MIRABEGRON
Clinical safety rating: safe
Animal studies have demonstrated safety
Beta-3 adrenergic receptor agonist; relaxes detrusor smooth muscle during storage phase of urinary bladder filling.
| Metabolism | Primarily metabolized via glucuronidation (UGT2B7); also undergoes oxidation via CYP3A4, CYP2D6, and CYP2C9; minor role of CYP2C19 and CYP2C8. |
| Excretion | Approximately 55% of the dose is excreted unchanged in urine, with 45% metabolized; fecal excretion accounts for about 22% (mainly as metabolites). |
| Half-life | Terminal elimination half-life is approximately 50 hours, allowing once-daily dosing; steady state reached after 7 days. |
| Protein binding | 71% bound to serum albumin and alpha-1-acid glycoprotein. |
| Volume of Distribution | Volume of distribution is 1670 L (approx. 23.9 L/kg for a 70 kg adult), indicating extensive tissue distribution. |
| Bioavailability | Oral bioavailability is 29% (range 15-41%) due to first-pass metabolism. |
| Onset of Action | Oral: 3-7 days for initial therapeutic effect; maximal effect at week 8. |
| Duration of Action | Duration of action is 24 hours due to once-daily dosing; sustained effect over 24 hours confirmed in clinical trials. |
50 mg orally once daily, with or without food.
| Dosage form | TABLET, EXTENDED RELEASE |
| Renal impairment | GFR 30-89 mL/min: No adjustment. GFR 15-29 mL/min: Not recommended. GFR <15 mL/min or dialysis: Not recommended. |
| Liver impairment | Child-Pugh A: No adjustment. Child-Pugh B: Not recommended. Child-Pugh C: Not recommended. |
| Pediatric use | Not approved for pediatric use; safety and efficacy not established. |
| Geriatric use | No specific dose adjustment required; monitor for anticholinergic effects (dry mouth, constipation) and blood pressure. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Strong CYP2D6 inhibitors may increase levels Can increase blood pressure and cause urinary retention.
| Breastfeeding | Mirabegron is excreted in rat milk, but human data are lacking. The manufacturer recommends caution in breastfeeding women. No milk-to-plasma (M/P) ratio is available for humans. Consider the developmental and health benefits of breastfeeding along with the mother's clinical need for mirabegron. |
| Teratogenic Risk | Mirabegron is classified as FDA Pregnancy Category C. In animal studies, no teratogenic effects were observed at exposures up to 14 times the maximum recommended human dose (MRHD). However, delayed ossification and reduced fetal weights occurred at maternally toxic doses. There are no adequate and well-controlled studies in pregnant women. Risk cannot be ruled out, and use only if potential benefit justifies potential risk to the fetus. |
■ FDA Black Box Warning
None.
| Common Effects | Hypertension |
| Serious Effects |
Hypersensitivity to mirabegron or any component of the formulation; severe uncontrolled hypertension (systolic ≥180 mmHg or diastolic ≥110 mmHg).
| Precautions | ["Urinary retention (especially in patients with bladder outlet obstruction or taking antimuscarinics)","Angioedema (discontinue if occurs)","Hypertension (monitor blood pressure)","Patients with severe uncontrolled hypertension (systolic ≥180 mmHg or diastolic ≥110 mmHg) should not be initiated on mirabegron"] |
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| Fetal Monitoring | No specific maternal-fetal monitoring is required beyond standard prenatal care. Monitor maternal blood pressure and heart rate due to possible increases; assess for hypertensive effects during pregnancy. |
| Fertility Effects | In animal studies, mirabegron had no effect on male or female fertility at exposures up to 14 times the MRHD. There are no human data on fertility effects. No specific guidance on reproductive impact. |