ADME
ADME is the story of a drug's journey through the body, told in four chapters. Think of the drug as a traveller: first it has to get in (Absorption), then it spreads around to different neighbourhoods (Distribution), then the body chemically reworks it (Metabolism), and finally it leaves (Excretion). The acronym A-D-M-E captures those four stages in order.
Each step shapes how much drug actually reaches its target and for how long. Absorption governs how much enters the bloodstream; distribution decides which tissues it reaches; metabolism (mostly in the liver) often converts the drug into water-soluble products; and excretion (mostly via the kidneys) removes it. Together these processes are what pharmacokinetics measures and predicts.
ADME is a useful map, but the chapters overlap rather than run strictly in sequence — a drug is being eliminated even while it is still being absorbed. Some texts add an L for Liberation (release from the dosage form) at the front, giving LADME. The framework describes what the body does to the drug, in contrast to pharmacodynamics, which describes what the drug does to the body.
An oral paracetamol tablet dissolves and is absorbed from the gut, distributes into body water, is metabolised in the liver largely by glucuronidation and sulfation, and the conjugates are excreted in urine — one drug walking through all four ADME steps.
Paracetamol traces all four ADME stages.
Remember the direction: ADME = what the body does to the drug; pharmacodynamics = what the drug does to the body.