Lidocaine Metabolism in Normal and Phenobarbital-pretreated Dogs

The metabolism of lidocaine was investigated in four dogs before and after pretreatment with phenobarbital. The extraction of lidocaine and production of monaethylglycinexylidide (MEGX) and glycinexylidide (GX) were calculated from gradients across the liver. The lidocaine fraction removed was 25 per cent in the controls and 50 per cent following phenobarbital pretreatment. The principal metabolite found was MEGX. Phenobarbital pretreatment may have increased the rate at which MEGX, formed from lidocaine, is metabolized further. Contrary to results of previous studies, GX was discovered to be an additional metabolite of lidocaine. The formation and excretion of GX were accelerated by phenobarbital pretreatment.