DANGGUI (ANGELICA-SINENSIS) AFFECTS THE PHARMACODYNAMICS BUT NOT THE PHARMACOKINETICS OF WARFARIN IN RABBITS

Danggui is a popular traditional Chinese medicinal (TCM) herb which is easily obtained by the public. The effects of Danggui on the pharmaco kinetics and pharmacodynamics of warfarin were studied in rabbits. Sin gle subcutaneous doses (2 mg/kg) of warfarin were administered to 6 ra bbits with or without 3 days treatment with oral Danggui extracts (2 g /kg twice daily). Plasma warfarin concentrations were measured by high performance liquid chromatography (HPLC) for 72 h after each of the t wo warfarin doses. The prothrombin time (PT) was measured daily for 3 days both during the Danggui treatment period and after warfarin doses . Danggui treatment did not affect PT on its own, but significantly lo wered PT values 3 days after co-treatment with single dose warfarin. N o significant variations in the single dose pharmacokinetic parameters of warfarin were observed after Danggui treatment. A separate group o f 6 rabbits were given daily subcutaneous doses of warfarin (0.6 mg/kg ) to achieve steady state level, followed by 3 day treatment with oral Danggui extract (2 g/kg twice daily). The slight increase in PT was n ot significant and two rabbits died after day 7 of the treatment perio d. However, there was no significant difference in steady state concen trations of warfarin after the Danggui treatment. Results indicate tha t precautionary advice should be given to patients who self-medicate w ith Danggui or other TCM products while on chronic treatment with warf arin.