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Pharmaceutics II Exam 2 > Part 4 - Transdermal Drug Delivery Systems > Flashcards

Part 4 - Transdermal Drug Delivery Systems Flashcards

1
Q

there are many different dosage forms available via the skin route.
name those that give SYSTEMIC effects and those that give LOCAL effects

A

systemic effects - transdermal patch

local- ointments, creams, lotions, topical solutions, pastes, liniments, powders, gels, tinctures, aerosols

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2
Q

what is percutaneous absorption?

A

the absorption of substances from outside the skin to positions beneath the skin (including entrance to the bloodstream)

remember: per in Latin means THROUGH

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3
Q

give the components of the stratum corneum of the skin

A

protein, water, lipid

40% protein (keratin)
40% water
20% lipid (triglycerides, free fatty acids, cholesterol, phospholipids)

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4
Q

name the types of skin penetration that can occur with a drug

A

-transcellular penetration
-intercellular penetration
-transappendageal penetration

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5
Q

differentiate between the types of skin penetration by a drug

A

transcellular = across cells. PASSIVE. no enzymes needed

intercellular - between cells. again - no energy or enzymes needed

transappendageal - penetration via hair follicles, sweat/sebum glands, and pilosebaceous apparatus

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6
Q

between the 3 types of skin penetration by a drug, which is the most common absorption mechanism?

A

intercellular penetration

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7
Q

paracellular penetration is also known as….

A

intercellular penetration

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8
Q

put the following in order from superficial to deep:

dermis
stratum corneum
epidermis

A

statrum corneum
epidermis
dermis

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9
Q

of the 3 penetration mechanisms, which does not happen naturally?

A

transappendageal penetration.
physically pushed through a hole (hair follicle, sweat/sebum gland, pilosebaceuos apparatus)

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10
Q

name 5 factors that affect percutaneous absorption

A

-drug
-area of application
-physiochemical attraction to the skin compared to the vehicle
-hydration of the skin
-medicated application period

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11
Q

explain how the drug itself is a factor that affects percutaneous absorption

A

the concentration – high concentration will mean fast absorption (Fick’s law)

liphophilic drugs penetrate better

ionization reduces penetration (PKA IS IMPORTANT)

small molecules (100-800MW) penetrate faster

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12
Q

for a transdermal patch, what is the ideal molecular weight for the drug? why?

A

400

MW 100-800 can penetrate

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13
Q

true or false

hydrophilic drugs undergo faster percutaneous absorption

A

FALSE - lipophilic

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14
Q

Explain how pka value of a drug affects percutaneous absorption

A

ionization will reduce penetration. therefore, we want to control the pH so the drug remains unionized

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15
Q

what is the thinnest area to apply a transdermal patch and thus has the quickest sbsorption

A

skin behind the ear

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16
Q

explain how the area of application of the drug on the skin is useful

A

can help to control the dose.

normally, all patches are the same dose. therefore, to increase the dose you would increase the area of application by applying 2 patches instead of 1

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17
Q

non polar or polar:

which drug will go the transcellular route? what about intercellular?

A

nonpolar drugs will go the transcellular route (if small)
and polar drugs will go the intercellular route
(unionized, but has polar functional groups)

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18
Q

what is the ideal partition coefficient for percutaneous absorption

A

1
good for solubility and for permeability

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19
Q

what kind of drug will go through the transcellular pathway of percutaneous absorption

A

only drugs that are lipophilic and small

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20
Q

true or false

all percutaneous absorption mechanisms are passive

A

FALSE - transcellular and intercellular are, but not transappendageal

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21
Q

which is more hydrophilic - the epidermis or the stratum corneum?

A

epidermis

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22
Q

explain the difference between absorption through the GI tract and absorption through the skin

A

for the GI, the drug first has to dissolve in aqueous phase and then partition through lipid phase

it is the opposite for skin absorption because the epidermis comes after the stratum corneum and the stratum corneum is more lipophilic

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23
Q

how can penetration through the skin be enhanced?

