Regular use of H2 blockers reduces the efficacy of roxatidine to control gastric pH and volume

Abstract

H(2) antagonist premedication is common in surgical patients to control gastric pH and volume. However, several reports suggest that long-term medication may produce tolerance. Therefore, we studied the efficacy of a preanesthetic H(2) antagonist (oral roxatidine) in patients on regular H(2) antagonist therapy. Forty-eight patients undergoing elective surgery were studied and grouped according to medication: those on no medication (control group) and those receiving H(2)-antagonists for less than two weeks (< or =2 w group), between two and four weeks (2-4 w group) and for longer than four weeks (> or =4 w group; n =12 each). All patients were given oral roxatidine as anesthetic premedication. Gastric volume and pH were measured after induction of anesthesia. Arterial blood was simultaneously collected for measurement of plasma gastrin levels using an enzyme-linked immunosorbent assay We observed a significant decrease and increase in, respectively, gastric pH and volume (mL) in the < or =2 w group [6.50 +/- 0.43 (NS) and 11.6 +/- 10.3 (NS)], 2-4 w group [4.77 +/- 2.11 (P < 0.01) and 14.1 +/- 10.8 (P < 0.05)], > or =4 w group [2.32 +/- 1.46 (P < 0.01) and 22.2 +/- 14.2 (P < 0.01)] compared to patients in the control group (6.35 +/- 1.32 and 4.9 +/- 4.7). Plasma gastrin levels were decreased with increasing time on medication with a significant difference (46%) observed after two weeks' treatment. In addition, there was a significant correlation between gastric pH and plasma gastrin levels (r = 0.43, P < 0.01). These data suggest that regular H(2) antagonist treatment for longer than two weeks may produce tolerance to pre-anesthetic H(2) antagonist administration.