METHERGINE
Clinical safety rating: caution
Comprehensive clinical and safety monograph for METHERGINE (METHERGINE).
Methylergonovine is an ergot alkaloid that acts as a partial agonist at α-adrenergic receptors in the uterine smooth muscle, causing sustained contractions. It also exhibits serotonergic (5-HT2) and dopaminergic activity.
| Metabolism | Primarily hepatic via CYP3A4 with significant first-pass metabolism; active metabolite is methylergonovine itself; excreted mainly in bile and urine. |
| Excretion | Primarily hepatic metabolism; less than 1% excreted unchanged in urine. Biliary/fecal excretion accounts for ~80% of metabolites. |
| Half-life | Terminal elimination half-life is approximately 2–3 hours in healthy adults; prolonged in hepatic impairment. |
| Protein binding | Approximately 93% bound, primarily to albumin and alpha-1-acid glycoprotein. |
| Volume of Distribution | 0.6 L/kg (range 0.3–0.8 L/kg), indicating moderate distribution into tissues. |
| Bioavailability | Oral bioavailability is approximately 10–20% due to extensive first-pass metabolism. Intramuscular administration provides 100% bioavailability. |
| Onset of Action | Intravenous: within 30–60 seconds. Intramuscular: within 2–5 minutes. Oral: within 5–10 minutes. |
| Duration of Action | Intravenous: ~45 minutes. Intramuscular: 2–4 hours. Oral: 3–6 hours. Note: prolonged effect may occur in patients with hepatic dysfunction. |
0.2 mg intramuscularly or intravenously after delivery of placenta and every 2-4 hours as needed, up to a maximum of 5 doses.
| Dosage form | INJECTABLE |
| Renal impairment | No specific dose adjustment recommended; use with caution in renal impairment due to risk of hypertension. |
| Liver impairment | Contraindicated in severe hepatic impairment (Child-Pugh class C). For Child-Pugh class A or B, use with caution and monitor for signs of toxicity. |
| Pediatric use | Not recommended for pediatric use; safety and efficacy in children have not been established. |
| Geriatric use | Use with caution in elderly patients due to increased sensitivity to vasoconstrictive effects and higher risk of hypertension and myocardial ischemia. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for METHERGINE (METHERGINE).
| Breastfeeding | Methylergonovine is excreted into breast milk in small amounts; the milk-to-plasma ratio is approximately 1.0. Adverse effects in nursing infants are rare but may include diarrhea, vomiting, and hypertension. It is generally considered compatible with breastfeeding when used short-term for postpartum hemorrhage. Avoid prolonged use. |
| Teratogenic Risk | Methergine (methylergonovine) is contraindicated in pregnancy due to its oxytocic properties and risk of uterine hyperstimulation, fetal distress, and abortion. First trimester: potential teratogenic effects not well studied; avoid use. Second and third trimesters: can cause abruptio placentae, premature labor, and fetal anoxia. It is FDA Pregnancy Category X. |
■ FDA Black Box Warning
Not for use during pregnancy (except during delivery) due to risk of uterine tetany and fetal hypoxia. Contraindicated in patients with hypertension, preeclampsia, or eclampsia due to risk of severe hypertension and stroke.
| Common Effects | High blood pressure Headache Seizure |
| Serious Effects |
["Hypersensitivity to ergot alkaloids","Pregnancy (for antepartum use)","Hypertension, preeclampsia, or eclampsia","Peripheral vascular disease","Coronary artery disease","Severe hepatic or renal impairment","Sepsis"]
| Precautions | ["Risk of severe hypertension, especially in patients with preeclampsia, eclampsia, or hypertension.","Use with caution in patients with sepsis, hepatic or renal impairment, or coronary artery disease.","May cause ergotism with prolonged use or high doses (symptoms: vasospasm, ischemia).","Monitor blood pressure and uterine response during administration."] |
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| Fetal Monitoring | Monitor maternal blood pressure, uterine tone, and bleeding. Observe for signs of uterine hyperstimulation or tetany. In neonates, monitor for jitteriness, vomiting, or diarrhea if exposed via breast milk. |
| Fertility Effects | No specific data on fertility effects. As an ergot alkaloid, it may interfere with implantation if used in early pregnancy, but it is not indicated for use in conception cycles. |