Methylergometrine Tablets

Mechanism

Methylergometrine acts as a 5-HT2B receptor agonist, D1 receptor antagonist, and partial alpha-adrenergic agonist. This combination produces sustained uterine contractions, reducing bleeding after childbirth. Unlike oxytocin, which causes rhythmic contractions, methylergometrine induces tonic contractions.

Pharmacokinetics

• Onset: IM – immediate; IV – within minutes
• Duration: IM/Oral – ~3 hours; IV – ~45 minutes
• Metabolism: Hepatic
• Excretion: Bile and feces

Side Effects

• Headache, dizziness, nausea, vomiting
• Hypertension due to vasoconstriction
• Chest pain or angina (risk of coronary spasm)
• Difficulty breathing

Contraindication

• Hypertension, preeclampsia, eclampsia
• Coronary artery disease or peripheral vascular disease
• Pregnancy (except postpartum use)
• Known allergy to ergot derivatives

Interaction

• Vasoconstrictors & sympathomimetics: May cause severe hypertension.
• Macrolide antibiotics (e.g., erythromycin, clarithromycin): Increase risk of ergot toxicity due to CYP3A4 inhibition.
• Protease inhibitors (HIV therapy): Can elevate methylergometrine levels, leading to vasospasm.
• Other ergot alkaloids: Additive toxicity and vasospasm risk.

Warning and Precautions

• Monitor blood pressure closely; risk of severe hypertension.
• Use with caution in patients with cardiovascular disease.
• Not recommended during breastfeeding unless benefits outweigh risks.
• Should only be used postpartum; contraindicated during pregnancy.
• Discontinue immediately if chest pain, severe headache, or signs of vasospasm occur.

Dosage

As directed by the Physician.