Pharmacokinetics - commonly abbreviated as PK - covers the processes of "what the body does to the drug". More specifically, PK usually describes in a quantitative way how much drug is in the body. The 'journey' a drug has to travel usually starts with an absorption process, unless a drug is directly injected into the systemic circulation. Once absorped in the systemic circulation, drug distribution takes place, in which the drug in transported to the tissues, liver, or kidneys. The drug does not stay forever in the human body. Instead, drug elimination takes place, meaning that the drug is then either (or both) metabolised or excreted (e.g. in the urine via the kidneys).
The complete drug 'journey' is often abbreviated as ADME (absorption-distribution-metabolism-excretion). The topics of absorption, volume of distribution, and clearance (which encompasses both metabolism and excretion) are discussed at length. These concepts are explored using intravenous bolus, intravenous infusion and oral dosage forms as examples. For all cases and whatever the ADME-process is, one should realise that for a drug to work, it must reach therapeutic concentrations at the site of action.
In pharmacology, what is the difference between excretion and elimination?
Extra info: Elimination is the process in which drug is removed from the body, either by metabolism or by excretion