title: Controlled Drug Delivery: Historical perspective for the next generation.
abstract: The modern day drug delivery technology is only 60years old. During this period numerous drug delivery systems have been developed. The first generation (1950-1980) has been very productive in developing many oral and transdermal controlled release formulations for clinical applications. On the other hand, the second generation (1980-2010) has not been as successful in generating clinical products. This is in large part due to the nature of the problems to overcome. The first generation of drug delivery technologies dealt with physicochemical problems, while the second struggled with biological barriers. Controlled drug delivery systems can be made with controllable physicochemical properties, but they cannot overcome the biological barriers. The third generation (from 2010) drug delivery systems need to overcome both physicochemical and biological barriers. The physicochemical problems stem from poor water solubility of drugs, large molecular weight of peptide and protein drugs, and difficulty of controlling drug release kinetics. The biological barriers to overcome include distribution of drug delivery systems by the body rather than by formulation properties, limiting delivery to a specific target in the body. In addition, the body's reaction to formulations limits their functions in vivo. The prosperous future of drug delivery systems depends on whether new delivery systems can overcome limits set by human physiology, and the development process can be accelerated with new ways of thinking.
authors.affiliation: Purdue University, Departments of Biomedical Engineering and Pharmaceutics, West Lafayette, IN 47907, U.S.A.
authors.forename: Yeon Hee
authors.initials: YH
authors.lastname: Yun
authors.affiliation: Purdue University, Departments of Biomedical Engineering and Pharmaceutics, West Lafayette, IN 47907, U.S.A.
authors.forename: Byung Kook
authors.initials: BK
authors.lastname: Lee
authors.affiliation: Purdue University, Departments of Biomedical Engineering and Pharmaceutics, West Lafayette, IN 47907, U.S.A.. Electronic address: kpark@purdue.edu.
authors.forename: Kinam
authors.initials: K
authors.lastname: Park
mesh_terms: D000818:Animals; D016503:Drug Delivery Systems / Q000266:history* / Q000639:trends; D049673:History, 20th Century; D049674:History, 21st Century; D006801:Humans; D004364:Pharmaceutical Preparations / Q000008:administration & dosage
chemical_list: D004364:Pharmaceutical Preparations
keywords: Biological barriers; Drug delivery; History; Physicochemical barriers