Effect of intravenous omeprazole on intragastric pH during intravenous infusion of amino acids

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Intravenous amino acids stimulate gastric acid secretion by an unknown mechanism. In patients on parenteral nutrition, this amino acid-induced gastric acid secretion might contribute to the failure of H2-receptor antagonists to raise intragastric pH above 4.0, a level thought to be needed to prevent stress ulceration. Therefore we studied the effect of single and repeated doses of the H+/K(+)-ATPase blocker omeprazole on the intragastric pH during a 3-hr infusion of amino acids in 10 healthy volunteers; 5% glucose was used as a control infusion. Amino acids significantly decreased intragastric pH when compared to glucose infusion (P less than 0.05). After intravenous administration of 40 mg, 80 mg and 2 X 40 mg omeprazole, this amino acid-induced fall in pH was significantly inhibited (P less than 0.01). No advantage of the 80-mg dose over the 40-mg dose could be demonstrated. The repeated dose of 40 mg showed a tendency to higher pH values compared to the single-dose experiments, which reached significance in the amino acid experiments only (P less than 0.05). Neither during the infusion of amino acids nor the glucose infusion omeprazole was able to continuously raise intragastric pH above 4.0. In conclusion, this study shows that intravenous omeprazole prevents gastric acid stimulation by intravenous amino acids but fails to continuously raise intragastric pH above 4.