Esomep Mechanism of Action

Pharmacology: Pharmacodynamics: Esomeprazole is the S-isomer of omeprazole. It is a proton pump inhibitor which reduced gastric acid secretion through inhibition of H+ AC+-ATPase in gastric parietal cells. By inhibiting the functioning of this enzyme, the drug prevents formation of gastric acid.
Pharmacokinetics: Esomeprazole is rapidly absorbed following oral administration, with peak plasma levels occurring after approximately 1 to 2 hours. It is acid labile and an enteric-coated formulation has been developed. Bioavailability of esomeprazole increases with both dose and repeated administration to about 68% to 69% for doses of 20 and 40 mg respectively. Food delays and decreases the absorption of esomeprazole, but this does not significantly change its effect on intragastric acidity. Esomeprazole is about 97% bound to plasma proteins. It is extensively metabolized in the liver by the cytochrome P450 isoenzyme CYP2C19 to hydroxyl and desmethyl metabolites, which have no effect on gastric acid secretion. The remainder is metabolized by the cytochrome P450 isoenzyme CYP3A4 to esomeprazole sulfone. With repeated administration, there is decrease in first pass metabolism and systemic clearance, probably caused by an inhibition of the CYP2C19 isoenzyme. However, there is no accumulation during once daily use. The plasma elimination half-life is about 1.3 hours. Almost 80% of an oral dose is eliminated as metabolites in the urine, the remainder in the feces.