Correlation betweenin vitro andin vivo drug metabolism rate: Oxidation of ethoxybenzamide in rat

In vitroand in vivocorrelations of the microsomal oxidation of drugs were examined, using ethoxybenzamide as a model drug. Ethoxybenzamide disappearance time course from rat plasma in vivowas analyzed by a two-compartment model assuming a Michaelis-Menten type elimination process. Ethoxybenazmide oxidation in vitrowas measured by the appearance rate of salicylamide in rat liver microsomal suspension. Parameters obtained were V_max=3.46 and 3.77 moles/min/kg body weight and K_m=0.378 and 0.192mM, in vitroand in vivo,respectively.