Ak. Sohlenius-sternbeck et al., Metabolism of sameridine to monocarboxylated products by hepatocytes isolated from the male rat, DRUG META D, 28(6), 2000, pp. 695-700
The metabolism of sameridine (LPB) (an amide-type local anesthetic-analgesi
c agent with a hexyl side chain) to carboxylic acid derivatives by isolated
male rat hepatocytes was studied using gradient reversed-phase HPLC and ma
ss spectrometry. Incubation of sameridine with hepatocytes resulted in the
formation of numerous different metabolites. Two carboxylic acids, i.e., th
e C-6 and C-4 carboxylated derivatives of sameridine (LPB-6'-oic acid and L
PB-4'-oic acid), were found to be produced from the intermediate omega-hydr
oxy metabolite (6'-hydroxy-LPB). Shortening of the alkyl chain in LPB-6'-oi
c acid by two carbon atoms resulted in LPB-4'-oic acid. However, incubation
of rat hepatocytes with 5'-hydroxy-LPB [the (omega-1)-hydroxy derivative o
f sameridine] did not give rise to any carboxylated derivative. Addition of
SKF525A inhibited the metabolism of sameridine by rat hepatocytes, indicat
ing that the initial step is catalyzed by cytochrome P450. Furthermore, the
metabolism of sameridine to LPB-4'-oic acid was enhanced in hepatocytes is
olated from rats treated with clofibrate, an up-regulator of peroxisomal fa
tty acid beta-oxidation and of microsomal cytochrome P450 4A. L-Carnitine (
which increases the rate of mitochondrial fatty acid beta-oxidation) had no
effect on the level of LPB-4'-oic acid produced by isolated rat hepatocyte
s. The metabolism of 6'-hydroxy-LPB to LPB-6'-oic acid was inhibited almost
completely by 4-methylpyrazole, an inhibitor of alcohol dehydrogenase. Con
sidered together, our findings suggest that cytochrome P450 4A, cytosolic d
ehydrogenases, and the enzymes involved in peroxisomal fatty acid beta-oxid
ation catalyze the metabolism of sameridine to LPB-4'-oic acid.