药物传输载体 DrugDelivery.ppt

Introduction to Controlled Drug Delivery Corinne Lengsfeld Department of Engineering University of Denver Classical drug delivery For most of the pharmaceutical industries existence, drug delivery induced simple, fast-acting responses via oral or injection delivery routes Problems associated with this approach Reduced potencies because of partial degradation Toxic levels of administration Increase costs associated with excess dosing Compliance issue due to administration pain Why control drug delivery? Goal of more sophisticated drug delivery techniques Deploy to a target site to limit side effects Shepard drugs through specific areas of the body without degradation Maintain a therapeutic drug level for prolonged periods of time Predictable controllable release rates Reduce dosing frequent and increase patient compliance History of Controlled Drug Delivery Wurster technique 1949 Coacervation (liquid encapsulation) 1953 Mircroencapsulation 1960’s 65% of all current drugs use some form of micro-encapsulation Implants 1970’s Transdermal 1980’s Site directed systems 1990’s Entrapment or Encapsulation During the 1970, scientists first began to encapsulate and entrap drugs within polymers Encapsulation involves surrounding drug molecules with a solid polymer shell Entrapment involves the suspension of drug molecules within a polymer matrix. Drug release by diffusion Early encapsulation and entrapment systems released the drug from within the polymer via molecular diffusion When the polymer absorbs water it swells in size Swelling created voids throughout the interior polymer Smaller molecule drugs can escape via the voids at a known rate controlled by molecular diffusion (a function of temperature and drug size) Drug release by erosion Modern delivery systems employ biodegradable polymers When the polymer is exposed to water hydrolysis occurs Hydrolysis degrades the large polymers into smaller biocompatible compounds Bulk erosion