Pharmacodynamic and pharmacokinetic interactions between herbs and western drugs

In recent years, the combined use of Herbal medicines and Western drugs has been increasing. Though certain problems may occur when both types of medicines are taken together, they have not been adequately analyzed. It was reported that anticoagulation was enhanced in addition to bleeding when patients took long-term warfarin therapy in combination with Salvia miltiorrhiza (danshen), and laxative herbs accelerate intestinal transit and interfere with the absorption. Herbal constituents, curcumin, ginsenosides, piperine, catechins and silymarin were found to be inhibitors of P-glycoprotein. St John’s wort induces the intestinal expression of P-glycoprotein. Anthraquinone, quercetin and coumarins were found to be a potent inhibitor of P-450. Glycyrrhizin or liquorice extracts, Garlic and St John’s wort are a potent inducer of CYP3A4. This review provides a critical overview of interactions between herbal medicines and other drugs. Hence, it is necessary to study the pharmacodynamic and pharmacokinetic interactions of many herbal medicines between western drugs