What is drug metabolism?

Xenobiotic metabolism is the protective biochemical process by which a living organism enzymatically or nonenzymatically alters a xenobiotic (foreign substance) to a metabolite that is inactive or quickly eliminated. Drug metabolism applies this to pharmaceutical agents. In general, metabolism begins with a lipophilic drug and converts it to a more hydrophilic metabolite to facilitate elimination. Multiple enzymes and paths are possible for a single xenobiotic, so multiple metabolites are common.

Core idea: the body turns fat-loving (lipophilic) drugs into water-loving (hydrophilic) metabolites so the kidneys can flush them out. One drug can take several paths at once, producing several metabolites.

📖 “Xenobiotic metabolism converts a foreign substance to an inactive or quickly eliminated metabolite; drug metabolism turns lipophilic drugs into more hydrophilic metabolites for elimination.”