• A series of chemical modifications of a drug compound by enzymatic activity that make the substrate (drug) more water soluble to allow its clearance from the body. Drug metabolism occurs in two phases: Phase I (biotransformation) involves oxidation, hydroxylation reduction, and hydrolysis. Phase II (conjugation) involves synthesis and conjugation.
  NCI
  U.S. National Cancer Institute, 2021
• The buildup and breakdown of drugs for utilization by the organism.
  CRISP Thesaurus
  National Institutes of Health, 2006
• The liver is the principal site of drug metabolism (for review, see [1 ]). Although metabolism typically inactivates drugs, some drug metabolites are pharmacologically active--sometimes even more so than the parent compound. An inactive or weakly active substance that has an active metabolite is called a prodrug, especially if designed...
  Merck Manuals
  Merck & Co., Inc., 2025
• The liver is the principal site of drug metabolism. Although metabolism typically inactivates drugs, some drug metabolites are pharmacologically active--sometimes even more so than the parent compound. An inactive or weakly active substance that has an active metabolite is called a prodrug, especially if designed to deliver the active...
  Merck Manuals
  Merck & Co., Inc., 2025