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Pharmacology: Pharmacodynamics: Esomeprazole a proton pump inhibitor, is the S-isomer of omeprazole.
Esomeprazole is a weak base and is concentrated and converted to the active form in the highly acidic environment of the secretory canaliculi of the parietal cell.
It specifically inhibits the enzyme H+/K+-ATPase in the acid pump and inhibits both basal and stimulated acid secretion. Esomeprazole blocks the final step in acid production, resulting in potent, long-lasting inhibition of gastric and secretion.
Pharmacokinetics: Distribution: The apparent volume of distribution as steady state in healthy subject is approximately 16 L. Esomeprazole is 97% plasma protein bound.
Metabolism and excretion: Esomeprazole is completely metabolized by the cytochrome P450 (CYP) isoenzyme CYP2C19 and the remainder is metabolized by the cytochrome P450 (CYP) isoenzyme CYP3A4. The major metabolites of esomeprazole have no effect on gastric acid secretion. The plasma elimination half-life is about 1.3 hours.
Esomeprazole is completely eliminated from plasma between doses with no tendency for accumulation during once daily administration.
