Gastric emptying: the validity of the paracetamol absorption test adjustedfor individual pharmacokinetics

An algorithm for the paracetamol absorption test for gastric emptying, adju sting for individual pharmacokinetics, was recently developed. The aim of t he present study was to validate the use of this algorithm. Furthermore, th e algorithm was applied to elucidate whether a gastric tube interferes with the rate of gastric emptying. A caloric liquid meal with paracetamol was a dministered 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 b y analyses of paracetamol in the aspirate and compared with calculations by the algorithm. On the other examination day, the same meal was ingested wi thout tube and aspiration. The median percentage of the meal retained in th e stomach at aspiration was 47% (range 33-70%) calculated by the algorithm and 48% (range 23-61%) based on the aspiration data. The correlation betwee n the emptying parameters was r=0.97 (P < 0.001). The median of gastric emp tying parameters was similar when the number of samples included in the cal culation by the algorithm was reduced, but the range tended to increase. Th e gastric tube moderately inhibited gastric emptying during the period 20-4 0 min after meal intake (P < 0.05), but for the period from meal intake unt il start of aspiration, no inhibition was found. The present study demonstr ates that the novel algorithm for the paracetamol absorption test provides valid estimates for gastric emptying.