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Abstract
1. 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 α-phase were 0.1 h (blood), 0.16 h (liver), 0.25h (kidney), and of the β-phase: 2.15h, 6.15h and 6.15h, respectively.
2. 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.
3. 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.
4. The elimination of 14C-carbendazim in urine is biphasic. Half-lives of the α-phase were 1.4h (i.v.) and 2.5h (oral), and of the β-phase 11.2h and 12.1 h, respectively. Irrespective of the route of administration, 95% of the radioactivity in urine was composed of 5-HBC.
5. The concentration of unchanged carbendazim in blood and of 5-HBC in urine may be of diagnostic value in acute poisoning with carbendazim.