Potential Interactions Between Alternative Therapies and Warfarin

Amy M. Heck, Beth A. Dewitt, and Anita L. Lukes


Am J Health Syst Pharm. 2000;57(13) 

In This Article

Limitations of the Literature

Several limitations exist for health care professionals attempting to use these data to make clinical decisions. Nearly all available information on potential drug interactions between warfarin and herbal products is based on in vitro data, animal studies, or individual case reports. Definitive cause-and-effect relationships have not been proven. The findings to date may be confounded by several patient- specific variables, including the presence of other concomitant medications, diseases, and lifestyle factors. Information from in vitro or animal studies may not always predict responses in humans. In addition, the available reports provide only limited information about the onset or severity of the potential interactions, which further limits the development of sound recommendations for managing patients. These problems are further complicated by the lack of information about the safety and therapeutic efficacy of most herbal products and the lack of regulations governing the purity and potency of herbal products during manufacturing. Because the pharmacokinetic and pharmacodynamic properties of most herbal products are poorly understood, potential interactions with warfarin cannot be predicted with any confidence. Therefore, the list presented in this review cannot be considered all-inclusive, and continued vigilance and reporting of potential interactions are needed.


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