Book excerpt: Relied upon by dermatologists and medical practitioners internationally for its unparalleled practical focus on adverse effects and cutaneous reactions, this text is the essential quick-reference tool for patient care and drug safety. The reaction data for this new 20th edition is compiled from the companion website, which is updated continuously, and includes prescription and over-the-counter drugs as well as biologics, supplements, and other medical products—with tens of thousands of adverse drug reactions, eruptions, and reaction patterns. The text notes the number of peer-reviewed references for reaction listings, the reported incidence of a reaction, and clinically important and potentially serious interactions between drugs.