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Dosage - Exam 3 > Lecture 21 > Flashcards

Lecture 21 Flashcards

Parenteral Solid Dosage Forms (Topical; Transdermal) - Yeo (63 cards)

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1
Q

stratum corneum

A

main barrier to permeation
brick and mortar model (dead cells and lipids)
deal cells are not permeable thus permeation occurs by partitioning through the lipid material between the dead cells
functions as a lipid barrier
state of hydration is directly related to the ease of permeation

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2
Q

living epidermis

A

viable epidermis
living cells without capillaries
cells get nutrition by diffusion from dermis
source of skin color and tanning

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3
Q

dermis

A

contains capillaries
drug needs to reach these capillaries to achieve systemic action
contains pain, thermal, and tactile sensors
injury must reach dermis to produce scarring

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4
Q

hair follicles and sweat glands

A

secondary route of drug absorption that bypasses the stratum corneum

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5
Q

functions of the skin

A

containment
microbial barrier
chemical barrier
radiation barrier
electrical barrier
thermal barrier and body temperature regulation

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6
Q

containment function

A

confine underlying tissues and restrain their movement

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7
Q

microbial barrier function

A

pH of the skin is 5 which inhibits the growth of bacteria
sebum contains bacteriostatic and fungistatic fatty acids (like propanoic, butanoic, hexanoic, and heptanoic acids)

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8
Q

chemical barrier function

A

permeability resistance of stratum corneum is several orders of magnitude greater than other barrier membranes of the body

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9
Q

radiation barrier function

A

expsoure to UV stimulates synthesis of melanin, which absorbs UV rays

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10
Q

electrical barrier function

A

offers high impedance to the flow of an electrical current
need to treat the skin with salt solutions and overcome the impedance to measure body potentials (like with ECG) – use granular salt suspensions, creams, pastes containing electrolytes

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11
Q

thermal barrier and body temperature regulation function

A

maintains 98.6F by dilating/contracting blood vessels or sweating

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12
Q

topical drug delivery

A

local effects on barrier function (surface effects and stratum corneum effects)
drug action on the skin’s glands
effects in deep tissue

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13
Q

transdermal drug delivery

A

systemic

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14
Q

surface effects of topical examples

A

zinc oxide paste for diaper rash
sun blocks and sunscreens
lip balms for chapped lips
calamine lotion for poison ivy and poison oak
antibiotics
deodorants
medicated sopas

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15
Q

stratum corenum effects of topical examples

A

emollicency (softening horny tissue)
keratolysis (chemical digestion and removal of horny tissue)

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16
Q

drug action on the skin’s glands examples

A

antiperspirants
acne
hair removers (depilatories)

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17
Q

antiperspirants example

A

aluminum chloride
irritate and close the orifice of eccrine glands to impede sweat flow

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18
Q

acne example

A

soap, alcoholic solutions, antibiotics
retinoids –> reset the process of epidermal proliferation and differentiation to prevent the formation of lesions

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19
Q

types of ointments

A

hydrocarbon bases (most hydrophobic)
silicone bases
absorption bases
water soluble bases (most hydrophilic)

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20
Q

hydrocarbon based ointments

A

most hydrophobic
examples – petrolatum and polyethylene dissolved in mineral oil (plastibase)

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21
Q

silicone based ointments

A

contain polydimethylsiloxane oil

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22
Q

absorption based ointments

A

ointment containing w/o emulsifiers
example - w/o emulsion containing aqueous solution of a drug

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23
Q

water soluble based ointment

A

most hydrophilic
example - polyethylene glycol ointment

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24
Q

pastes

A

ointments into which a high concentration of insoluble particulate solids (starch, calcium carbonate, talc) are added

