Drugs in the body

Pharmacokinetics covers the processes of how much drug is in the body. It can also be thought of as "what the body does to the drug". In order for a drug to work, it must reach therapeutic concentrations

at the site of action. Unless a drug is directly injected into the systemic circulation, it will usually go through some absorption process. Once in the systemic circulation, the drug is distributed to the tissues, liver, or kidneys. The topics of absorption, volume of distribution, and clearance (which encompasses metabolism and excretion) are discussed at length. These concepts are explored using intravenous bolus, intravenous infusion and oral dosage forms as examples.