The introduction of new and potent drugs and the scientific advancement of effective and safer usage of drugs aimed at the optimization of pharmacotherapy have stimulated the "science of input" and a new concept of drug delivery has emerged. Drug delivery systems (DDS) are designed and formulated on the basis of sound and multidisciplinary information although some of them still cannot be defined at present. New concepts of drug delivery have so far been developed in two fields, namely (1) DDS with controlled-release characteristics and (2) drug targeting. Introduction of controlled release DDS has already given some impetus to medical practice, although they are still far from an ideal pattern-specific drug delivery. As for drug targeting, targets readily accessible to local administration appear to be promising and various new products are on the market. However, systemic drug targeting is still in the concept stage except for those experimental therapies related to life-threatening diseases. A better understanding of diseases, the introduction of an integrated technical approach including medicinal chemistry, sound safety considerations, and the incorporation of various new concepts should lead to new high-technology DDS. The concept of controlled delivery and targeting and their integration into DDS is indeed a momentous revolution comparable to the discovery of a new class of chemical entities.
