Abstract

The cytochrome P450 system is a group of enzymes, found mainly in the liver and gut mucosa, that plays a crucial role in controlling the concentrations of many endogenous substances and drugs.1 The activity of the individual enzymes can vary over time and from person to person in response to diet, medicines or exposure to environmental pollutants. It has been almost 15 years since DTB reviewed the significance of the cytochrome P450 system and its relevance to prescribing (Why bother about cytochrome p450 enzymes?).1 A lot has changed in healthcare over that time, but has our understanding of this important aspect of drug metabolism altered significantly? Here we provide a brief overview of the function of cytochrome P450 enzymes and look at some of the concepts that have become established, or have begun to emerge, since the publication of our previous article.