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22 Cards in this Set
- Front
- Back
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Types of polymeric implants
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-Diffusion controlled drug release
-Stimuli-sensitive drug release -Biodegradation-controlled drug release -Sol-gel polymers for drug release |
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Characteristics of polymeric implants
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-Controlled drug release over a long time frame for improved drug therapy
-Decrease toxicity -Minimize number of injections. -Increase patient compliance. -Safety? Infection? -Is the polymer biocompatible? -Is it biodegradable? -Are the by-products of biodegradation toxic? -Is it expensive? -Potent drugs! |
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Diffusion controlled drug release (matrix system)
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Polymer and active agent have been mixed to form a homogeneous system
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Factors affecting diffusion controlled drug release (matrix system)
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Drug release depends on the content of drug in the polymer matrix, its size, and structure of the polymer.
-Rate decreases as more drug is released because it has farther to travel. |
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Design of diffusion controlled drug release
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-In this design, a reservoir is surrounded by a rate-controlling membrane which is the only structure limiting the release of drug
-Follows Fick's First Law |
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Cons to diffusion controlled drug release devices
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-non-biodegradable
-invasive: requires minor surgical procedure |
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Stimuli-sensitive drug release
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Drug release in response to an external signal such as:
-pH -temperatures -chemicals |
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Hydrogels
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-Cross-linked hydrophilic polymers that swell in water (absorb water).
-The swelling of the hydrogel can be triggered by signals so that it can either shrink or swell upon a change in signals |
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Self-regulating insulin delivery
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Molecular gates made up of glucose oxidase and polymers with a weak acid side chains
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Biodegradable polymers
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Drug release controlled by polymer degradation
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Design of biodegradable polymers
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-Most biodegradable polymers are designed to degrade as a result of hydrolysis.
-Degradation can occur by bulk hydrolysis in which polymer degrades in a fairly uniform manner throughout the matrix. |
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Biodegradable polymers: poly-anhydrides
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Degrade only at the surfaces, resulting in a release rate proportional to the surface area
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Type I biodegradable polymers
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-------------x------------x------------
to ------------- -------------- ------------ (x = labile backbone bonds) |
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Type II biodegradable polymers
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----------- to -------------
A A B B A is hydrophobic sidegroup B is hydrophilic sidegroup |
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Type III biodegradable polymers
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Have cross links that can be broken, leading to polmer degradation
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Gliadel wafers
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Gliadel® wafers delivers BCBU directly to the site of the recurrent brain tumor.
Wafers dissolve over two to three weeks to kill brain cells left behind in surgery. |
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Give an example of a vaccine that is delivered by biodegradable microspheres
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Single dose diphtheria-pertussis, and tetanus (DPT) vaccine
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Goals of thermo-sensitive biodegradable gels for protein delivery
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Goal: load drug in solution state (sol), inject sol, and release drug in gel state.
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Types of polymers for protein delivery
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-Polyethylene glycol is a common polymer used for drug formulation.
-Poly(lactic acid) is a biodegradable polymer used for drug delivery. -The thermo-sensitive polymer is an AB or an ABA block copolymer |
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PEG-b-PLA-b-PEG polymer
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-A PEG-b-PLA-b-PEG is a solution at 25°C and forms a gel at body temperature
-Simple and requires no organic solvent. -Acts as a sustained release matrix. -Administration of the solution can be carried out by simple SC injection after reconstitution of the polymer with saline |
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Chemoembolization for liver tumors
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Since liver tumors get most of their blood from the hepatic artery, the chemo is injected through the hepatic artery to treat the tumor and hopefully spare the healthy tissue of the liver.
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Atridox
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-PLA is dissolved in a safe organic solvent, N-methyl-2-pyrrolidone, and it can be combined with a drug, such as doxycycline
-solution is placed into accessible tissue sites through a cannula, and PLA precipitates to form a solid implant for local drug release. -PLA degrades over several days, releasing drug |
