Metvex Mechanism of Action

Pharmacology: Pharmacokinetics: Metoclopramide is rapidly and almost completely absorbed from the gastrointestinal tract following a dose by mouth, although conditions such as vomiting or impaired gastric motility may reduce absorption. However, it undergoes hepatic first pass metabolism, which varies considerably between subjects, and hence absolute bioavailability and plasma concentrations are subject to wide inter individual variation. On average, the bioavailability of oral metoclopramide is about 75%, but it varies between about 30 to 100%. Peak plasma concentrations of metoclopramide occur about 1 to 2 hours after an oral dose. Bioavailability is equally variable following rectal or intranasal administration, although it may be somewhat better if the drug is given intramuscularly.
Metoclopramide is widely distributed in the body with an apparent volume of distribution of about 3.5 liters per kg. It readily crosses the blood-brain barrier into the CNS. It also freely crosses the placenta, and has been reported to attain concentrations in fetal plasma about 60 to 70% of those in maternal plasma. Concentrations higher than those in maternal plasma may be reached in the breast milk of lactating mothers, particularly in the early puerperium, although concentrations decrease somewhat in the late puerperium. Elimination of metoclopramide is biphasic, with a terminal elimination half-life of about 4 to 6 hours although this may be prolonged in renal impairment, with consequent elevation of plasma concentrations. It is excreted in the urine, about 85% of a dose being eliminated in 72 hours, 20 to 30% unchanged metoclopramide and the remainder as sulfate or glucuronide conjugates, or as metabolites. About 5% of a dose is excreted in faeces via the bile.