A

through use of a chemical enhancer to disrupt the phospholipids and make it easier for the drug to get through the stratum corneum

also, absorption can be enhanced through hydration of the skin

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24
Q

true or false

the drug should have a greater physiochemical attraction to the skin than to the vehicle

A

TRUE – so that the drug will leave the vehicle

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25
what is the "horny layer"? how does it affect drug absorption through the skin?
stratum corneum the thinner the stratum corneum, the greater percutaneous absorption
26
name 7 physiological conditions of the skin that may have an impact on the penetration of the drug
bonding sebum hydration thickness injury metabolism temperature
27
explain how "bonding" is a physiological condition of the skin that may have an impact on the penetration of the drug
the accumulation of bonding in the epidermis can decrease the initial transport of the drug
28
explain how sebum in the skin can affect the penetration of the drug through the skin
can alter the pH, and the amount and composition of sebum can alter the passage of the drug
29
true or false increased hydration usually decreases penetration rate
FALSE - usually increases
30
what can increase hydration?
occlusive dressings
31
how can hydration vary across the skin
the age of the skin the location of the skin the condition of the skin
32
where on our body is the skin very thin? where very thin? what does this say about the absorption rate?
thin = behind ear thick = palm of hand follows Fick's first law - very small thickness = easier absorption
33
explain how injury affects drug absorption through the skin
skin that is cut increases the penetration rate, but applying a transdermal patch may cause irritation and should be avoided
34
explain how metabolism can affect percutaneous drug absorption
1st pass effects used to be thought to be that drugs were destroyed at the FIRST ENCOUNTER to the body. however, this is not true anymore we don't normall have a lot of enzymes hanging around near our skin - they're in the liver. in theory tho, increased metabolism causes reduced penetration of the drug
35
name 2 factors that affect metabolism (skin)
-age -skin condition
36
what is the normal temperature of our skin?
~30 degrees celsius
37
name 3 percutaneous absorption enhancers
-chemical enhancers -iontophoresis -sonophoresis
38
explain how chemical enhancers enhance percutaneous absorption
the increase the skin permeability by REVERSIBLY damaging or altering the physiochemical nature of the stratum corneum. reduces its resistance to diffusion they cause hydration of the skin and the structure of the lipids and lipoproteins in the intercellular channels are altered
39
name 3 chemical enhancers
alcohol azone DMSO (dimethyl sulfur oxide)
40
explain how azone and DMSO differ in their functions as chemical enhancers
azone gets inserted between lipid bilayers which increases the permeation of the drug through the intercellular pathway DMSO SOLVATES the polar heads of the phospholipids which expands the aqueous region
41
differentiate between iontophoresis and sonophoresis. what are they used for?
used as percutaneous permeation enhancers. iontophoresis = delivery of a charged chemical compound across the skin membrane by using an ELECTRICAL FIELD sonophoresis = used at high frequency ultrasound to increase permeation. the sound waves increase the separation between the cells of the stratum corneum
42
__________ is(are) PHYSICAL method(s) of increasing drug permeation through the skin
iontophoresis and sonophoresis
43
define the major barrier of the skin
the stratum corneum
44
what are the percutaneous absorption models?
-in vivo studies (animals) -in vitro studies (2 layer models of the skin - side by side and up and down models. - follows Fick's first law)
45
explain the advantages/benefits of the 2 in vitro percutaneous absorption models available
the "up and down" model poses an issue when air gets to the top and becomes a barrier the "side by side" model solves this issue
46
in the side by side absorption model, the dermis faces the ___ compartment and the epidermis faces the _____ compartment in the up/down absorption model, the dermis faces __ and the epidermis faces ___
dermis faces donor compartment and epidermis faces receptor compartment epidermis faces down and dermis faces up
47
which has looser tissue - the epidermis or the stratum corneum
epidermis
48
"an application of physical-chemical properties to predict absorption expectation through biological membranes"
membrane permeability studies
49
according to membrane permeability studies.....
Fick's first law is followed. as conc of the drug increases, the rate of diffusion also increases
50
membrane permeability studies used what kind of invitro equipment?
the side by side model (with dermis facing donor compartment and epidermis facing receptor)
51
an early assessment of the passage of drugs across biological membranes
membrane permeability studies
52
"passive absorption mechanism"
Fick's first law
53
name and differentiate between the 2 transdermal delivery systems
