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Pharmacology · Ergot alkaloids

Methylergometrine !

Ergot derivative that causes a strong, sustained contraction of the uterus after the placenta is delivered. It raises blood pressure: never in pre-eclampsia.

Updated 2026-11-01

  • Class: Ergot alkaloids
  • Receptor: Serotonin 5-HT2 and alpha-adrenergic receptors of the myometrium
  • ATC code: G02AB01

Also called: Methylergonovine

The crystal shows methylergometrine bound to the human serotonin 5-HT2B receptor. Its uterine effect involves related 5-HT2 and alpha-adrenergic receptors of the myometrium.

Target in 3D: Serotonin 5-HT2 and alpha-adrenergic receptors of the myometrium. PDB structure 6DRY (RCSB PDB, public domain). View the structure at RCSB PDB

Mechanism of action

Methylergometrine acts directly on uterine smooth muscle through serotonin and alpha-adrenergic receptors. It raises the tone, rate and strength of contractions and produces a sustained contraction that compresses the vessels and reduces blood loss. The same action on vascular smooth muscle causes vasoconstriction and high blood pressure.

  1. It stimulates 5-HT2 and alpha-adrenergic receptors of the myometrium
  2. Uterine tone rises and the contraction is sustained
  3. Placental bed vessels are compressed and bleeding falls
  4. On vessels: vasoconstriction and higher blood pressure

Pharmacokinetics

Absorption
Given IM, IV (slowly) or by mouth; about 60% oral bioavailability
Metabolism
Liver, through CYP3A4
Elimination
Mainly by the liver, with some renal excretion
Half-life
About 3.4 hours after IM use, with wide variation
Onset and duration
Immediate IV, 2–5 minutes IM and 5–10 minutes by mouth

Indications

Adverse effects

Common

  • High blood pressure, sometimes with headache
  • Nausea, vomiting and abdominal pain
  • Low blood pressure
  • Chest pain and palpitations

Contraindications

  • Hypertension
  • Pre-eclampsia and eclampsia
  • Pregnancy (before birth)
  • Hypersensitivity
  • Use with strong or moderate CYP3A4 inhibitors

Key interactions

Strong CYP3A4 inhibitors (clarithromycin, erythromycin, HIV protease inhibitors, ketoconazole, itraconazole)
Higher levels with severe vasospasm and ischaemia; do not combine
CYP3A4 inducers (rifampicin, carbamazepine, phenytoin)
Lower levels and a weaker effect
Beta-blockers and other vasoconstrictors
Greater vasoconstriction
Nitroglycerin and other antianginal drugs
Methylergometrine opposes their effect

What is monitored

  • Blood pressure before and after each dose
  • Uterine tone and blood loss
  • Chest pain, headache and vision changes
  • Colour, temperature and pulses of hands and feet (vasospasm)

Administration and safety

  • Check blood pressure before giving it; it is not used if the patient is hypertensive or has pre-eclampsia.
  • IV use is not routine; when essential, it is injected slowly while blood pressure is watched. Avoid intra-arterial injection.
  • Store refrigerated and protected from light; use only if the solution is clear and colourless.
  • Store apart from newborn medicines: it has been given to newborns by mistake.

Nursing care

  • Before the dose: blood pressure and a history of hypertension, pre-eclampsia or heart disease.
  • After the dose: recheck blood pressure, uterine tone and lochia.
  • Ask about chest pain, severe headache, numb or cold fingers.
  • Review the medicine list for macrolides, protease inhibitors or azole antifungals.
  • Teaching: breastfeeding is paused during treatment and for a short time after the last dose, as the label states.

Pregnancy and breastfeeding

Contraindicated before birth because it contracts the uterus; it is used only after delivery of the placenta (or of the anterior shoulder).

Test yourself

Think of the answer, then tap the question to see it.

What must be checked before giving methylergometrine?

Blood pressure: it is contraindicated in hypertension and pre-eclampsia because it causes vasoconstriction.

Why is methylergometrine dangerous with clarithromycin?

Clarithromycin inhibits CYP3A4; methylergometrine levels rise and cause severe vasospasm and ischaemia.

Why should methylergometrine not be given IV routinely?

A fast IV dose can cause sudden hypertension and stroke; when IV use is essential it is given slowly with blood pressure checks.

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Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.

Sources: DailyMed - METHYLERGONOVINE MALEATE injection, solution (DailyMed (U.S. National Library of Medicine), 2026); WHO recommendations: uterotonics for the prevention of postpartum haemorrhage (World Health Organization, 2018); ATCDDD - ATC/DDD Index (WHO Collaborating Centre for Drug Statistics Methodology, 2026).

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