Pharmacokinetics
The absorption of omeprazole takes place in the small intestine and is usually completed within 3–6 hours. The systemic bioavailability of omeprazole after repeated dose is about 60%.
Omeprazole bioavailability is significantly impaired by the presence of food and, therefore, patients should be advised to take omeprazole with a glass of water on an empty stomach (i.e., fast for at least 60 minutes before taking omeprazole). Additionally, most sources recommend that after taking omeprazole at least 30 minutes should be allowed to elapse before eating (at least 60 minutes for immediate-release omeprazole plus sodium bicarbonate products, such as Zegerid), though some sources say that with delayed-release forms of omeprazole it is not necessary to wait before eating after taking the medication. Plasma protein binding is about 95%.
Omeprazole is completely metabolized by the cytochrome P450 system, mainly in the liver. Identified metabolites are the sulfone, the sulfide and hydroxy-omeprazole, which exert no significant effect on acid secretion. About 80% of an orally given dose is excreted as metabolites in the urine and the remainder is found in the feces, primarily originating from bile secretion.
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