To date, a number of clinically important drugs have been identified that interact with commonly-used herbs and thus herb-drug interactions have become a safety concern in the use of herbal medicines. These drugs include (amongst others) warfarin, midazolam, digoxin, amitriptyline, indinavir, cyclosporine, tacrolimus and irinotecan. Importantly, many of these drugs have very narrow therapeutic indices. Most of them are substrates for cytochrome P450s (CYPs) and/or P-glycoprotein (P-gp). Because drug-herb interactions can significantly affect circulating levels of drug and, hence, alter the clinical outcome, the identification of drugs that interact with commonly-used herbal medicines has important implications in drug development. In silico, in vitro, animal and human studies are often used to identify drug interactions with herbs. This book is of high scientific value because it highlights the relevance of mechanisms, models and maladies.