<p>Esomeprazole is a proton pump inhibitor that suppresses gastric acid secretion by specific inhibition of the H+/K+-ATPase in the gastric parietal cell. Esomeprazole (S-isomer of omeprazole) is the first single optical isomer of proton pump inhibitor, provides better acid control than racemic proton pump inhibitors.<br />
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<strong>Absorption</strong>: Esomeprazole capsules contain an enteric-coated pellet formulation of esomeprazole magnesium. After oral administration peak plasma levels (Cmax) occur at approximately 1.5 hours (Tmax). The Cmax&nbsp;increases proportionally when the dose is increased, and there is a three-fold increase in the area under the plasma concentration-time curve (AUC) from 20 to 40 mg. At repeated once daily dosing, the systemic bioavailability is approximately 90% compared to 64% after a single dose. The AUC after administration of a single dose of esomeprazole is decreased by 33-53% after food intake compared to fasting conditions. Esomeprazole should be taken at least one hour before meals.<br />
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<strong>Distribution</strong>: Esomeprazole is 97% bound to plasma proteins. Plasma protein binding is constant over the concentration range of 2 20 mmol/L. The apparent volume of distribution at steady state in healthy volunteers is approximately 16 L.<br />
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<strong>Metabolism</strong>: Esomeprazole is extensively metabolized in the liver by the cytochrome P450 (CYP) enzyme system. The metabolites of esomeprazole lack anti-secretory activity. The major part of esomeprazole&rsquo;s metabolism is dependent upon the CYP2C19 isoenzyme, which forms the hydroxy and desmethyl metabolites. The remaining amount is dependent on CYP3A4 which forms the sulphone metabolite.<br />
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<strong>Excretion</strong>: The plasma elimination half-life of esomeprazole is approximately 1&ndash;1.5 hours. Less than 1% of parent drug is excreted in the urine. Approximately 80% of an oral dose of esomeprazole is excreted as inactive metabolites in the urine, and the remainder is found as inactive metabolites in the faeces.<br />
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<strong>Combination Therapy with Antimicrobials</strong>: Esomeprazole magnesium 40 mg once daily is given in combination with clarithromycin 500 mg twice daily and amoxicillin 1000 mg twice daily for 7 days. The mean steady state AUC and Cmax of Esomeprazole increased by 70% and 18%, respectively, during triple combination therapy compared to treatment with Esomeprazole alone. The pharmacokinetic parameters for clarithromycin and amoxicillin are similar during triple combination therapy and administration of each drug alone. However, the mean AUC and Cmax for 14-hydroxyclarithromycin are increased by 19% and 22%, respectively, during triple combination therapy compared to treatment with clarithromycin alone. This increase in exposure to 14-hydroxyclarithromycin is not considered to be clinically significant.</p>