ABSTRACT
At a fundamental level, the importance of concentration and elaborating the parameters that govern the concentration and lifetime of a drug in vivo, from its adsorption, accumulation, and elimination, has been the focus of the study of the field of pharmacokinetics and its parent discipline biopharmaceutics. Bioavailability is a term used to indicate both the rate and fraction of an administered drug that reaches the general circulation intact. The preeminent variable governing bioavailability is the mode of administration. As a drug is absorbed and enters the general circulation, its concentration in the blood begins to rise. Experimentally, for ease of analysis a drug’s concentration in blood is measured as its concentration in plasma, i.e., a blood sample is taken, centrifuged to precipitate the red blood cells, and then the supernatant or plasma is analyzed for drug concentration. A special case of noncompetitive inhibition that is sometimes seen in drug metabolism studies, particularly with cytochrome P450-catalyzed reactions, is suicide inhibition.
