Why is methylergometrine (Pregnancy-Induced Hypertension) PIH contraindicated?

Why Methylergometrine is Contraindicated in Pregnancy-Induced Hypertension

Methylergometrine is contraindicated in pregnancy-induced hypertension because it causes vasoconstriction and hypertension in more than 10% of patients, which can precipitate life-threatening complications including stroke and cerebrovascular accidents in women who already have elevated blood pressure. 1

Mechanism of Harm

Methylergometrine (also called methylergonovine) is an ergot alkaloid that causes:

• Significant vasoconstriction leading to acute blood pressure elevation 1
• Risk exceeding 10% for inducing hypertensive episodes 1
• Potential for cerebrovascular accidents when administered to hypertensive patients 2

The FDA drug label explicitly warns that this medication can induce "sudden hypertensive and cerebrovascular accidents," particularly with intravenous administration 2. In women with PIH who already have compromised vascular function and elevated blood pressure, adding a potent vasoconstrictor creates a dangerous synergy.

Clinical Context in Postpartum Hemorrhage Management

While methylergometrine is commonly used to prevent postpartum hemorrhage by promoting uterine contraction, safer alternatives exist for women with hypertension:

• Oxytocin administered as slow IV infusion (<2 U/min) is the preferred first-line agent, as it avoids systemic hypotension while controlling bleeding 1
• Prostaglandin F analogues can be used to treat postpartum hemorrhage, though they should be avoided if increased pulmonary artery pressure is undesirable 1

Specific Contraindications in PIH

The European Society of Cardiology guidelines specifically state that methylergonovine is contraindicated in the postpartum management of women with cardiovascular disease, including those with hypertensive disorders 1. This recommendation applies to:

• Pre-existing hypertension 1
• Gestational hypertension 1
• Pre-eclampsia 1
• Superimposed gestational hypertension with proteinuria 1

Additional Safety Concerns

Beyond the immediate hypertensive risk, methylergometrine carries other important warnings:

• Should not be administered IV routinely due to risk of sudden hypertensive crisis 2
• Requires slow administration (minimum 60 seconds) with careful blood pressure monitoring if IV use is deemed essential 2
• Risk of postpartum depression when used in the postpartum period, leading to recommendations to avoid methyldopa (a different drug) postpartum for similar reasons 1

Clinical Algorithm for Postpartum Hemorrhage in PIH

When managing postpartum hemorrhage in women with pregnancy-induced hypertension:

1. First-line: Use slow IV oxytocin infusion (<2 U/min) 1
2. Second-line: Consider prostaglandin F analogues if oxytocin is insufficient and pulmonary hypertension is not a concern 1
3. Avoid: Methylergometrine/methylergonovine entirely 1
4. Monitor: Blood pressure continuously during and after any uterotonic administration 1

The absolute contraindication exists because the risk of precipitating a hypertensive emergency, stroke, or cerebrovascular accident outweighs any potential benefit in controlling uterine bleeding, especially when safer alternatives are readily available.