Esomeprazole, is a new proton pump inhibitor. It is the S-isomer of omeprazole and is the first
such inhibitor to be developed as a single isomer.
- Esomeprazole reduces gastric acid secretion through aspecific targeted mechanism of action.
It’s a specific inhibitor of the acid proton pump in the parietal cell where it inhibits the enzyme
H+,K+-ATpase and inhibit both basal and stimulated acid secretion. Both the R-and S-isomer
of omeprazole have similar pharmcodynamic activity.
- Absorption of Esomeprazole is rapid with peak plasma levels occurring approximately 1-2
hours after oral dose. The absolute bioavailability is 64% after a single dose of 40mg and
increases to 89% after repeated once daily administration. For 20mg of Esomeprazole the
corresponding values are 50% and 68% respectively .The apparent volume of distribution at
steady state in healthy subjects is approximately 0.22L/kg of body weight.
- Esomeprazole is 97% plasma protein bound.
- Food intake both delays and decreases the absorption of Esomeprazole although this has
no significant influence on the effect of Esomeprazole on intragastric acidity.
- Esomeprazole is completely metabolised in the liver by the cytochrome P450 system .The
major part of the metabolism of Esomeprazole is dependent on the polymorphic CYP2C19
responsible for the formation of hydroxy and desmethyl metabolites of Esomeprazole. The
remaining part is dependent on another specific (isoform), CYP3A4, responsible for the
formation of Esomeprazole sulphone main metabolite in plasma. The major metabolites of
Esomeprazole have no effect on the gastric acid secretion.
-The plasma clearance is about 17L/h after a single dose and about 9L/h after repeated
administration. The plasma elimination half-life is about 1.3 hours after repeated once daily
-Esomeprazole is completely eliminated from plasma between doses with no tendency for
accumulation during once- daily administration
- Almost 80% of an oral dose of Esomeprazole is excreted as metabolites in urine, the
remainder in the faces. Less than 1% of the parent drug is found in urine.