[The validity of serum acetaminophen concentration at 45 min as an index of gastric emptying rate: a study based on pharmacokinetic theories].

The reliability of the serum acetaminophen (APAP) concentration at 45 min (C45) as a measure of gastric emptying (GE) has been evaluated using a pharmacokinetic simulation work. The present results have revealed that C45 is a useful index to conveniently detect delayed GE, but it is unreliable to measure rapid GE. In addition, the following simple criteria for diagnosis of delayed GE has been proposed based on the pharmacokinetic theories: after ingestion of 20 mg/kg APAP dissolved in a 200 kcal-containing liquid meal, 1) the delayed GE is excluded when C45 > 5.0 micrograms/ml, 2) whether GE is delayed or not is inconclusive when 2.0 < C45 < 5.0 micrograms/ml, and 3) the delayed GE is confirmed when C45 < 2.0 micrograms/ml.