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Dosage - Exam 3 > Lecture 21 > Flashcards

Lecture 21 Flashcards

Parenteral Solid Dosage Forms (Topical; Transdermal) - Yeo

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
Q

creams

A

o/w or w/o emulsion

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26
Q

gels

A

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
Q

rigid foams

A

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
Q

components of transdermal drug delivery

A

backing membrane
drug reservoir containing drug molecules
rate-controlling microporous membrane
skin contact adhesive

29
Q

transdermal drug delivery basics

A

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
Q

permeability equation

A

log P is roughly equal to 2.7 + 0.71log Ko/w - 0.0061MW

31
Q

transdermal patches types

A

membrane modulated
adhesive dispersion
matrix dispersion

32
Q

membrane modulated patches

A

examples – scopolamine (transderm-scop); nitroglycerin (transderm-nitro)
backing membrane, drug reservoir, rate-controlling microporous membrane, adhesive

33
Q

adhesive dispersion patches

A

example - nitroglycerin (deponit)
backing membrane, drug reservoir, rate-controlling adhesive

34
Q

matrix dispersion patches

A

example - nitroglycerin (nitrodur)
backing membrane, drug + adhesive = matrix

35
Q

common active ingredients of patches

A

clonidine
ethinyl oestradiol, norelgestromin
fetanyl
lidocaine
lidocaine, epinephrine
nicotine
nitroglycerin
17b-oestradiol
oestradiol, norethindrone
oxybutynin
scopolamine
testosterone

36
Q

transdermal nitroglycerin (membrane-modulated)

A

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
Q

transdermal rivastigmine (adhesive dispersion)

A

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
Q

rivastigmine transdermal

A

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
Q

transdermal contraceptive (matrix dispersion)

A

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
Q

drug diffusion through skin

A

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
Q

factors affecting permeability

A

hydration
solubility of a drug in stratum corneum
excipients (solvents, surfactants)
pH

42
Q

hydration affecting permeability

A

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
Q

pH affecting permeability

A

affects drug ionization status

44
Q

penetration enhancement types

A

iontophoresis
electroporation
ultrasound
prodrugs
(chemical) penetration enhancers

45
Q

iontophoresis penetration enhancement

A

uses low voltage electrical current to drive charged drugs through the skin

46
Q

electroporation penetration enhancement

A

uses high voltage (short) to create transient pores in the skin
early stage, but very good

47
Q

ultrasound penetration enhancement

A

uses low frequency ultrasonic energy to disrupt the stratum corneum

48
Q

prodrugs penetration enhancement

A

make more lipophilic

49
Q

chemical penetration enhancers

A

alcohol, dimethyl sulfoxide (DMSO), surfactants, acetone, ethyl acetate

50
Q

ionic surfactants enhacing

A

disorder the lipid layer of stratum corneum to swell and/or leach out some of the structural components, thus reducing the diffusional resistance

51
Q

ascorbate, dithiothreitol enhancing

A

reducing agents
disrupt disulfide bonds of proteins in keratinized cells

52
Q

azone enhancing

A

nonpolar, oily liquid
fluidize intracellular lipid lamella region of stratum corneum

53
Q

dimethyl sulfoxide (DMSO)

A

dipolar solvent
enter aqueous region of stratum corneum, interact with the lipid polar heads to expand hydrophilic region between the polar heads

54
Q

dissolving microneedles

A

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
Q

separable microneedles

A

rapidly dissolvable backing layers
with weaker connections between the backing layers and the MN tips
based on a hydrogel backing layer

56
Q

hydrogel forming microneedles

A

have cross-linked hydrogel structure that can collect interstitial fluid upon skin application –> in-situ hydrogel

57
Q

hollow microneedles

A

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
Q

common application sites

A

chest (upper)
back (upper and lower)
upper arm (on the part facing out)
flanks (side of the body, abdomen levels) except for exelon

59
Q

common frequencies of patches

A

daily (nicotine, rivastigmine)
twice daily (diclofenac)
twice weekly
weekly (buprenorphine, clonidine, estradiol)
every 72h (fentanyl)

60
Q

common errors in patch admin

A

preparation
removal
application
monitoring
storage and disposal

61
Q

preparation errors

A

removal of the patch from the packaging
removal of the protective foil
alternation of the patch

62
Q

monitoring errors

A

influence of heat
patch displacement

63
Q

some patients do not realize

A
  • 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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