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
What are the characteristics of resevoir TDS’?
Separate drug compartment contains drug solution or suspension in a reservoir space
Contains; drug dissolved in solvent, liquid excipients, penetration enhancer
Drug delivery controled by membrane control
Follows 0 order kinetics usually –> constant rate irrrespective of [ ]
Describe the adhesive of resevoir TDS
mostly a continuous layer on the membrane
Can be in a concetric configuration on the perimeter of the patch as well
What are disadvantages of Resevoir TDS?
Interactions with adhesive and drug or excipient
Vunerable to burst release –> rupture of membrane dueto material defect, wear, inadvertent puncture
2 Examples of Resevoir type TDS?
Androderm
Transderm-Nitro (not Nitro-Dur brand = adhesive type)
What is the major difference between resevoir and matrix?
Matrix the rate is limited by the drug formulation/polymer not a membrane
What are the characteristics of MAtrix TDS?
Drug compartment: contains drug solution or suspension form in matrix, drug containing semisolid disc held in contact w/ skin by adhesive tape
Formulation conatins: drug dissolved in semisolid, penetration enhancer
First Order reaction, rate depends on [ ] of drug in matrix and stratum corneum
Describe adhesive of matrix TDS
Matrix can be adhesive, can also be seprate adhesive layer
What are the disadvantages of Matrix TDS?
total patch surface area can be a lot larger than the actual drug delivery surface
Protective overlay may be mistkaen for the part to be applied to the skin
2 examples of matrix TDS’?
Exelon
Sandoz- Fentanyl patch
What are characteristics of Drug in adhesive TDS’?
Drug compartment: drug dissolved in an adhesive, very thin patch, state-of-the-art, very comfortable, maximum utilization of SA of the patch
Formulation contains: drug dissolved in a pressure sensitive adhesive, adhesive compostion must be customized for each drug
First order kinetics, Rate controlling adhesive and the stratum corneum
Describe the adhesives for DIA’s?Examples?
Examples: PIB, silicone, acrylate
entire surface of patch is adhesive
pressure sensitive
What are disadvantages of DIA’s?
First order kinetics ; drug [ ] falls in adhesive and is difficult to maintain a cosntant drug delviery
How can you over come drug [ ] falls in adhesive and is difficult to maintain a cosntant drug delviery in DIA’s?
Use of multi-laminante DIA nstead of single
Examples of DIA’s?
Estradot
EVRA
Describe dot-matrix TDS (Dot-matrix very little talked about probably not important for test)
Drug compartment: acrylic to hold drug in high [ ], semisolid suspension: microscopic drug in acrylic droplets evenly dispersed in non-compromised silicone adhesive
Formulation contains: drug dissolved in acrylic, adhesive silicone polymer.
How can patches confuse pts?
Many different designs, dosage strengths, frequency of admin differences, shapes, sizes, colours, site of admin differences.
What is Iby eleontophoresis?
The main force used to drive substances across the stratum corneum ; charged particle movement by electrophoresis. Low voltage current enables the diffusion of substances across stratum corneum and can control drug delivery rate using a micropreocessor or by the pt.
How long does a biopatch last for?
7 days
A patient comes in and is frustrated that they have to keep shaving the hair on their arm for their patch. What do you say?
dont shave= can cause broken skin
Which type of patch has 0 order kinetics?
reservoir
Which type of patch has 1st order kinetics?
matrix, DIA
Which type of patch requires an penetration enhancer?
all usually
If a patient wants the thinnest patch possible which do we give?
DIA
Can you interchange between a matrix to DIA or reservoir patch?
Not always= or just no
What adhesive is used for dot matrix?
silicon polymer
Which polymer holds the drug in dot matrix?
acrylic
What are common issues with patches?
not removing old, not removing protective layer
wrong location
TTS DOES NOT mean tuesday thursday saturday LMAO
Pediatric patients require that their patches be cut. What patches are the only option?
matrix or DIA
