What is the treatment for a non-contracting uterus after delivery with Methergine (methylergonovine)?

Methylergonovine (Methergine) for Non-Contracting Uterus After Delivery

Methylergonovine is contraindicated for treatment of uterine atony after delivery due to the significant risk (>10%) of vasoconstriction and hypertension. 1

Mechanism of Action and Pharmacology

• Methylergonovine acts directly on uterine smooth muscle, increasing tone, rate, and amplitude of contractions, producing a rapid and sustained tetanic uterotonic effect 2
• Onset of action is immediate after IV administration, 2-5 minutes after IM administration, and 5-10 minutes after oral administration 2
• The drug is rapidly distributed from plasma to peripheral tissues within 2-3 minutes after IV injection 2

Contraindications

• Methylergonovine is specifically contraindicated for postpartum hemorrhage management due to the risk of vasoconstriction and hypertension 1
• Should not be used in patients with cardiovascular disease, hypertension, or pre-eclampsia 2
• Should not be coadministered with potent CYP3A4 inhibitors (macrolide antibiotics, protease inhibitors, azole antifungals) due to risk of vasospasm leading to cerebral ischemia and/or extremity ischemia 2, 3

Recommended First-Line Treatment for Uterine Atony

• A slow IV infusion of oxytocin (<2 U/min) is the recommended first-line treatment to prevent maternal hemorrhage after placental delivery 1
• Oxytocin administration at this rate avoids systemic hypotension while promoting uterine contraction 1

Alternative Second-Line Treatments

• Prostaglandin F analogues are useful for treating postpartum hemorrhage unless an increase in pulmonary artery pressure is undesirable 1
• Tranexamic acid should be considered as part of standard treatment for postpartum hemorrhage, administered within 3 hours of birth at a fixed dose of 1g IV over 10 minutes 1
• If bleeding continues after 30 minutes or restarts within 24 hours, a second dose of 1g tranexamic acid IV can be administered 1

Comparative Efficacy of Uterotonics

• Methylergonovine has been associated with reduced risk of hemorrhage-related morbidity compared to carboprost during cesarean delivery, suggesting it may be a more effective second-line uterotonic when appropriately indicated 4
• Combined therapy using oxytocin with second-line uterotonics has shown additive or synergistic effects with greater risk reduction for postpartum hemorrhage prevention compared to oxytocin alone 5

Management Approach for Uterine Atony

1. First-line treatment: Slow IV infusion of oxytocin (<2 U/min) after placental delivery 1
2. For refractory cases: Consider prostaglandin F analogues unless contraindicated 1
3. Add tranexamic acid (1g IV over 10 minutes) within 3 hours of birth 1
4. Consider additional interventions if bleeding persists:
   • Non-surgical interventions: bimanual compression, intrauterine balloon tamponade, non-pneumatic antishock garment, external aortic compression 1
   • Surgical interventions: brace sutures, arterial ligation, or hysterectomy 1

Important Considerations

• Postpartum hemorrhage is defined as blood loss >500mL after vaginal delivery or >1000mL after cesarean section during the first 24 hours post-delivery 6
• Uterine atony is the most prevalent cause of postpartum hemorrhage 6, 5
• Hemodynamic monitoring should be continued for at least 24 hours after delivery, particularly in women with structural heart disease 1
• There is wide interhospital variation in the use of second-line uterotonics that is not explained by patient-level or hospital-level characteristics 7

Caution

• Despite methylergonovine's effectiveness as a uterotonic agent, its cardiovascular side effects make it unsuitable for first-line treatment of uterine atony 1
• The drug should be avoided in women with sepsis or obliterative vascular disease 2, 3
• Careful monitoring is required when any uterotonic is used due to potential hemodynamic effects 1