Comparison of nuclear scintigraphy and acetaminophen absorption as a means of studying gastric emptying in horses

Objective-To evaluate the correlation between half-time of liquid-phase gastric emptying (T-50), determined with nuclear scintigraphy using technetium Tc 99m pentetate, and absorption variables of orally administered acetaminophen. Animals-6 mature horses. Procedure-Technetium Tc 99m pentetate (10 mCl) and acetaminophen (20 mg/kg of body weight) were administered simultaneously in 200 mi of water. Serial left and right lateral images of the stomach region were obtained with a gamma camera, and T-50 determined separately for counts obtained from the left side, the right side and the geometric mean. 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 taken, 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 240 minutes and the absorption constant (K-a) were determined, using a parameter estimation program. Correlations were calculated, using the Spearman rank correlation coefficient. Results-Correlations between T-50 and T-max and between T-50 and K-a were significant. Conclusions and Clinical Relevance-T-max and K-a are valuable variables in the assessment of liquid-phase gastric emptying using acetaminophen absorption. Acetaminophen absorption may be a valuable alternative to nuclear scintigraphy in the determination of gastric emptying rates in equine patients with normally functioning small intestine.