A RELIABLE AND CONVENIENT PARAMETER OF THE RATE OF PARACETAMOL ABSORPTION TO MEASURE GASTRIC-EMPTYING RATE OF LIQUIDS

The rate of paracetamol absorption represents gastric emptying rate (G ER) of liquids, Thus, the liquid GER is assessed by conventional pharm acokinetic parameters such as the maximum concentration and the time t o maximum concentration after oral administration of paracetamol. Howe ver, the conventional parameters are subject not only to the rate but also to the extent of absorption. For the reliable assessment of GER w e have proposed a new parameter, the C-0.5/C-0.25 ratio, for the rate of paracetamol absorption without being affected by the extent of abso rption. Of 15 healthy male volunteers, 9 orally received 10 mg/kg of p aracetamol with 200 mi of water as the ''normal'' GER group, and the o ther 6 took 10 mg/kg of paracetamol with 200 mi of a liquid nutrient ( 200 kcal/200 mi), which delays GER, as the ''delayed'' GER group. Bloo d samples were obtained at t = 0 (pre-dose), 0.25, 0.5, 0.75, 1.0, 1.5 , 2.0, 3.0, 4.0, 6.0, and 8.0 hours (post-dose). In each subject, GER was assessed by the conventional parameters, the C-0.5/C-0.25 ratio, a nd the Wagner-Nelson method which provides an accurate estimate of the drug absorption rate. Using the C-0.5/C-0.25 ratio and the Wagner-Nel son method we could more clearly differentiate the delayed GER group f rom the normal GER group than by using the conventional parameters. Th is suggests that the C-0.5/C-0.25 ratio and the Wagner-Nelson method m ay be more reliable than the conventional parameters in detecting a de lay in GER. Further, it should be noted that the C-0.5/C-0.25 ratio ca n be calculated from only 2 blood samples while the Wagner-Nelson meth od requires repeated blood sampling.