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25
creams
o/w or w/o emulsion
26
gels
liquid phase trapped in matrix of a natural or synthetic polymer (like tragacanth, pectin, carrageenan, methylcellulose, carboxymethylcellulose, carbopol) example - topical scalp gels (not too greasy)
27
rigid foams
air or other gas emulsified in a liquid phase (like whipped cream) liquid phase may contain a drug example -- aerosol shaving creams, medicated quick-breaking antiseptic foams
28
components of transdermal drug delivery
backing membrane drug reservoir containing drug molecules rate-controlling microporous membrane skin contact adhesive
29
transdermal drug delivery basics
generally impenetrable (principle resistance is stratum corneum) permeability correlates with drug's MW and Ko/w useful for drugs with high skin permeability or low dose requirement may need frequent dosing if drug has a short systemic half-life/undergoes extensive first pass metabolism
30
permeability equation
log P is roughly equal to 2.7 + 0.71*log Ko/w - 0.0061*MW
31
transdermal patches types
membrane modulated adhesive dispersion matrix dispersion
32
membrane modulated patches
examples -- scopolamine (transderm-scop); nitroglycerin (transderm-nitro) backing membrane, drug reservoir, rate-controlling microporous membrane, adhesive
33
adhesive dispersion patches
example - nitroglycerin (deponit) backing membrane, drug reservoir, rate-controlling adhesive
34
matrix dispersion patches
example - nitroglycerin (nitrodur) backing membrane, drug + adhesive = matrix
35
common active ingredients of patches
clonidine ethinyl oestradiol, norelgestromin fetanyl lidocaine lidocaine, epinephrine nicotine nitroglycerin 17b-oestradiol oestradiol, norethindrone oxybutynin scopolamine testosterone
36
transdermal nitroglycerin (membrane-modulated)
half-life - 3 min slightly soluble in water, soluble in common organic solvents indication - prevention of angina pectoris (chest pain) due to coronary artery disease; not for immediate relief of acute attacks
37
transdermal rivastigmine (adhesive dispersion)
exelon patch (novartis) approved by the FDA in 2007 indication - memory problems (dementia) associated with alzheimer's disease or parkinson's disease if total daily dose is under 6mg then dose 4.6mg/24h patch if total daily dose is 6-12mg then dose 9.5mg/24h
38
rivastigmine transdermal
sparingly soluble in water, very soluble in ethanol, acetonitrile, n-octanol, ethyl acetate logP - 2.3 water solubility - 2.04mg/mL acrylic copolymer is poly(butylmethacrylate, methylmethacrylate)
39
transdermal contraceptive (matrix dispersion)
examples - ortho evra (d/c in 2014) and xulane 150mcg/day of norelgestromin and 35mcg/day EE components are backing layer (polymer layer for structural support), middle layer (adhesive, matrix, and active ingredients), and third layer (release liner) once a week for three weeks apply to upper outer arm, abdomen, buttock, or back
40
drug diffusion through skin
protein-rich cells (bricks) separated by thin layer intracellular lipids (mortar) three different ways: 1. across the cellular-intracellular regions in series 2. across the lipid intracellular spaces 3. across thin lipid layers sandwhiched between flattened protein cells
41
factors affecting permeability
hydration solubility of a drug in stratum corneum excipients (solvents, surfactants) pH
42
hydration affecting permeability
the more hydrated, the greater drug permeability water associated with polar head groups of lipid bilayer loosens the lipid packing and make the bilayer more fluid
43
pH affecting permeability
affects drug ionization status
44
penetration enhancement types
iontophoresis electroporation ultrasound prodrugs (chemical) penetration enhancers
45
iontophoresis penetration enhancement
uses low voltage electrical current to drive charged drugs through the skin
46
electroporation penetration enhancement
uses high voltage (short) to create transient pores in the skin early stage, but very good
47
ultrasound penetration enhancement
uses low frequency ultrasonic energy to disrupt the stratum corneum
48
prodrugs penetration enhancement
make more lipophilic
49
chemical penetration enhancers
alcohol, dimethyl sulfoxide (DMSO), surfactants, acetone, ethyl acetate
50
ionic surfactants enhacing
disorder the lipid layer of stratum corneum to swell and/or leach out some of the structural components, thus reducing the diffusional resistance
51
ascorbate, dithiothreitol enhancing
reducing agents disrupt disulfide bonds of proteins in keratinized cells
52
azone enhancing
nonpolar, oily liquid fluidize intracellular lipid lamella region of stratum corneum
53
dimethyl sulfoxide (DMSO)
dipolar solvent enter aqueous region of stratum corneum, interact with the lipid polar heads to expand hydrophilic region between the polar heads
54
dissolving microneedles
type of polymeric MN that can degrade or dissolve post-insertion into the skin, leading to the delivery of the encapsulated drug at site of application
55
separable microneedles
rapidly dissolvable backing layers with weaker connections between the backing layers and the MN tips based on a hydrogel backing layer
56
hydrogel forming microneedles
have cross-linked hydrogel structure that can collect interstitial fluid upon skin application --> in-situ hydrogel
57
hollow microneedles
each needle incorporates a hollow cavity within and a bore on the needle tips, to which small volume of drug solutions can be injected
58
common application sites
chest (upper) back (upper and lower) upper arm (on the part facing out) flanks (side of the body, abdomen levels) except for exelon
59
common frequencies of patches
daily (nicotine, rivastigmine) twice daily (diclofenac) twice weekly weekly (buprenorphine, clonidine, estradiol) every 72h (fentanyl)
60
common errors in patch admin
preparation removal application monitoring storage and disposal
61
preparation errors
removal of the patch from the packaging removal of the protective foil alternation of the patch
62
monitoring errors
influence of heat patch displacement
63
some patients do not realize
- patch must be applied directly to the skin (not taped on top of each other) - must remove the protective liner - need to use one patch at time - where to place (rec - rotate the area of application to avoid skin irritation) - when to change - transparent parents - tts: transdermal therapeutic system - pediatric patch issue: some patches cannot be cute

Dosage - Exam 3 (9 decks)

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