Pharmacokinetics is the study of the kinetics of drug absorption, distribution and elimination.
After oral drug administration:
- The drug is absorbed from the site of administration to the systemic circulation.
- The drug is distributed to all parts of the body.
- The drug is eliminated from the body by metabolism and/or excretion.
Notice that intravenous drug administration introduces the drug directly into the systemic circulation, and the drug undergoes distribution and elimination only.
Each process (absorption, distribution, metabolism, and excretion) is associated with one or more parameters which are dependent on the drug, drug product and the patient. These are the pharmacokinetic parameters and they determine the rate and extent of the different processes.
