9: Transdermal Delivery Systems Flashcards
what is the difference between TDS and topical
TDS get into systemic circulation for widespread effects
topical = local effect only
list 3 advantages of TDS drugs
- avoids deactivation
- noninvasive
- less frequent application
- avoids interactions
- effective for drugs that cause nausea
- patient compliance
- ease of removal
- controlled release property
- easily recognizable in emergency
what are some limitations of TDS
- absorption of drugs from skin may be limited
- dermatitis at site
- lag time
the stratum corneum is made up of _____ ____ cells separated from each other by a _________
protein rich cells
thin layer of intercellular lipids
3 ways a drug can pass through the stratum corneum
- paracellular
- transcellular
- through hair follicles and sweat glands
what is the most important mechanism of percutaneous absorption
diffusion
what are the 3 characteristics that makes the best drug for TDS
low MW and melting point, moderate lipophilicity and excretion
3 parts of a TDS
backing membrane
adhesive layer
release liner
the backing membrane of a TDS must be
occlusive
what can the backing membrane be made of
propylene, polyethylene, and polyolefins
where is the drug contained layer located
between the backing membrane and adhesive layer
what is commonly used for the adhesive layer
polybutyl acrylate
which system is zero order release
- membrane controlled system
- monolithic system
membrane release system
if a membrane controlled patch is used right after manufacturing there will be a ________
if it is expired there may be a _________
lay time
dose dumping
what is the only factor we can change of a TDS for release
concentration of drug in reservor
the rate limiting membrane of membrane controlled systems are made of
polymers that slow down release of drug out of patch
describe a monolithic system
drug is mixed with rate limiting membrane = no specific drug reservoir
- just backing, adhesive with drug, and release liner
why do monolithic systems not have zero order release
because as time goes on, the distance of diffusion increases, and rate lowers
reservoir systems can form _______ release while monolithic systems usually form _____ release delivery systems
controlled release
sustained release
list the locations from best for worst for skin penetration
abdomen >forarm > instep >heel
what are some chemical ways to enhance absorption
extraction of lipids alteration of vehicle/ skin partitioning coefficient disruption of lipid bilayer structure displacement of bound water loosening of horny cells delamination of stratum corneum organic solvents oily structure surfactant propylene glycol other drugs
what are some physical absorption enhancers
iontophoresis
phonophoresis
electroporation
what is iontophoresis
generating a constant but low voltage through 2 electrodes to push drug into skin
how does phonophoresis/ sonophoresis work
forms bubbles inside skin and forms cavities inside lipid structure of stratum corneum = loosens it and drugs get better penetration
