Ergonovine (Ergotrate) and methylergonovine (Meth-ergine) are compounds obtained either directly or semi-synthetically from ergot, a fungus that grows on rye and other grains. These compounds stimulate uterine smooth muscle directly, thereby increasing muscular tone and enhancing the rate and force of rhythmical contractions. Ergonovine also stimulates cervical contractions. These drugs are capable of inducing a sustained tetanic contraction, which can shorten the final stage of labor and aid in the reduction of postpartum blood loss. Both are commonly used for the routine expulsion of the placenta after delivery and in postpartum and postabortal atony and hemorrhage.
Both drugs are partial agonists at a-adrenergic receptors and at some serotonin and dopamine receptors; they also can inhibit the release of endothelial-derived relaxation factor. They may induce arterial vasoconstriction and have minor actions on the central nervous system. Their a-adrenergic blocking activity is relatively weak compared with those of other ergot alkaloids.
Absorption is rapid and largely complete after oral administration, and onset of action occurs in 5 to 15 minutes and lasts about 3 hours. Both ergonovine and methylergonovine can be given intramuscularly or intravenously, although intravenous administration can be associated with transient but severe hypertension. These compounds undergo hepatic metabolism, with elimination primarily by renal excretion of metabolites. They also can be found in breast milk, and therefore, neither drug should be administered longer than necessary, since prolonged use can lead to ergot poisoning (ergotism), including gangrene, in the nursing infant.
Adverse reactions associated with their administration include hypertension, headache, and possible seizures. Nausea, vomiting, chest pains, difficulties in breathing, and leg cramps also have been reported. These alkaloids should not be used in cases of threatened spontaneous abortion or in patients with known allergies to the drugs. Contraindications generally include angina pectoris, myocardial infarction, pregnancy, and a history of a cerebrovascular accident, transient ischemic attack, or hypertension.
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