Sign Out
Pharmacology: Omeprazole is a proton pump inhibitor. It inhibits secretion of gastric acid by irreversibly blocking the enzyme system of hydrogen/potassium adenosine triphosphate (H+/K+ ATPase), the "proton pump" of the gastric parietal cells.
Pharmacokinetics: The absorption of Omeprazole appears to be dose dependent; increasing the dosage above 40 mg has been reported to increase the plasma concentrations. In addition, absorption is higher after long term administration. Bioavailability of Omeprazole may be increased in elderly patients, in some ethnic groups such as Chinese, and in patients with impaired hepatic function, but it is not markedly affected in patients with renal impairment. Following absorption, Omeprazole is almost completely metabolized in the liver, primarily by the cytochrome P450 isoenzyme CYP2C19 to form hydroxyomeprazole to a small extent by CYP3A to form Omeprazole sulfone. The metabolites are inactive, and are excreted mostly in the urine and to a lesser extent to the 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.
