1-(2-o-Chlorobenzoyl-4-chlorophenyl)-5-glycyl-aminomethyl-3- dimethylcarbamoyl -1H-1,2,4-triazole hydrochloride dihydrate, (450191-S), exhibits pronounced central nervous system (CNS) activities similar to those of
benzodiazepines, but it has only low affinity for
benzodiazepine receptors. However, when
450191-S was administered to rats at a dose of 10 mg/kg, brain extracts markedly inhibited [3H]
diazepam binding to the receptors. Thin-layer chromatography (TLC), high performance liquid chromatography (HPLC), and radioreceptor assay (RRA) were used to isolate three metabolites that could inhibit [3H]
diazepam binding prominently. These were identified by gas chromatography-mass spectrometry (GC/MS) as compounds having the triazolo-
benzodiazepine skeleton. They showed high affinities for
benzodiazepine receptors (Ki = 0.9 to 2.1 nM) and exerted potent pharmacological effects similar to those of
450191-S. In addition, their levels in the brain were sufficient to explain the pharmacological activity of
450191-S, which could not be detected in
tissue extracts 15 min after administration. These results indicate that the pharmacological activity of
450191-S is largely due to the action of active metabolites, although some points remain to be elucidated to fully account for the large attenuation of the side effect (
ataxia) compared with the major effects (anti-
convulsant and
hypnotic). We also determined the brain levels of metabolites following the administration of
450191-S and evaluated the extent to which each active metabolite contributes to the pharmacological activities of this
drug.