"Drug metabolism in diseases", now in second edition, provides pharmaceutical scientists and biologists with the needed foundational knowledge required to understand the interplay between diseases and physiological conditions, how they impact drug metabolism and disposition, and its implications in personalized treatment. The book has been expanded with six new chapters, and completely updated with the scientific findings since the first edition published in 2016. The new chapters in the book cover drug metabolism in metabolic syndrome , transplant patients, geriatric patients, the developmental regulation of drug metabolism and disposition, the effect of gut microbiota on xenobiotic and endobiotic metabolism, the regulation of expression of drug-metabolizing enzymes by oncogenic signaling pathways, and drug metabolism in HIV patients. All other chapters in the first edition like drug metabolism in pregnancy, pediatric patients, patients of cardiovascular disease, and kidney diseases were completely updated to include the latest research results and references. "Drug metabolism in diseases" is a comprehensive reference on the mutual effect between drug metabolism and diseases, which has great implications in precision medicine and therapeutic development. Pharmaceutical scientists and drug metabolism researchers in academia and corporate R&D departments will benefit from the expanded coverage provided by expert authors. Research physicians interested in better understand the impact of diseases in drug metabolism will also benefit from the comprehensive overview of the area.