Summary
Highlights
Bob Langer introduces the field of controlled drug delivery, emphasizing its impact on millions of patients. He explains the traditional drug delivery method, where peaks and valleys in drug concentration can lead to toxicity or ineffectiveness, and the importance of patient compliance.
Langer differentiates between sustained release and controlled release formulations. Sustained release systems offer longer duration but still result in fluctuations. Controlled release systems, using polymers or pumps, provide a predetermined release pattern over extended periods, unaffected by environmental conditions.
The lecture touches on targeted drug delivery, using liposomes, microspheres, or carriers to direct drugs to specific cells or locations within the body, enhancing efficacy and reducing side effects.
Langer details the three primary mechanisms of controlled drug release: diffusion, chemical reactions, and solvent action. He explains reservoir and matrix systems in diffusion, highlighting the advantages and disadvantages of each.
The second mechanism is chemical reaction including bioerodible systems, where the polymer dissolves gradually, releasing the drug at a controlled rate. He also discusses pendant chain systems where drugs are chemically linked to a polymer backbone and are released upon cleavage.
Langer explains solvent-activated systems where the solvent (usually water) causes swelling, allowing the drug to escape from the polymer matrix. He introduces osmotic pressure as another mechanism which causes water to be absorbed and cracks to be formed on the polymer allowing for drug release.
Osmotic pumps which rely on water driven mechanical parts to provide extremely precise release rates are also explained. He highlights that these systems are widely used.
The lecture dives into specific applications, starting with ocular delivery for glaucoma treatment and artificial tears. He discusses reservoir systems like the Ocusert and challenges in creating long-lasting artificial tears without blurred vision.
Langer describes controlled release contraceptive systems, including non-erodible implants like Norplant and steroid-releasing intrauterine devices, emphasizing their long-term effectiveness.
The role of local tetracycline delivery in matrix systems for periodontal applications and shows how these systems can quickly be installed by a dental professional.
Anti-cancer drugs incorporated into stents are shown to prevent smooth muscle cell division and block off blood flow. Millions of patients used this delivery system every year.
Other applications like schizophrenia and type 2 diabetes are achieved by delivering certain hormones via injection through degradable PLGA systems.
He introduces transdermal systems, where drugs can be administered through the skin via reservoir diffusion systems. He explains key properties of drugs that are useful transdermal
He touches on methods of enhancement through electric fields, electric operations, and ultrasound to enhance permeation of drugs. He ends by summarizing the importance of drug delivery.