ↑ their exposure substantially | Cap Mirago at 25 mg/day. Do not escalate. |
| Metoprolol, desipramine (CYP2D6 substrates, wider TI) | Mirago ↑ Cmax by ~79–90% | Caution; monitor for β-blocker/TCA side effects |
| Digoxin | Mirago weak P-gp inhibitor: ↑ digoxin Cmax 29%, AUC 27% | Start digoxin at lowest dose; titrate by serum levels |
| Antimuscarinics for OAB (solifenacin, oxybutynin, etc.) | Additive urinary retention risk in BOO | Caution in BOO; watch for retention |
| QTc-prolonging drugs (see list below) | Additive QTc risk | Avoid combination if patient has QT risk factors |
| Warfarin | Minor ↑ in warfarin Cmax/AUC (~4–9%); no INR effect on single dose | Monitor INR; long-term interaction not fully studied |
| Metformin, solifenacin, tamsulosin, ketoconazole, rifampicin | No clinically significant PK interaction | No dose adjustment needed |
QTc-prolonging drugs to flag:
Class IA/IC/III antiarrhythmics · Antipsychotics (haloperidol, chlorpromazine, ziprasidone) · TCAs (amitriptyline, imipramine) · Macrolides (erythromycin, clarithromycin) · Quinolones (moxifloxacin, levofloxacin) · Azole antifungals · Antimalarials (chloroquine, quinine) · Methadone · Domperidone · 5-HT3 antagonists (ondansetron) · SSRIs/SNRIs (fluoxetine, citalopram, venlafaxine)
STEP 5 — Dose Selection by Patient Profile
| Patient | Starting Dose | Maximum Dose |
|---|
| Standard adult | 25 mg OD | 50 mg OD |
| Elderly ≥65 years | 25 mg OD | 50 mg OD (no adjustment) |
| Mild renal impairment (CrCl/eGFR 30–89 mL/min) | 25 mg OD | 50 mg OD |
| Severe renal impairment (CrCl/eGFR 15–29 mL/min) | 25 mg OD | 25 mg OD — do not escalate |
| ESRD (CrCl/eGFR <15, or on dialysis) | NOT RECOMMENDED | — |
| Mild hepatic impairment (Child-Pugh A) | 25 mg OD | 50 mg OD |
| Moderate hepatic impairment (Child-Pugh B) | 25 mg OD | 25 mg OD — do not escalate |
| Severe hepatic impairment (Child-Pugh C) | NOT RECOMMENDED | — |
| With flecainide or propafenone | 25 mg OD | 25 mg OD — do not escalate |
STEP 6 — Titration and Administration
- Start: 25 mg once daily, with or without food
- Assess response: At 8 weeks (effective within 8 weeks at 25 mg)
- Escalate to 50 mg: If inadequate response and well-tolerated; once daily
- Do not exceed 50 mg/day (supra-proportional bioavailability increases above this dose)
- Administration: Swallow whole with water — do NOT crush, chew, or divide tablet
- Missed dose: Take next scheduled dose as usual — never double-dose
STEP 7 — Clinical Guardrails
- Urine dipstick protein: Mirago may cause false-positive results. Always confirm with quantitative protein assay if dipstick is positive.
- Liver enzymes: ALT/AST rose >10-fold in 0.3% of patients on 50 mg in long-term studies (subsequently normalised). Monitor if hepatic symptoms develop.
- Angioedema: Can occur after first dose or after multiple doses. If tongue, hypopharynx, or larynx involved — STOP immediately, manage airway.
- Stevens-Johnson syndrome: Rare (single case report at 100 mg). Discontinue if severe skin reaction develops.
- Do not use in pregnancy — embryo-fetal toxicity in animals (wavy rib, cardiomegaly, reduced fetal weight).
- Neoplasm signal: 1.3% at 100 mg (long-term study) vs 0.1% at 50 mg and 0.5% active control — unclear significance; not a reason to avoid at therapeutic dose (50 mg), but worth noting in long-term users.
Source: Myrbetriq (mirabegron) Canadian Product Monograph, Astellas Pharma Canada, June 2016. Submission No: 192447. Indian brand equivalent: Mirago (mirabegron).
