Pharmacokinetics--one user's perspective

Rate/duration-specified drug delivery systems have recently begun to appear as pharmaceuticals and as research tools. In both therapeutics and research, their major advantage is prevention of transient peaking of blood or tissue concentrations that are side-effect producing and potentially toxic; these peaks are the rule with conventional drench- or pulse-modes of drug administration via ordinary dosage forms. Each drug's pharmacokinetics provides the basis for specifying the rates at which its controlled delivery dosage forms should function in vivo. That is what pharmacokinetics can do for controlled drug delivery systems. What the availability of controlled drug delivery systems can do for pharmacokinetics is to make it both convenient and economical to study the steady-state pharmacokinetic behavior of a drug during chronic administration--as opposed to the much more complex and costly procedure of studying the transient pharmacokinetic behavior of the drug. Moreover, achieving and maintaining an approximately steady-state simplifies the study of spatial gradients in drug concentration in body fluids and tissues. In this fashion, advances in the technology of dosage forms, and the conversion from their static specification only by quantity to a dynamic specification by rate/duration, are strongly interdependent with both the theory and practice of pharmacokinetics.