Evaluation of acetaminophen absorption in horses with experimentally induced delayed gastric emptying

Objective-To evaluate the correlation between the half-time of liquid-phase gastric emptying (T-50) determined by use of nuclear scintigraphy, using technetium Tc 99m pentetate, and absorption variables of orally administered acetaminophen in horses with experimentally delayed gastric emptying. Animals-6 mature horses. Procedure-Delayed gastric emptying was induced by IV injection of atropine sulfate. Twenty minutes later, acetaminophen and technetium Tc 99m pentetate were administered simultaneously via nasogastric tube. Serial lateral images of the stomach region were obtained, using a gamma camera. Power exponential curves were used for estimation of T-50 and modified R-2 values for estimation of goodness-of-fit of the data. Serial serum samples were obtained, and acetaminophen concentration was determined, using fluorescence polarization immunoassay. Maximum serum concentration (C-max), time to reach maximum serum concentration (T-max), area under the curve for 480 minutes, and the appearance rate constant were determined, using a parameter estimation program. Correlations were calculated, using a Spearman rank correlation coefficient. Results-A significant correlation was detected between T-50 determined by use of scintigraphy and T-max determined by use of acetaminophen absorption. Correlation between T-50 and other absorption variables of acetaminophen was not significant. Conclusions and Clinical Relevance-The acetaminophen absorption method was a valid technique in this model of delayed gastric emptying in horses. The method may be a valuable tool for use in research as well as in clinical evaluation of gastric emptying in horses.