Disposition of ethimizol, a nootropic drug, in rats and mice

The pharmacokinetics of ethimizol, a nootropic drug, were studied in rats and mice using [2-14C]-4,5-di(methylcarbamoyl)-1-ethyl-imidazole. Autoradiography in mice injected iv showed a rapid and homogeneous distribution of the label into the tissues, brain included, and its excretion by the urinary pathway. The determination of ethimizol in plasma, organs, and excreta was based on combined extraction and the TLC procedure. In rats, the elimination half-life of ethimizol after iv administration of 10 mg/kg was 25 min, and its distribution volume was 1.4 liters/kg. The tissue/plasma concentration ratio for organs investigated was 1 immediately after iv administration, with a subsequent gradual increase. Based on this, saturable tissue binding of ethimizol in the liver, kidney, and brain was suggested. The drug was almost completely absorbed after administration, yet its systemic availability was only 32%. The brain uptake index of ethimizol was 101% as compared to 3H2O. Ethimizol was eliminated by metabolism. The labeled metabolites were predominantly excreted in the urine.