Wide variety of polymeric biomaterials are components of the various formulations and devices that are routinely used for delivering drugs to the body this video reviews the current state-of-the-art drug delivery systems that release drugs in a controlled manner when a drug is released the blood plasma level rapidly rises followed by an exponential decay as the drug
Is metabolized and/or eliminated from the body the figure shows drug concentrations above which the drug produces undesirable side effects below which the drug is not therapeutically effective the difference between these two levels is known as the therapeutic index one can minister safe doses at periodic intervals in order to maintain a desired drug concentration
Level however this is inconvenient and patient compliance is often poor for these reasons there has been a great interest in developing controlled release formulations and devices that can maintain a desired blood plasma level for long periods of time without reaching a toxic level or dropping below the minimum effective level these drug delivery systems are
Often called the zeroth order systems since they release drug at a constant rate controlled-release polymeric systems can be classified according to the mechanism that controls the release of the therapeutic agent for examples of these systems are diffusion control water penetration controlled chemically controlled and responsive the diffusion controlled drug
Delivery system is used in drug eluting stents and transdermal patches water penetration controlled drug delivery systems are used in osmotic devices chemically controlled drug delivery systems are used in biodegradable reservoir systems responsive drug delivery systems are used in mechanical pumps and magnetic drug release systems there are two fundamentally
Different devices where the rate of drug release is controlled by drug diffusion these are membrane controlled devices and monolithic devices in membrane controlled reservoir devices the active agent is contained in a reservoir which is surrounded by a thin polymer membrane released to the surrounding environment occurs by diffusion through the rate controlling
Membrane this system is called a reservoir device in a monolithic device the therapeutic agent is uniformly dispersed or dissolved in a polymer matrix its release is controlled by the diffusion from the matrix in this type of delivery device drug release rate is controlled by the rate of water diffusion into the device two general types of drug delivery systems
Are in use osmotic and swelling controlled systems in an aqueous environment water is automatically drawn across the cellulose acetate membrane and the resultant pressure on the rubber reservoir but forces the agent out of the orifice because the driving force is osmotic transport of water across the cellulose acetate membrane rate of release of the agent from the
Device is independent of the surrounding environment however this device works best only with water soluble drugs that act as the osmotic agent to be useful with water insoluble drugs a different version known as the push-pull oros has been developed in this device two compartments are separated by a flexible partition the top compartment contains the drug and
Has a delivery orifice the bottom push compartment contains a solid automatic driving agent such as a water swelling or dissolving polymer a semipermeable membrane surrounds both compartments and regulates water influx into each separately the push compartment is designed to deliver all of the drug out of the device each of the previously described systems are
Based on polymers that do not change the chemical structure beyond what occurs during swelling however a great deal of attention in research effort is being concentrated on biodegradable polymers these materials degrade within the body as a result of natural biological processes eliminating the need to remove a drug delivery system after release of the active
Agent has been completed degradation may take place through bulk hydrolysis in which the polymer degrades in a fairly uniform manner throughout the major for some degradable polymers most notably the pollyanna hydrides and the poly ortho esters the degradation occurs only at the surface of the polymer resulting in a release rate that is proportional to the
Surface area of the drug delivery system dr. robert langer of the massachusetts institute of technology had this to say polymers control these polymers they are permitting new treatments for all kinds of cancer various mental health diseases like schizophrenia and heart disease many many others so let me take brain cancer as an example what we did there is we
Created a polymer and it’s a very special kind of polymer plastic that just dissolves layer by layer and so it doesn’t can’t dump the drug out and also what’s good about it is by changing the chemistry we can actually make the polymer last anywhere from the day to three years or any time in between and what happens now in this treatment is like the neurosurgeon
Would operate on the patient because they’re going to do that anyhow and then they take out as much of the tumor as they can but before they close the patient up what they do is they put these little wafers in here’s this is an example of one of the wafers and usually they put seven or eight in right at the site where they operated and then the idea is the wafer
Keeps releasing the drug over say a month or two in the meantime the wafer dissolves completely so it’s not in the brain and the idea is that wafer will deliver the drug locally right to the tumor killing it but also it doesn’t get to the rest of the body where could cause a lot of side effects so people are taking our developing advanced delivery systems and
We’re working on a lot of these in almost every year the body so some are implanted some are rejected some of you can swallow some are put in as patches some are taken as aerosols into the lung some so there’s all all kinds of different ones existence it’s very exciting something like now i think over 100 million people use use these different kinds of advanced
Drug delivery medications around the world so it’s really gotten into a very very growing field of affection responsive delivery systems were developed to be environmentally sensitive and respond to the presence of specific stimuli the external stimuli can be temperature ph ionic strength ultrasonic sound electric current or others like it there are three ways
That smart gel formulations may be stimulated to release bioactive agents thermally induced collapse which is relevant to skin or mucosal drug delivery ph induced swelling which is relevant to oral drug delivery where the swelling is induced by the increase in ph and going from the gastric to enteric regions soul to gel formation which is relevant to injectable
Or topical formulations of a try block copolymer solution that are thermally gel to body temperature for in vivo uses the block copolymer is designed to be degradable the polymeric drug delivery systems discussed in this video offer a number of advantages over the conventional forms of drug administration thus it is no surprise that many of these devices have
Seen great commercialization efforts the success of these efforts show positive signs for the future of biopolymer development you you
Transcribed from video
Polymeric Drug Delivery Systems – Biomaterials – UND Engineering By kookapalooza