Mechanism for gastric accumulation of meperidine and effect of antacid.

The effect of hydrogen ion activity (pH) on the degree of meperidine sequestration in gastric contents was studied in 15 patients. Those patients with higher gastric juice cH+ (lower pH) showed greater accumulation with time. At a cH+ more than 10,000 nmol/l, (pH < 5) concentration usually reached 100 micrograms/ml within the 60-minute period after administration of 200 mg of meperidine. When cH+ was less than 100 nmol/l (pH > 7) gastric concentrations remained low, being only slightly greater than those of plasma. Oral administration of antacid may be a practical method for preventing sequestration of meperidine in gastric juice.