Interaction between warfarin and danshen (Salvia miltiorrhiza)

OBJECTIVE: TO discuss the potential for an adverse interaction between the Chinese herb danshen, the dry root and rhizome of Salvia miltiorrhiza Bge, and warfarin. DATA SOURCES: A MEDLINE search was performed (from January 1966 through October 2000) using the key words danshen and Salvia miltiorrhiza. Ail articles written in English or with an English extract were considered for review. STUDY SELECTION AND DATA EXTRACTION: Ail studies of antithrombotic effects of danshen or interaction between danshen and warfarin were evaluated. Previous case reports of an adverse interaction between danshen and warfarin were reviewed. DATA SYNTHESIS: Danshen is commonly used in mainland China for the treatment of atherosclerosis-related disorders such as cardiovascular and cerebrovascular diseases. Danshen can affect hemostasis in several ways, including inhibition of platelet aggregation, interference with the extrinsic blood coagulation, antithrombin III-like activity, and promotion of fibrinolytic activity. Single-dose and steady-state studies in rats indicated that danshen increased the absorption rate constants, AUCs, maximum concentrations, and elimination half-lives, but decreased the clearances and apparent volume of distribution of both R- and S-warfarin. Consequently, the anticoagulant response to warfarin was exaggerated. Three cases have previously been published reporting gross overanticoagulation and bleeding complications when patients receiving chronic warfarin therapy also took danshen. CONCLUSIONS: Because of both pharmacokinetic and pharmacodynamic interactions, danshen should be avoided in patients taking warfarin.