“…Under comparable conditions in the absence of plasma, IV-VI hydrolyzed slowly to phenytoin; however, no attempts were made at this stage to unambiguously discriminate as to whether the acceleration in the cleavage rates in the presence of plasma was truly enzymatic in nature. Overall, the cleavage of the esters was slowest in dog plasma, consistent with findings of low overall esterase activity in various dog tissues relative to other animal species (37)(38)(39). The differences in the relative cleavage rates indicate that the spectrum of esterases present in plasma varies between the animal species.…”