title: The fate of 14C-carbendazim in rat.
abstract: The disappearance of 14C-carbendazim in rat (i.v. 12 mg/kg) followed the kinetics of a two-compartment open-system model. Half-lives of the alpha-phase were 0.1 h (blood), 0.16 h (liver), 0.25 h (kidney), and of the beta-phase: 2.15 h, 6.15 h, respectively. Two metabolites: methyl 5-hydroxy-2-benzimidazolecarbamate (5-HBC) and 2-aminobenzimidazole (2-AB) were formed very rapidly. Their peak concentrations in liver and kidney were 15 min after i.v. injection. Unchanged carbendazim was found in highest concentrations in blood. 5-HBC prevails in organs. 2-AB was present only in minor amounts. The extent of bioavailability in orally administered 14C-carbendazim (12 mg/kg) was about 85%. The disposition of radioactivity in subcellular fractions was not uniform, its highest concentration was in cytosol, the lowest in microsomes. The elimination of 14C-carbendazim in urine is biphasic. Half-lives of the alpha-phase were 1.4 h (i.v.) and 2.5 h (oral), and of the beta-phase 11.2 h and 12.1 h, respectively. Irrespective of the route of administration, 95% of the radioactivity in urine was composed of 5-HBC. The concentration of unchanged carbendazim in blood and of 5-HBC in urine may be of diagnostic value in acute poisoning with carbendazim.
mesh_terms: D000284:Administration, Oral; D000818:Animals; D001562:Benzimidazoles / Q000378:metabolism*; D001711:Biotransformation; D001826:Body Fluids / Q000378:metabolism; D002219:Carbamates; D007275:Injections, Intravenous; D007408:Intestinal Absorption; D008297:Male; D008862:Microsomes, Liver / Q000378:metabolism; D051381:Rats; D013997:Time Factors; D014018:Tissue Distribution
chemical_list: D001562:Benzimidazoles; D002219:Carbamates; C006698:carbendazim