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Ergot Alkaloids

Secale cornutum

For medical students2 min readUpdated 2026-10-10

Ergot alkaloids are a group of plant-derived pharmacological agents obtained from the sclerotium of the fungus Claviceps purpurea. They induce powerful and sustained tonic contractions of the myometrium, making them highly effective for stopping uterine bleeding.

SourceThe fungus *Claviceps purpurea* on rye (*Secale cornutum*)
Effect on UterusSustained tonic contraction of the myometrium
Primary IndicationArrest of uterine hemorrhage
ToxicityRisk of ergotism and gangrene upon poisoning

Classification and General Characteristics

In pharmacology, agents that increase myometrial tone through sustained tonic contraction are divided into ergot alkaloids and synthetic drugs. Ergot alkaloids include ergometrine (ergonovine) and ergotamine.

The raw material source is the sclerotium of the fungus Claviceps purpurea, which parasitizes rye (Secale cornutum). The main mechanism of hemostasis when using these agents involves the mechanical compression of blood vessel walls by the contracted muscle fibers of the uterus.

Pharmacodynamics and Clinical Application

These medicinal substances have narrow but critically important applications in medical practice. The main indications include:

An absolute contraindication for prescribing these agents is accelerating labor. Spasm of the myometrium during labor inevitably leads to fetal asphyxia.

Ergometrine and Ergotamine: Drug Profiles

Ergometrine is a natural alkaloid that acts as a $5-HT_{2A}$ receptor agonist (serotonin). An interesting feature of the drug is its effect on lactation: it inhibits prolactin secretion, thereby suppressing milk production. Side effects include headache, hallucinations, nausea, diarrhea, and abdominal pain.

Ergotamine is used in obstetrics similarly to ergometrine, but it possesses unique vascular effects. It reduces the amplitude of cranial artery pulsations, making it useful for treating migraines and vascular headaches.

Toxicology: Ergotism and Synthetic Analogs

Prolonged or excessive use of ergot causes severe poisoning known as ergotism. Symptoms include vivid hallucinations, nausea, vomiting, and diarrhea. Vascular disruptions in ergotism manifest as sustained peripheral vasospasm combined with endothelial damage, carrying a high risk of gangrene.

The group of agents affecting uterine tone and hemostasis also includes cotarnine chloride (stypticin), a synthetic dihydroisoquinoline derivative. It can be administered orally, parenterally, or topically as a 1–2% aqueous solution to stop minor bleeding.

Mnemonic

Ergometrine is for the metra (uterus), while ergotamine treats head-aches (migraines in the cranium).

Frequently asked questions

Which receptor types do ergot alkaloids interact with?

Ergot alkaloids and their derivatives interact with serotonin and adrenergic receptors.

  • Serotonin receptors — ergometrine is a $5-HT_{2A}$ receptor agonist, while ergotamine and dihydroergotamine stimulate 5-HT receptors, particularly the $5-HT_{1D}$ subtype.
  • $\alpha$-Adrenoceptors — natural alkaloids and dihydrogenated derivatives possess $\alpha$-adrenoreceptor blocking activity; dihydroergotamine exhibits blockade of $\alpha_1$- and $\alpha_2$-adrenoceptors.
What are the clinical manifestations of ergot poisoning (ergotism)?

Clinical manifestations of ergotism include severe damage to the central nervous system, gastrointestinal tract, and vasculature.

  • Acute form — symptoms of gastroenteritis, paresthesia, seizures, vivid hallucinations, nausea, vomiting, and diarrhea.
  • Chronic form — crawling sensations in the extremities (paresthesias), vomiting, GI disturbances, and potential infertility.

There are three clinical forms of the disease:

  • Convulsive — toxic tonic contractions of flexor muscles lasting about a month.
  • Gangrenous — persistent vasospasm and endothelial damage cause necrosis of peripheral extremities accompanied by severe pain.
  • Mixed.
What contraindications exist for the use of ergot alkaloids, aside from labor stimulation?

For ergometrine, pregnancy and the intrapartum period prior to the delivery of the placenta are contraindicated.

Which drugs belong to the group of dihydrogenated ergot alkaloids?

The group of dihydrogenated ergot alkaloids comprises non-selective $\alpha$-blockers derived from D-lysergic acid. This group includes the following drugs:

  • Dihydroergotamine — used as a nasal spray to abort migraine attacks.
  • Dihydroergotoxine — a representative of non-selective $\alpha$-adrenoceptor blockers.
  • Dihydroergocryptine — used as a component of the combination drug Vasobral for treating vascular disorders.
Why are ergot alkaloids contraindicated during labor?

They cause a sustained tonic contraction of the myometrium rather than rhythmic labor contractions. Such a spasm occludes blood flow and leads to fetal asphyxia.

What is the mechanism of arresting bleeding when they are used?

Hemostasis is achieved through the mechanical compression of blood vessels by the walls of the contracted uterine muscle fibers.

How does ergometrine affect breastfeeding?

Ergometrine suppresses prolactin secretion, which inhibits the production of breast milk.

What is the specific medical application of ergotamine outside of obstetrics?

Ergotamine reduces the amplitude of cranial artery pulsations, which is why it is used to abort migraine attacks and vascular headaches.

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