MYRBETRIQ GRANULES
Clinical safety rating: caution
Comprehensive clinical and safety monograph for MYRBETRIQ GRANULES (MYRBETRIQ GRANULES).
Beta-3 adrenergic receptor agonist; relaxes detrusor smooth muscle during storage phase of urinary bladder filling.
| Metabolism | Primarily metabolized by CYP2D6, CYP3A4, and UGT2B7; also by alcohol dehydrogenase and aldehyde oxidase. |
| Excretion | Primarily via hepatic metabolism; renal excretion accounts for 55-60% of total clearance, with <15% unchanged in urine. Biliary/fecal elimination: 40-45% of administered dose recovered in feces, mostly as metabolites. |
| Half-life | Terminal elimination half-life: 50 hours (range 32-80 hours). Clinically, steady-state is achieved within 7 days with once-daily dosing. |
| Protein binding | Approximately 71% bound to plasma proteins, primarily to albumin and alpha-1-acid glycoprotein. |
| Volume of Distribution | Volume of distribution (Vd/F): approximately 1.2 L/kg (mean 85 L). Large Vd indicates extensive tissue distribution, consistent with beta-3 adrenergic receptor expression. |
| Bioavailability | Oral bioavailability: approximately 35% (range 29-42%) due to first-pass metabolism. Food does not affect bioavailability; granules can be taken with or without food. |
| Onset of Action | Oral: Onset of clinical effect (bladder relaxation) observed within 1-2 hours post-dose. |
| Duration of Action | Duration of action: Approximately 24 hours, supporting once-daily dosing. Clinical effects on urodynamic parameters persist over the dosing interval. |
50 mg orally once daily, with or without food. May increase to 50 mg once daily if needed; maximum 50 mg/day.
| Dosage form | FOR SUSPENSION, EXTENDED RELEASE |
| Renal impairment | eGFR 15–29 mL/min/1.73 m²: 25 mg once daily. eGFR <15 mL/min/1.73 m²: not recommended. |
| Liver impairment | Child-Pugh Class B: 25 mg once daily. Child-Pugh Class C: not recommended. |
| Pediatric use | Not approved for pediatric use; safety and efficacy not established. |
| Geriatric use | No dose adjustment required based on age alone; monitor renal function and adjust per renal criteria. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for MYRBETRIQ GRANULES (MYRBETRIQ GRANULES).
| Breastfeeding | Unknown if excreted in human milk. M/P ratio not available. Caution recommended; avoid use in nursing mothers. |
| Teratogenic Risk | Pregnancy Category C. Animal studies (rats, rabbits) show fetal toxicity at 7-28 times human exposure. No adequate human studies. First trimester: unknown risk. Second/third trimester: potential for fetal harm; use only if benefit outweighs risk. |
| Fetal Monitoring |
■ FDA Black Box Warning
None.
| Serious Effects |
["Hypersensitivity to mirabegron or any component","Uncontrolled severe hypertension (systolic ≥180 mm Hg or diastolic ≥110 mm Hg)"]
| Precautions | ["Urinary retention (especially in patients with bladder outflow obstruction)","Angioedema","Tachycardia and atrial fibrillation","Hypertension","Increased blood pressure in pediatric patients"] |
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| Monitor for uterine contractions (potential tocolytic effect). Assess fetal heart rate and growth. Monitor maternal BP, heart rate, and renal function; observe for urinary retention. |
| Fertility Effects | No human fertility effects reported. Animal studies show no impairment. |