A homolog of ergonovine containing one more CH2 group. (Merck Index, 11th ed)
Indication
For the prevention and control of excessive bleeding following vaginal childbirth
Pharmacology
Methylergonovine is a semisynthetic ergot alkaloid and a derivative of ergonovine and is used for the prevention and control of postpartum and post-abortion hemorrhage. In general, the effects of all the ergot alkaloids appear to results from their actions as partial agonists or antagonists at adrenergic, dopaminergic, and tryptaminergic receptors. The spectrum of effects depends on the agent, dosage, species, tissue, and experimental or physiological conditions. All of the alkaloids of ergot significantly increase the motor activity of the uterus. After small doses contractions are increased in force or frequency, or both, but are followed by a normal degree of relaxation. As the dose is increased, contractions become more forceful and prolonged, resting tonus is markedly increased, and sustained contracture can result.
Toxicity
Signs and symptoms of overexposure: hypertension, seizures, headache, hypotension, nausea, and vomiting.
Affected Organisms
Humans and other mammals
Biotransformation
Hepatic, with extensive first-pass metabolism.
Absorption
Absorption is rapid after oral (60% bioavailability) and intramuscular (78% bioavailability) administration.
Half Life
3.39 hours
Elimination
Ergot alkaloids are mostly eliminated by hepatic metabolism and excretion, and the decrease in bioavailability following oral administration is probably a result of first-pass metabolism in the liver.
