Patches Flashcards
What elements must be considered when developing a patch?
Site of action
Bio-activity and physiochemical properties
Formulation excipients and adhesion
Delivery system
Skin structure
How does percutaneous absorption work?
Drug diffusion, dissolution on surface –> Partition –> diffusion into SC –> partition –> diffusion into epidermis –> partition –> diffusion into dermis –> pentration into blood vessels –> transport to target organs
What is the objective of using dermal therapeutic systems?
maximize drug delivery into stratum corneum, upper epidermis, or dermis; minimizing systemic absorption
Pros of DTS’?
More uiform delivery @ site of application
Longer duration
Substantivity
Deeper penetration
Reduced SE’s
What skin characteristics are needed for a EMLA mixture of local anesthetics?
normal, unbroken
What are some key characteristics of occlusive dressings as DTS’?
air and water tight dressing
Made with waxy coating usually as seal
used to enhance penetration of topically applied medications
hydro-active dressing
Biopatch characteristics?
hydrophilic polyurethane foam/sponge containing broad spectrum antimicrobe agent
Indicated for reducing catheter related blood stream infections
Absorbs ~8x wt in percutaneous fluid
Anti-microbe agent used in biopatch?
Chlorhexidine gluconate
Describe TCCDs.
Band-aid like patch
Contains aqueous media and binding resevoir for prevention of back diffusion of analyte into the skin
Aqueous vehicle creates a conduit between skin and patch fir passive diffusion
molecules in epidermal interstitial fluid migrate across stratum corneum into binding matrix
Drugs can accumulate in TCCDs
correlation between amount collected and drug level in body
What are TCCDs used for?
Compliance issues
PResence of drugs of abuse
Toxic chemicals in workplace
monitoring
Advantages of Non-invasive diagnostic patches?
Increased window of detection
Acts as a detterent to drug abuse
Detects parent drug and drug metabolites
variable removal date
quick application and removal
no urine collections
no sample substitution
no sample dilution
Screens for the hard drugs + weed
What are CFIS(cystic fibrosis indcator system); used for? How do they work?
Detect high amounts of Na and Cl in sweat; pts w/ cystic fibrosis have higher concentrations in sweat
small circular patch that collects sweat and chloride, patch is a chloride complexing chemical and produces a colour change when chloride [ ] are above 45mM
What is a limitation of rtCGM systems (BG monitoring devices not dexcom)
Must be manually calibrated to BG levels 2 x per day
WHat are the differences between Dexcom and Libre devices?
Dexcom has continuous monitoring
low alert<3.1
can share readings
can integrate with slim insulin pumps
2 main uses of DTS’?
Diagnostic and therapeutic application
What is the goal of therpeutic DTS formulation?
epidermal and dermal drug absroption
WHat is the goal of diagnostic DTS formulaiton?
interfacing with dermis
What is the objective of Trandermal delivery systems?
Delivery of maintenance of therapeutic levles of drug in systemic circulation over a long period of time
What are the major limitations w/ transdermal systems?
stratum corneum( rate-limiting barrier), metabolically active layers of skin can biotransform durgs but this is lower than the gut/liver
What are advantages of Transdermal delivery systems?
avoids GI/ absoprtion issues
Alterantive to oral therapy
avoids first pass
multi-day therapy can be achieved w/ 1 application
extemds activity of drugs with short T1/2
easy to terminate drug effect
smooth plasma concentrations of drugs without significant fluctuations for long periods
ease of self admin and improved pt compliance
What are the limitations of transdermal delivery systems?
Can’t use drugs that sensitize the skin
Only potent drugs are suitable; small doses delivered therfore need potent drug
highly dependant on pt factors
very few drugs can be delivered at a viable rate using this route of admin b/c of low permeability
Inter and Intra individual variability:
- regional skin site
- skin age
- changes in peripheral circulation
What would you need to tell a pt on how to apply a TDS?
Clean skin where patch as being applied (can affect adhesion)
Don’t use a patch that has been cut or torn
Make sure patch is smooth when applied w/ no bumps (loose fitting can affect drug penetration)
Do not shave hair, can trim it b/c increases chacnes of irritation and broken skin can affect drug exposure
Do not use a heat pad when patch is applied (on area w/ patch)
Always remove old pach before applying new patch
Dispose of old patch by folding in half w/ sticky sides together to avoid touching drug resevoir
Good drugs for TDS have what characteristics?
High potency
Low molecular wt
lipophilic
short T1/2
low melting point
high skin permeability
non-irritating
non-sensitizing
low oral F
low therapeutic index
What are the different types of TDS’s?
Resevoir type
Matrix Type
SIngle layer DIA (drug in adhesive)
Multilaminate DIA
Dot matrix
