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PHAR224 > Patches > Flashcards

Patches Flashcards

1
Q

What are the two systems for patches?

A

dermal therapeutic systems (DTS)
-local
transdermal therapeutic systems (TTS)
-systemic

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2
Q

What are the elements to be considered when discussing patches?

A

site of action (local & systemic)
bio-activity and physicochemical properties of the drug
formulation excipients and adhesion
delivery system
skin structure

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3
Q

What are the objectives for dermal therapeutic systems?

A

to maximize delivery of drug from formulations into stratum corneum, upper epidermis or dermis, and at the same time minimize further absorption through the skin into the systemic circulation
intended for localized effect

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4
Q

What do dermal therapeutic systems offer?

A

more uniform delivery at site of application
-sustained delivery
longer duration (ability to retain drug in SC longer); substantivity (resistance to wash-off)
deeper penetration
-local anesthetics, anti-inflammatory, analgesics
reduced side effects
-reduces irritation due to lower dose

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5
Q

What are four examples of dermal therapeutic systems?

A

pain-relief: EMLA
occlusive dressings: Actiderm
antimicrobial agents: Biopatch, bandaids
non-invasive diagnostic patches: TCCD, CFIS, Dexcom, Freestyle

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6
Q

What is EMLA?

A

mixture of local anesthetics
-lidocaine 2.5% + prilocaine 2.5%
-skin numbing cream
disc application
-peel and stick patch
-polymer matrix contains the active and the adhesive is located peripherally

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7
Q

What kind of skin can EMLA be used on?

A

normal, unbroken skin
-prevents pain before procedures such as inserting a needle for injections or drawing a blood or before vaccinations

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8
Q

What is Actiderm?

A

hydrocolloid patch
enhances the efficacy of topical steroids
flexible hydro active dressing

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9
Q

Describe occlusive dressings as DTS.

A

air and water-tight dressing which are generally made with a waxy coating to provide a total seal
used to enhance penetration and absorption of topical medications

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10
Q

What is a biopatch?

A

a hydrophilic polyurethane foam/sponge containing a broad spectrum antimicrobial
-chlorhexidine gluconate

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11
Q

What is the indication for a biopatch?

A

reduce catheter-related blood stream infections
-wrapped around percutaneous devices to reduce the risk of infection
-absorbs up to 8x its weight of percutaneous fluid, continuously releases the drug and inhibits bacterial growth for 7d

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12
Q

What are analyte collection patches/transcutaneous chemical collection devices?

A

band-aid like patches containing aqueous media and a binding reservoir to prevent back diffusion of analyte into skin

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13
Q

Describe how TCCDs work.

A

when affixed to skin the aqueous vehicle creates a conduit between the skin and the patch for the passive diffusion of sweat and chemicals
chemical molecules in the epidermal fluid move by passive diffusion across the SC into the binding matrix

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14
Q

Which drugs can accumulate in TCCDs?

A

caffeine
theophylline
cocaine
opiates (heroin, morphine)
amphetamines
ethanol

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15
Q

What are the applications of TCCDs?

A

drug monitoring and compliance
presence of drug of abuse
toxic chemicals in the work place
monitoring the level of medically important endogenous compounds

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16
Q

What are the advantages of non-invasive diagnostic patches?

A

increased window of detection
acts as a deterrent to drug abuse
detects parent drug and metabolites
variable removal date
quick application & removal
no urine collection
no sample substitution
no sample dilution
screens for: marijuana, cocaine, opiates, amphetamines, meth, PCP, ecstasy

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17
Q

What is the cystic fibrosis indicator system?

A

a small circular patch, collects sweat and Cl ions as a screening test for CF
patch has a chloride-complexing chemical, it changes color when Cl is >45mM
screening test, not monitoring test

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18
Q

What is a pathogenic defect of cystic fibrosis?

A

high concentration of Na and Cl in sweat

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19
Q

What kind of glucose monitoring system is the Dexcom?

A

real time glucose monitoring system

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20
Q

What is the limitation of real time continuous glucose monitoring?

A

they require manual calibration to BG levels ~twice per day
-except for the current G6 systems

21
Q

What kind of glucose monitoring system is the Freestyle Libre?

A

intermittent glucose monitoring system
-lancet free

22
Q

What is the difference between Dexcom and Freestyle Libre?

A

Dexcom is real time, Libre is intermittent
-continuous data: Dexcom=yes, Libre=no
-low alert: Dexcom=yes, Libre=no
-remote monitoring: both=yes
-insulin pump compatibility: Dexcom=yes, Libre=no

23
Q

Which sensor is of choice in management of type 1 diabetes in infants and children?

A

Dexcom
-compatible with insulin pumps

24
Q

Provide a brief overview of the conclusions to take away from DTS.

A

used for diagnostic and therapeutic applications
goal of therapeutic formulation=epidermal and dermal drug absorption
goal of diagnostic application=interfacing with dermis
ideal DTS formulation=maximize drug penetration into dermis but minimized systemic absorption
intended for localized action

25
Q

What is the objective of transdermal delivery systems?

A

delivery and maintenance of therapeutic levels of drug in the systemic circulation over a long period of time with the most convenience to the patient

26
Q

What is the major limitation to transdermal drug delivery?

A

stratum corneum (rate-limiting barrier) AND metabolically active layers of the skin have biotransformation capacity (lower than the gut or liver)

27
Q

What are the advantages of transdermal delivery?

