Mep-40 Mechanism of Action

Pharmacology: Pharmacodynamics and Pharmacokinetics: Omeprazole belongs under a class of drugs called proton pump inhibitors. Omeprazole blocks or inhibits gastric acid secretion. It reduces gastric acid secretion by inhibiting the enzyme system of hydrogen-potassium adrenaline triphosphate, which is regarded as the acid proton pump of the gastric parietal cells. Also called H+/K+-ATPase, the enzyme responsible for the exchange of hydrogen and potassium ions during the formation of hydrochloric acid.
It is rapidly but variably absorbed following oral administration. Omeprazole is acid-labile and pharmacokinetics may vary between the various formulations developed to improve oral bioavailability. The absorption of omeprazole is not affected by food and appears to be dose dependent; increasing the dosage above 40 mg has been reported to increase the plasma concentrations in a non-linear fashion because of saturable first-pass hepatic metabolism. Absorption is also higher after long-term administration.
Following absorption, omeprazole is almost completely metabolized in the liver, primarily by the cytochrome P450 isoenzyme CYP2C19 to form hydroxyomeprazole, and to a small extent by CYP3A4 to form omeprazole sulfone. The metabolites are inactive, and are excreted mostly in the urine and to a lesser extent in bile. The elimination half-life from plasma is reported to be about 0.5 to 3 hours. Omeprazole is highly bound (about 95%) to plasma proteins.