Ion-trapping of meperidine: influence of antacid treatments on serum and gastric fluid concentrations.

The ascorbic acid pretreated beagle dog was used to demonstrate the phenomenon of ion-trapping and the influence of three different antacid treatments on the serum and gastric fluid concentration of meperidine: pretreatment with magnesium-aluminum hydroxide (MA), pretreatment with cimetidine (C), and periodic total aspiration of gastric fluid (ASP). A significant correlation between pH and the meperidine concentration in gastric fluid was found; the lower the pH the higher is the secretion of meperidine into gastric fluid. The gastric fluid meperidine concentrations were 8-30 times as high as the respective serum concentrations. No significant differences between the meperidine concentration in the gastric fluid were found among the three treatments, MA, C, or ASP, versus control. Meperidine serum concentrations differed significantly versus control on two times for MA and on one time for ASP. The elimination half-life [h] and the mean residence time [h] differed significantly in the MA treatment (1.15 +/- 0.02 h and 1.23 +/- 0.24 h) versus control (1.90 +/- 0.19 h and 2.00 +/- 0.15 h).(ABSTRACT TRUNCATED AT 250 WORDS)