Gastric emptying: the validity of the paracetamol absorption test adjusted for individual pharmacokinetics

An algorithm for the paracetamol absorption test for gastric emptying, adjusting for individual pharmacokinetics, was recently developed. The aim of the present study was to validate the use of this algorithm. Furthermore, the algorithm was applied to elucidate whether a gastric tube interferes with the rate of gastric emptying. A caloric liquid meal with paracetamol was administered orally to nine healthy volunteers on two separate days. On one occasion, the subjects were intubated with a nasogastric tube and the meal was aspirated from the stomach 45 min after meal intake. The percentage of the meal retained in the stomach at the time of aspiration was determined by analyses of paracetamol in the aspirate and compared with calculations by the algorithm. On the other examination day, the same meal was ingested without tube and aspiration. The median percentage of the meal retained in the stomach at aspiration was 47% (range 33-70%) calculated by the algorithm and 48% (range 23-61%) based on the aspiration data. The correlation between the emptying parameters was r=0.97 (P < 0.001). The median of gastric emptying parameters was similar when the number of samples included in the calculation by the algorithm was reduced, but the range tended to increase. The gastric tube moderately inhibited gastric emptying during the period 20-40 min after meal intake (P < 0.05), but for the period from meal intake until start of aspiration, no inhibition was found. The present study demonstrates that the novel algorithm for the paracetamol absorption test provides valid estimates for gastric emptying.