Simultaneous determination of NK611, a novel water-soluble derivative of etoposide, and its metabolite (DeNK611) in dog plasma by column-switching high performance liquid chromatography.

A simple, selective, reversed phase liquid chromatographic method using a column-switching technique has been developed for the simultaneous determination of a novel derivative of etoposide (NK611) and its O-demethyl metabolite in dog plasma. A good linear response was obtained for both drugs in the range 0.1-12.0 micrograms/mL. The mean recoveries were within 100 +/- 5%. The within- and between-day precisions were within 3.5% and 4.6%, respectively. This method was used in a pharmacokinetic study following intravenous and oral administration of NK611 to beagle dogs.