[Studies on the pharmacokinetics of hexobendine in rats. I. Distribution following i.v. administration (author's transl)].

The distribution of 14C-labelled N,N'-dimethyl-N,N'-bis-[3-(3',4',5'-trimethoxy-benzoxy)-propyl]-ethylenediamine-hydrochloride (hexobendine, Ustimon, Reoxyl) in the organs of rats was studied after i.v. injections of 0.5 mg/kg. Up to the 81st min 70-90 percent of the 14C-activity in the lung, heart, skeletal muscle, spleen and brain were formed by unchanged hexobendine, identified by thin-layer chromatography in tissue extracts. In the kidneys and erythrocytes less than 70 percent, in serum and liver less than 50 percent of the measured radioactivity consisted of hexobendine. The serum concentration of hexobendine was 0.1 mug/ml 3 min after administration. This concentration declined with a half-life of 7 min distribution and a half-life of 45 min for elimination. In certain organs the hexobendine concentration rose above the serum level: After 3 min the tissue/serum ratio in the lung was 69, in the kidneys 20, in the heart 7, in the spleen 5, in the liver and skeletal muscle 4, in the erythrocytes 1.2 and in the brain 0.7. The time-dependent decrease in hexobendine concentrations in the various organs was only slightly slower than that in the serum. Only 1 percent of the infected 14C could be detected in the analysed material 12 h after hexobendine administration.