Exam 2 - Controlled Drug Delivery Flashcards
(29 cards)
Describe temporal dosing & give examples
dosing over time
- sustained release: delayed, extended
- pulsatile release
Describe spatial dosing & give examples
looking for a particular directed targeting drug delivery (ex. nuclear pharmaceuticals, goal for local delivery)
- systemic
- local
- targeted
Give examples of a drugs that used a diffusion-reservoir system
ocusert
Give examples of a diffusion-controlled system
reservoir devices
matrix devices
Define diffusion-controlled systems
drug diffusion through the polymer network is the rate-limiting step
Explain the mechanism of matrix (monolithic) systems
- drug and matrix former are not physically separated
- drug release depends on the device geometry
- larger concentration of drugs initially → slower concentration of drugs over time
Describe when a matrix (monolithic) system should NOT be used as the drug release system
NOT the most effective mechanism to release a drug if the drug does not take a long time to get into the therapeutic window and is narrow to maintain
List potential advantages of controlled drug delivery
- maintain optimum drug concentration
- improve efficiency of treatment with less amount of drug
- minimize side effects
- less frequent administration (ex: concerta)
- increase patient convenience and compliance with dosing regimen (adherence)
List disadvantages of controlled drug delivery
- relatively high production costs
- leakage of drug mass (dose dumping) → DO NOT CHEW
- difficult to stop drug release
- biocompatibility of the delivery system? (once swallowed, you cannot stop drug)
- necessity of surgical operation
Describe the release mechanism of reservoir devices (diffusion-controlled release systems)
the drug is released at a constant rate over time (when a drug is passing through that membrane, you get a constant drug release)
Describe the release mechanism of matrix devices (diffusion-controlled release systems)
the membrane thickness is essentially changing over time (how the drug has to diffuse through the system will increase because the drug at the surface does not have to diffuse nearly as far as the drug further into the matrix)
List types of dissolution-controlled release systems
encapsulated
matrix
Describe encapsulated dissolution-controlled release systems
- when the drug dissolves, your body immediate releases the drug
- you either get FULL drug release or NO drug release
- the thickness of the membrane determines how quickly the drug will be released
Describe matrix dissolution-controlled release systems
- aka erodible drug system (as the matrix erodes, it releases drug under that particular mechanism)
- the rate controlling membrane itself or the matrix system will actually dissolve
- the surface area and the thickness of dissolution layer DOES change, unlike other systems
Describe full drug release in encapsulated dissolution-controlled release systems
as that matrix slowly dissolves and breaks apart, the polymer membrane dissolves
Explain how the membrane thickness of a encapsulated dissolution-controlled systems
thin membrane: quick release
thick membrane: slow release
List types of osmotic controlled-release systems
- one chamber device
- two chamber device
- reverse osmosis
- film coating
osmotic systems are independent of the pH in the system (regardless where in the body)
Describe osmotic controlled-release systems
allowing water to pass thru the membrane. as water passes thru the membrane, it forces the drug out of a compartment
Describe one-chamber osmotic controlled-release systems
easier to make
semi-permeable membrane that allows only water to pass through
you start with an initial concentration of drug that will slowly decrease overtime as water goes in, and overtime the drug will be pushed out (diluted drug)
Describe advantages of two-chamber osmotic controlled-release systems
water is going thru the system at a constant rate
the drug is not diluted by water, drug is also going thru system at a constant rate
Describe disadvantages of two-chamber osmotic controlled-release systems
more complex to make (making it more expensive)
Describe the reverse osmosis osmotic controlled-release system
by concentrating all the ions, you force all the pure water out of the system
Describe film coating osmotic controlled-release system
- permeable for water
- not permeable for drugs or excipients
- rigid: resist the hydrostatic pressure → push out the drug
Give a simple description of erosion-controlled release systems
when drug is dissolved, drug is released
