Metabolism of lidocaine in human liver in vitro

We have incubated the local anaesthetic drug lidocaine with microsomes from human adult livers. The metabolites deethylated lidocaine (MEGX) and aromatically hydroxylated lidocaine (3-hydroxylidocaine) were isolated by high performance liquid chromatography and quantitated by the liquid scintillation counting technique. The deethylation rate markedly exceeded the hydroxylation rate also at very low lidocaine concentrations. This pattern differs from that detected earlier with rat liver microsomes where aromatic hydroxylation is significant at low lidocaine concentrations, but it is similar to that in female guinea pig microsomes. These findings show the importance of performing this type of experiments also with human materials.