Retention of acetaminophen in an in vitro model of solid-phase gastric emptying of animals

OBJECTIVE: To apply an in vitro model for assessment of the solid-phase binding capacity of acetaminophen and thus assess the reliability of this marker for evaluation of solid-phase gastric emptying in vivo in animals. SAMPLE POPULATION: 4 test meals. PROCEDURES: A spectrophotometric method for detection of acetaminophen was validated and applied for assessment of the percentage retention of acetaminophen in the solid phase of 4 test meals. The gastric milieu was simulated by incubating each meal in artificial gastric juice for 2 hours in a shaking water bath maintained at 37 degrees C. Solid-phase retention was then assessed 3 times by measuring the amount of acetaminophen that had leached into the liquid phase. RESULTS: Acetaminophen was poorly retained in the solid phase of all the test meals examined in the study. There was also a large degree of variability in the percentage retention for each meal when the experiment was repeated 3 times. CONCLUSIONS AND CLINICAL RELEVANCE: Analysis of the results of this in vitro study confirmed that acetaminophen may not be an appropriate marker of solid-phase gastric emptying. The acetaminophen gastric emptying test should be applied only for the assessment of liquid-phase emptying in animals.