- The design of delivery systems that can provide drugs in a chronopharmacologically desirable pattern necessitates the creation of systems that have the capacity to alter the release process once it has commenced. This can be done with various controllers if a pump is utilized. However, pumps have a number of limitations as a delivery vehicle including cost, size, and possible patient inconvenience. Polymer-based delivery systems can significantly reduce such limitations. However, the development of polymer-based systems that can provide increased release rates when required is still at an experimental stage. In this paper, we discuss three approaches we have studied to provide pulsatile release. These are (1) magnetically controlled polymer systems,(2) ultrasonically controlled polymer systems, and (3) enzymatically controlled polymer systems.