matrix type (monolithic) membrane type monolithic system (matrix type) -- has a drug matrix layer between the backing and frontal layers membrane-controlled systems -- contains a drug reservoir (or pouch) usually in liquid or gel form, a rate-controlling membrane, and backing, adhesive, and protecting layers
54
true or false the membrane system cannot give zero order drug release
FALSE - IT CAN matrix type cannot
55
what does zero order mean
the rate does not vary with the increase or decrease of the concentration of the reactants (drug)
56
what is the 5 layer, bulky, matrix type patch?
Nitro dur
57
what component of transdermal delivery systems is included to ensure that the drug will only move unidirectionally?
the backing layer
58
true or false if the drug is capable of providing an adhesive, an additional adhesive layer is still needed
FALSE -- not needed in the case of matrix type, there is no adhesive layer and the drug itself serves as the adhesive
59
the drug reservoir for membrane type is a solution or gel. what about the drug layer in matrix type system?
it is a POLYMER
60
increased vehicle viscosity in transdermal delivery systems ____ diffusion coefficient
REDUCES
61
______concentration/solubility of a drug penetrates better in TDDS
high
62
true or false lower concentration gradient = better penetration
false higher concentration gradient = better penetration
63
which increase penetration -- nonaqueous vehicles or aqueous vehicles? in the case of TDDS
nonaqueous vehicles (occlusive)
64
in the case of TDDS, _ area causes increased absorption
increased area
65
name 6 design objectives for transdermal delivery systems
-deliver the drug for percutaneous absorption at therapeutic levels at optimal rate -contain med agents that can release from the system and partition into the stratum corneum -occlude the skin to ensure ONE WAY FLUX (dc/dt) into the stratum corneum -have therapeutic advantage over other dosage forms -not irritate or sensitize the skin -adhere well to the skin and have the size, appearance, and site placement that encourage acceptance
66
in order to ensure that the drug can be released from the system and partition into the stratum corneum........
it must have the necessary physiochemical characteristics
67
name 8 advantages of transdermal delivery systems **
-avoid GI absorption difficulties -substitute for oral administration -avoid first pass effect -noninvasive and no inconvenience of parenteral therapy -may be terminated fast -provide extensive therapy with a single application -extend the activity of the drugs having short half life -easily and rapidly used in emergencies
68
an advantage of TDDS is avoiding GI drug absorption difficulties. explain this further
-low pH -enzymatic activity -drug interaction with food/drink and other oral drugs
69
an advantage of TDDS's is that they extend the activity of drugs having a short half life. explain this further
there is a reservoir of drug in the delivery system and its release is controlled
70
drugs with ___ half life are not suitable to be formulated as a transdermal patch
long half life there's no point. if you already take 1 tablet a day you would still have to apply the patch every day or so
71
name 6 disadvantages of TDDS
-only potent drugs are suitable -contact dermatitis at application site -limited time that they can stay (due to rashes and sensitization) -variable intra and inter percutaneous absorption efficacy (everyone has different skin) -bacterial and enzymatic drug metabolism under the patch -complex tech/high cost
72
WHY can only relatively potent drugs be suitable candidates for drug delivery?
the skin is impermeable -- natural limit of drug entry
73
true or false TDDS are cheap and easy to make
false -- complex tech needed and expensive
74
true or false percutaneous absorption does not vary with the site of application
FALSE - it does vary
75
TDDS's should be applied to what kind of skin
clean and dry skin
76
true or false skin lotion should be used before applying a transdermal patch
FALSE has to be intact, original skin. lotion will impact the drug release from the patch
77
true or false transdermal delivery systems should NOT be physically altered by cutting
true
78
true or false a transdermal delivery system should always be worn for the full period stated in the product instructions
FALSE -- not the case for nitroglycerin bc of tolerance effect but for all other cases it is true
79
what should the patient do with a TDDS after they remove it? why?
fold it in half with the adhesives facing each other so it can't be reused. after 24 hrs there's still a lot remaining in the patch. ~20% used after 24 hours
80
why is skin irritation a major issue for TDDS
lot of excipients and any possible chemical enhancers
81
name 7 limitations of TDDS
-not for all drugs -limited time it can be affixed -variable inter and intra percutaneous absorption efficacy -skin rashes, sensitization -bacterial and enzymatic drug metabolism under the patch -complex tech/ high cost
82
what drugs can NOT be used in a transdermal patch
if the drug is not potent sometimes, drugs with a short half life require a loading dose, and transdermal patches can't deliver this high dose also kind of useless for drugs with long half lives
83
of the patches mentioned, which remains on the skin the longest
7 days - transdermal clonidine (Catapres-TTS)
84

Pharmaceutics II Exam 2 (7 decks)

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