MYRBETRIQ
Clinical safety rating: caution
Comprehensive clinical and safety monograph for MYRBETRIQ (MYRBETRIQ).
Selective beta-3 adrenergic receptor agonist; relaxes detrusor smooth muscle during storage phase of urinary bladder filling, increasing bladder capacity.
| Metabolism | Primarily metabolized by CYP2D6, CYP3A4, and UGT; additional contributions from CYP2C9, CYP2C19, and CYP2E1. |
| Excretion | Primarily renal (55% unchanged) and fecal (43%, mainly as metabolites), with <1% biliary. |
| Half-life | Terminal elimination half-life is approximately 50 hours (range 32–80 h) in healthy adults, allowing 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 is about 50 L (0.7 L/kg), indicating extensive tissue distribution. |
| Bioavailability | Absolute oral bioavailability is approximately 29% (range 17–44%), with food decreasing peak concentration but not AUC. |
| Onset of Action | Onset of clinical effect on detrusor relaxation occurs within 3–8 hours after oral administration. |
| Duration of Action | Duration of action is approximately 24 hours, supporting once-daily dosing for overactive bladder symptoms. |
25 mg orally once daily, with or without food, may increase to 50 mg once daily after 4-8 weeks if needed.
| Dosage form | TABLET, EXTENDED RELEASE |
| Renal impairment | eGFR 15-29 mL/min: 25 mg once daily; eGFR <15 mL/min or dialysis: not recommended. |
| Liver impairment | Child-Pugh Class A: no adjustment; Child-Pugh Class B: 25 mg once daily; Child-Pugh Class C: not recommended. |
| Pediatric use | Not approved for use in pediatric patients. |
| Geriatric use | No specific dose adjustment required; monitor for adverse effects due to potential age-related renal impairment. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for MYRBETRIQ (MYRBETRIQ).
| Breastfeeding | It is not known whether mirabegron is excreted in human milk. No M/P ratio is available. Caution should be exercised when administered to a nursing woman, considering the importance of the drug to the mother. |
| Teratogenic Risk | Pregnancy Category C. There are no adequate and well-controlled studies in pregnant women. In animal studies, mirabegron caused reduced fetal weights and increased incidences of skeletal variations at exposures 6-7 times the maximum recommended human dose. Risk cannot be ruled out; use only if potential benefit justifies potential risk to the fetus. |
■ FDA Black Box Warning
None
| Serious Effects |
Hypersensitivity to mirabegron or any component; severe uncontrolled hypertension (systolic ≥180 mm Hg or diastolic ≥110 mm Hg).
| Precautions | May increase blood pressure and heart rate; monitor for hypertensive crisis in uncontrolled hypertension, tachycardia, atrial fibrillation. Use with caution in patients with bladder outlet obstruction, urinary retention, and gastrointestinal obstructive disorders. May cause angioedema. Dose adjustment recommended for severe renal impairment (eGFR 15-29 mL/min/1.73 m²) or moderate hepatic impairment (Child-Pugh Class B). |
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| Fetal Monitoring |
| Monitor maternal blood pressure and heart rate due to mirabegron's potential to increase blood pressure and heart rate. Fetal monitoring should include standard antenatal assessments; consider ultrasound for fetal growth if prolonged use is required. |
| Fertility Effects | Based on animal studies, mirabegron may impair fertility in females and males. In female rats, decreased fertility and increased preimplantation loss were observed at exposures 7 times the MRHD. In male rats, impaired spermatogenesis and reduced fertility were noted at high doses. Relevance to human fertility is unknown. |