What is the dosage and administration of Myomectin (methylergonovine) for postpartum hemorrhage?

Methylergonovine (Myomectin) Dosage and Administration for Postpartum Hemorrhage

Methylergonovine is administered as 0.2 mg intramuscularly immediately after delivery of the neonate when used in combination with oxytocin for prevention of postpartum hemorrhage, or as a second-line agent for refractory uterine atony. 1

Dosing Regimens

Prophylactic Use (Prevention)

• 0.2 mg intramuscularly given immediately after delivery of the neonate, combined with intravenous oxytocin 10 IU 1
• This combination regimen is one of several evidence-based options for preventing postpartum hemorrhage during the third stage of labor 1

Second-Line Treatment (Refractory Uterine Atony)

• 0.2 mg intramuscularly as a single dose when uterine atony persists despite first-line oxytocin therapy 2
• Methylergonovine demonstrates equivalent efficacy to carboprost for refractory uterine atony, with mean uterine tone scores of 7.3±1.7 at 10 minutes post-administration 2
• When used as second-line therapy at cesarean delivery, methylergonovine is associated with reduced hemorrhage-related morbidity compared to carboprost (relative risk 0.59,95% CI 0.38-0.83) 3

Clinical Context and Mechanism

Role in Postpartum Hemorrhage Management

• Methylergonovine acts as a vasoconstrictive uterotonic agent that enhances sustained myometrial contractions 4
• Combined therapy with oxytocin plus second-line agents like methylergonovine provides additive or synergistic effects superior to oxytocin alone for preventing postpartum hemorrhage 4
• Approximately 30% of patients receiving methylergonovine for refractory atony require additional second-line uterotonics 2

Active Management of Third Stage

• Uterotonics like methylergonovine enhance uterine contraction and promote placental separation, which is the primary physiologic mechanism to control bleeding from the placental bed 5
• Active management with uterotonics minimizes trauma and reduces bleeding risk, particularly important in patients receiving anticoagulants 5

Critical Contraindications and Safety Concerns

Absolute Contraindications

• Cardiac disease and hypertension: Methylergonovine causes vasoconstriction and is contraindicated in cardiac patients 6
• The European Heart Journal specifically recommends avoiding methylergonovine in cardiac patients due to risks of vasoconstriction and hypertension 6

Serious Adverse Events

• Coronary vasospasm: Intramuscular methylergonovine can cause coronary vasospasm leading to myocardial ischemia, even in patients without known coronary disease 7
• Case reports document ST-segment changes, troponin elevation to 1509 ng/L, decreased left ventricular ejection fraction, and wall motion abnormalities following intramuscular administration 7
• Prompt recognition and sublingual nitroglycerin administration can prevent severe complications including arrhythmias, heart block, or cardiac arrest 7

Common Pitfalls to Avoid

• Do not use in hypertensive or cardiac patients: Consider carbetocin or other alternatives that provide better hemodynamic stability 6
• Monitor for chest pain post-administration: Even intramuscular routes can cause life-threatening coronary vasospasm 7
• Do not rely on methylergonovine alone: Combined therapy is superior to single-agent oxytocin for postpartum hemorrhage prevention 4
• Recognize when additional intervention is needed: Approximately one-third of patients require additional uterotonics despite methylergonovine administration 2