Significant pharmacokinetic/pharmacodynamic interactions between various herbal products and warfarin have recently been reported. The aim of this study was to determine whether concomitant treatment of rats with Kan Jang (a standardized fixed combination of extracts from Andrographis paniculata and Eleutherococcus senticosus) and warfarin would lead to an alteration in the pharmacological effects of warfarin. Each day for 5 days a group of animals was treated orally with an aqueous solution of Kan Jang at a dose of 17 mg/kg of the active principle andrographolide (a daily dose some 17-fold higher than that recommended for humans): the control group received similar treatment with appropriate volumes of water only. Sixty minutes after the final daily administration of Kan Jang or water, an aqueous solution of warfarin (0.2 mg/ml) was given to each animal at a dose of 2 mg/kg. From each group, 6 animals were sacrificed at 0, 2, 4, 6, 8, 12, 24, 30 and 48 h after warfarin administration and blood samples taken. The concentration of warfarin in blood plasma was measured by capillary electrophoresis using 50 mM borate buffer (pH 9.3) as mobile phase with simultaneous detection of warfarin at 208.1 and 307.5 nm. Prothrombin time in blood plasma was measured using thromboplastin reagent. The concomitant application of Kan Jang and warfarin did not produce significant effects on the pharmacokinetics of warfarin, and practically no effect on its pharmacodynamics.