A

avoids GI drug absorption difficulties
is an alternative to oral or parenteral administration
avoids first-pass hepatic metabolism
multi-day therapy can be achieved by a single application
extends the activity of drugs with short half-lives
easy to terminate the drug effect
smooth plasma concentration of drugs without significant fluctuations for long periods
ease of self-administration and patient compliance

28
Q

What are the limitations of transdermal delivery systems?

A

expensive
unsuitable for drugs which sensitize the skin/sensitivity of skin for excipients
only potent drugs are suitable candidates for TDS as small doses can be delivered via this dosage system
highly dependent on patient factors
very few drugs can be delivered at a viable rate using this route due to low permeability
intra and intervariability

29
Q

What are counseling points to express with patches?

A

prepare skin to remove any dirt, lotions, oils or powders (affects adhesion)
if you tear or cut a patch, dont use it (unpredictable drug response)
using the palm of your hand, press down on the patch (patch should be smooth with no bumps or folds, loose fitting will affect penetration)
you may trim the hair if needed but avoid shaving the area of application (increased chances of irritation; broken skin may predispose higher drug exposure)
dont use a heating pad on your body when youre wearing a patch (increases absorption kinetics)
remove old patch before wearing a new one (risk of overdosing)
dispose of the old patch after first folding in half with sticky sides pressed together (reservoir will still have some drug content)

30
Q

What type of drugs are good candidates for transdermal delivery?

A

drug with high potency (<25mcg/day)
low molecular weight
lipophilic
short half-life
low melting point
high skin permeability
non-irritating and non-sensitizing
low oral bioavailability
low therapeutic index

31
Q

What are the types of transdermal delivery systems?

A

reservoir type
matrix type
drug-in-adhesive (DIA) type
-single layer DIA
-multilaminate DIA
dot-matrix

32
Q

What are the characteristics of the reservoir type TTS?

A

separate drug compartment: contains drug solution or suspension in a reservoir space
-formulation contains: drug dissolved/suspended in a solvent, liquid excipients, penetration enhancers
drug delivery control: membrane control the kinetic of release
follow zero-order kinetics
adhesive: face adhesive or in a concentric configuration on the perimeter

33
Q

What are the disadvantages of the reservoir type TTS?

A

adhesive and drug or adhesive and excipient interactions/incompatibilities can occur
vulnerable to burst release
-reasons: rupture of the membrane due to material defect, wear, inadvertent puncture

34
Q

What are the characteristics of matrix type TTS?

A

drug compartment:
-contains drug solution or suspension form in a matrix
-most simple design: a drug containing semisolid disc is held in contact with the skin by an adhesive tape
-formulation contains: drug dissolved/suspended in a semisolid, penetration enhancer
drug delivery control:
-rate controlling matrix and the stratum corneum (first order)
-no membrane
adhesive:
-matrix can itself act as an adhesive layer
-it can also be a separate layer

35
Q

What are the disadvantages of the matrix type TTS?

A

the protective overlay maybe mistaken for the part to be applied on the skin (unlikely if patient is properly trained/can also be avoided via clear labeling)
total patch surface area can be a lot larger than the actual drug delivery surface

36
Q

What are the characteristics of the drug-in-adhesive TTS?

A

drug compartment:
-contains the drug dissolved in an adhesive formulation
-represent the “state-of-the-art” in TTS design
-extremely comfortable
-patch is very thin
-maximum utilization of surface area of the patch
-formulation contains: drug dissolved in a PSA, adhesion composition must be customized for each drug
drug delivery control:
-rate controlling adhesive and the stratum corneum (first order kinetics)

37
Q

What are the disadvantages of drug-in-adhesive type TTS?

A

the first-order release characteristics (when drug concentration in adhesive falls, constant drug delivery profile is difficult to maintain)

38
Q

How can the first order kinetics problem of drug-in-adhesive type TTS be overcome?

A

multi-laminate DIA
-more drug can be released through the membrane in the upper DIA compartment into the lower DIA compartment

39
Q

Describe dot-matrix technology.

A

drug compartment: combination of 2 polymers
-acrylic: to hold the drug in high [ ]
-semisolid suspension: the microscopic drug-in acrylic droplets evenly dispersed in the non-compromised silicone adhesive
-formulation contains: drug dissolved in acrylic, adhesive (silicone polymer)

40
Q

What are the confusion factors contributing to errors with patches?

A

many different patch designs
dosage strength
frequency of administration
shape
size
color
site of administration
interchangeability

41
Q

Describe proper application of a patch.

A

peeling not just the protective layer but also the adhesive overlay
should be applied directly on the skin (remove old patch)
must remove the protective liner
location where the patch should be applied that is very critical especially for hormone patches

42
Q

What kind of patches are difficult to find on the body when its time to remove them?

A

clear patches

43
Q

What is an issue with pediatric patches?

A

cutting patches for a pediatric patient
-not possible with reservoir types but maybe done with matrix or DIA

44
Q

Why should you store a patch in a safe space?

A

may be appealing for young children

45
Q

What does a longer time between patches increase the risk for?

A

forgetting where the old patch is

46
Q

What is the indication for Exelon?

A

symptomatic treatment of mild to moderately severe Alzheimers dementia

47
Q

Describe the method of administration for Exelon.

A

once a day
to clean, dry, hairless, intact healthy skin on the upper or lower back, upper arm or chest

48
Q

What is the main force involved in iontophoresis?

A

the main force used to drive substances across the stratum corneum is the electrical driving force

PHAR224 (7 decks)

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