ergometrine brands

Molecular formula: C19H23N3O2

Ergonovine directly stimulates the uterine muscle to increase force and frequency of contractions. With usual doses, these contractions precede periods of relaxation; with larger doses, basal uterine tone is elevated and these relaxation periods will be decreased. Contraction of the uterine wall around bleeding vessels at the placental site produces hemostasis. Ergonovine also induces cervical contractions. The sensitivity of the uterus to the oxytocic effect is much greater toward the end of pregnancy. The oxytocic actions of ergonovine are greater than its vascular effects. Ergonovine, like other ergot alkaloids, produces arterial vasoconstriction by stimulation of alpha-adrenergic and serotonin receptors and inhibition of endothelial-derived relaxation factor release. It is a less potent vasoconstrictor than ergotamine. As a diagnostic aid (coronary vasospasm), ergonovine causes vasoconstriction of coronary arteries. Ergonovine maleate and methylergonovine maleate are pharmacologically similar. Both drugs directly stimulate contractions of uterine and vascular smooth muscle. Following administration of usual therapeutic doses of ergonovine or methylergonovine, intense contractions of the uterus are produced and are usually followed by periods of relaxation. Larger doses of the drugs, however, produce sustained, forceful contractions followed by only short or no periods of relaxation. The drugs increase the amplitude and frequency of uterine contractions and uterine tone which in turn impede uterine blood flow. Ergonovine and methylergonovine also increase contractions of the cervix. Ergonovine and methylergonovine produce vasoconstriction, mainly of capacitance vessels; increased central venous pressure, elevated blood pressure, and, rarely, peripheral ischemia and gangrene may result. Methylergonovine reportedly may interfere with prolactin secretion, but this effect has not been definitely established. ... The effect of /Ergonovine/ on isolated canine tracheobronchial smooth muscle was analyzed to investigate the mechanism of ergonovine-induced airway smooth muscle contraction. Both ergonovine and serotonin (5-hydroxytryptamine, 5HT) contracted canine tracheal smooth muscle with EC50 1.4 X 10(-8) M and 5.1 X 10(-7) M, respectively. The maximal contractile response observed with ergonovine was approximately 30% less than that observed with 5HT. In diverse blockers such as methysergide, atropine, prazosin, propranolol, pyrilamine and cimetidine, only methysergide competitively blocked both ergonovine and 5HT responses with a similar calculated dissociation constant (pKB); 8.3 +/- 0.2 against ergonovine and 8.5 +/- 0.2 against 5HT (n = 6, p = 0.9). The relative affinity and efficacy of ergonovine and 5HT were determined by use of a partial irreversible antagonist, phenoxybenzamine. The calculated affinity of ergonovine was about 16 times higher than that of 5HT. The relative efficacy of EC100 for ergonovine was 0.2 but at EC10 it was 41.9 (5HT efficacy = 1). Ergonovine 10(-9) M or 10(-8) M shifted the 5HT dose-response curve to the right without reducing the maximal response, but the shift was nonparallel. Ergonovine and 5HT also contracted canine bronchial smooth muscle in a dose dependent manner with EC50 6.4 X 10(-8) M and 1.8 X 10(-7) M, respectively. The dose-responses curve of these two agonists were competitively blocked by methysergide 10(-6) M. These data indicate that ergonovine directly contracts canine tracheobronchial smooth muscle as a result of its combination with 5HT receptors. ... Although commonly classified as alpha-adrenergic blocking agents, most important effects of all ergot alkaloids are due to action on CNS and direct stimulation of smooth muscle. Latter occurs in many different organs... In some organs stimulation ... shown to be due to action on same receptors involved in responses to catecholamines. Thus ergot alkaloids can be considered to be series of partial agonists with blocking activity...

Source: PubChem (NCBI) · compound 443884