Tumor chronobiology

Traditionally, drug delivery has meant getting a simple chemical absorbed p redictably from the gut or from the site of injection. A second-generation drug delivery goal has been the perfection of continuous constant rate (zer o-order) delivery of simple xenobiotic molecules or common hormones. Living organisms are not 'zero-order' in their requirement for or response to dru gs. They are predictable resonating dynamic systems, which require differen t amounts of drug at predictably different times within the circadian cycle in order to maximize desired and minimize undesired drug effects. (C) 2001 Elsevier Science B.V. All rights reserved.