ABSTRACT
Although the idea of drug targeting to a specific site in the body was first introduced
almost a century ago by Paul Ehrlich (1), the field has emerged as an important area of
research only in the past 40 years or so. The advent of recombinant deoxyribonucleic acid
(DNA) technology and progress in biochemical pharmacology and molecular biology
have not only provided a clearer elucidation of pathogenesis of many diseases and
identification of various types of surface cell receptors but also enabled the production of
several new classes of highly potent protein and peptide drugs (e.g., homo-and
heterologous peptidergic mediators and sequence-specific oligonucleotides) (2). For these
new drugs, and for some conventional drugs (e.g., antineoplastic agents) that have narrow
therapeutic windows and require localization to a particular site in the body, it is essential
that they be delivered to their target sites intact, in adequate concentrations, and in an
efficient, safe, convenient, and cost-effective manner. Most drug therapies currently
available provide little, if any, target specificity. The selective delivery of drugs to their
pharmacological receptors should not only increase the therapeutic effectiveness but also
limit side effects and increase safety.
