Pharmacokinetic Profiles of Anticancer Herbal Medicines in Humans and the Clinical Implications

A number of herbal medicines are increasingly used by cancer patients worldwide, despite the fact that the clinical evidence that supports their use to fight cancer is weak or lacking. Pharmacokinetic studies have been integrated into modern drug development, but they are generally not needed for herbal remedies. To update our knowledge in this field, this paper highlights the pharmacokinetic properties of anticancer herbal medicines and the clinical relevance. To retrieve relevant data, the authors have searched through computer-based literatures by full text search in Medline (via Pubmed), ScienceDirect, Current Contents Connect (ISI), Cochrance Library, CINAHL (EBSCO), CrossRef Search and Embase ((all from inception to May 2011). An extensive literature search indicates that there are limited data on the pharmacokinetic properties of anticancer herbal medicines in humans. There are increasing pharmacokinetic studies of anticancer herbal remedies, but these studies are mainly focused on a small number of herbal medicines including curcumin, ginseng, ginkgo, ginger and milk thistle. For an anticancer herbal medicine, the pharmacological activity is gained when the active agents or the active metabolites reach and sustain proper levels at their sites of action. Both the dose levels and pharmacokinetic processes of active herbal components in the body determine their target-site concentrations and thus the anticancer effect. In this regard, a safe and optimal use of anticancer herbal medicines requires a full understanding of their pharmacokinetic profiles. To optimize the use of anticancer herbal remedies, further studies to explore their pharmacokinetic properties and the relavance to pharmacodynamics and toxicity in humans are certainly warranted.