title: Stereoselective disposition of RS-tocainide in man.
abstract: The disposition of RS-tocainide in three healthy volunteers has been studied after oral administration of a pseudoracemic mixture containing S(+) [3H] tocainide as a radioactive tracer together with a therapeutic dose of the racemate. Analytical methods based on HPLC have been developed to measure S(+) and R(-) tocainide in urine samples. Selected ion detection has been used for quantification of a tocainide conjugate. The radioactive dose was efficiently absorbed and mainly cleared via the kidneys. The elimination half-life of RS-tocainide was found to be 14.3 hours. The elimination half-lives of the two stereoisomers of tocainide differed significantly, i.e. R(-) tocainide 10 hours, and S(+) tocainide 16.7 hours. The observed t1/2 for the tocainide conjugate of 10.3 hours was close to that of R(-) tocainide, indicating that the metabolite was preferably formed from the R(-) stereoisomer of tocainide. Of the given dose, between 45 and 70% can be accounted for.
mesh_terms: D000328:Adult; D001682:Biological Availability; D002853:Chromatography, Liquid; D006207:Half-Life; D006801:Humans; D008012:Lidocaine / Q000031:analogs & derivatives* / Q000378:metabolism / Q000652:urine; D008297:Male; D008657:Metabolic Clearance Rate; D013237:Stereoisomerism; D016677:Tocainide
chemical_list: D016677:Tocainide; D008012:Lidocaine