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Pharmacology: Pharmacodynamics: Bromocriptine mesylate is an ergot-derivative dopamine receptor agonist and prolactin inhibitor. Bromocriptine reduces serum prolactin concentrations by inhibiting release of prolactin from the anterior pituitary gland by a direct effect on the pituitary and/or by stimulating postsynaptic dopamine receptors in hypothalamus to release prolactin inhibitory factor via a complicated catecholamine pathway.
Pharmacokinetics: Absorption: Bromocriptine is rapidly absorbed from the gastrointestinal tract and peak plasma concentrations occur within 1 to 3 hours after oral doses. However, only about 30% of an oral dose is absorbed and, owing to extensive first-pass metabolism, the bioavailability is only about 6%.
Distribution: Bromocriptine and its metabolites do not distribute appreciably into erythrocytes. In vitro studies have found that bromocriptine is 90-96% bound to serum albumin.
Metabolism: Bromocriptine is extensively metabolized in the gastrointestinal tract and liver, principally by cytochrome P-450 (CYP) 3A4. The metabolites apparently are not pharmacologically active or toxic.
Excretion: Bromocriptine and its metabolites are excreted principally in feces via billiary elimination; approximately 2.5-5.5% of a single dose is excreted in urine. Within 5 days, about 85% of a dose is excreted in feces.
