PHAR224 > Dermatologicals > Flashcards

Dermatologicals Flashcards

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1
Q

What are the advantages and limitations of dermatological preparations?

A

advantages:
-applied directly to site of action
-avoids systemic side effects
-allows combinatorial treatment strategies
-lower dosages
disadvantages
-slow onset leading to longer treatment
-dependence of PC as topical formulation has to overcome the protective barrier of the skin at therapeutically effective concentrations
-may encounter disease specific limitations

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2
Q

What is the largest organ in the body?

A

the skin
-surface area: 2m squared (70kg)

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3
Q

What are the three layers of the skin?

A

epidermis
dermis
subcutaneous tissue

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4
Q

Describe the epidermis.

A

average thickness varies depending on part of the body (avg ~200um)
contains several cell layers
pH 5.5
composed mainly of keratinocytes which synthesize keratin, melanocytes and dendritic cells (immune cells)

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5
Q

What are the 5 layers of the epidermis?

A

stratum corneum (horny layer)
stratum lucidum (clear layer)
stratum granulosum (granular layer)
stratum spinosum (prickle cell layer)
stratum germinativum/basale (basal layer)

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6
Q

Describe the stratum corneum.

A

10-15 layers of flattened keratinized anucleated dead cells
average thickness: 10um
undergoes desquamation

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7
Q

What is the role of the stratum corneum?

A

major permeability barrier of the skin
controls percutaneous absorption

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8
Q

What is desquamation and why is it important?

A

skins way of recovering or healing from some type of damage
-cells from top outer layer are removed
-skin is optimally healthy when it has a normal rate of desquamation
-creates a barrier which enables skin to retain hydration and resist assault

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9
Q

Describe the stratum lucidum.

A

thin layer of translucent, extremely flattened cells, only visible in the thickest skin
anucleated cells
cytoplasm filled with filaments

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10
Q

What is the role of the stratum lucidum?

A

capability of the skin to stretch
contains a protein that is responsible for the degeneration of skin cells
lowers the effects of friction in skin

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11
Q

Describe the stratum granulosum.

A

1-5 layers of flattened, many-sided cells
keratinocytes contain keratohyalin granules which discharge a cement-like substance that bind cells together (barrier against foreign material)

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12
Q

What is the role of the stratum granulosum?

A

site of biochemical activity (bioreactor)

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13
Q

Describe the stratum spinosum.

A

cuboidal, many sided or flattened keratinocytes
keratinocytes contained filaments
subject to constant pressure and friction

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14
Q

What is the role of the stratum spinosum?

A

helps the skin resist abrasion

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15
Q

Describe the stratum germinativum.

A

cells held together by desmosomes
single layer of cuboidal or columnar cells
nucleated basal cells (undergo mitosis)
turnover time is 28 days (4 days in psoriasis)

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16
Q

What is the role of the stratum germinativum?

A

provides the germinal cells necessary for the regeneration of the layers of the epidermis

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17
Q

What is the composition of the dermis?

A

matrix of connective tissue
cells
vascular supply
neural supply
skin appendages (glands and follicles)

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18
Q

Describe the dermis.

A

thickness 3-5um
presence of nerves and blood vessels (provide O2 and nourishment)
pH 7.2

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19
Q

What is the role of the dermis?

A

support
thermoregulation
aid in sensation

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20
Q

What is the composition of the subcutaneous tissue?

A

fibrofatty layers
also houses immune cells like macrophages

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21
Q

What is the role of the subcutaneous tissue?

A

storing energy
connecting dermis to muscle and bone
insulating body
mechanical cushion

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22
Q

What happens to the hypodermis as you age?

A

hypodermis decreases in size and your skin starts to sag

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23
Q

What are the mechanical and protective functions of the skin?

A

mechanical:
-elasticity (can stretch 1.5x)
-maintain suppleness (stratum corneum must have 10-20% water)
protective:
-microbiological barrier (bacterio/fungistatic)
-chemical barrier (traffics cpds)
-radiation barrier
-heat regulator

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24
Q

How do eccrine glands provide cooling?

A

water evaporation of sweat

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25
What are the important aspects to target dermatological drug delivery?
pathophysiology of disease active ingredient characteristics intended therapy (localized v systemic) vehicle/drug delivery system
26
What is the physicochemical criteria for dermatological formulations?
stability of active ingredient stability of adjuvants rheological properties prevention of water loss or volatile cpds phase changes particle size, particle distribution of dispersed phase apparent pH
27
What is the cosmetic criteria for dermatological formulations?
pharmaceutical elegance easy transfer from container spreads readily and smoothly leaves no residue or stain adheres to treated area without being tacky or difficult to remove
28
What are the factors that influence selection of vehicle for optimum bioavailability?
skin disease or condition rate of the release of drug from vehicle promotion of percutaneous absorption requirement for occlusion short and long term stability of drug in base influence of drug on consistency of base
29
What are the four possible bases for ointments?
hydrocarbon bases absorption bases emulsifying bases water soluble bases
30
What is the definition of an ointment?
contains <20% water and volatiles and >50% of hydrocarbons, waxes, or PEGs as the vehicle for external application to the skin
31
What is the definition of a cream?
an emulsion semisolid dosage form that contains >20% water and volatiles and <50% of hydrocarbons, waxes, or PEGs as the vehicle for external application to the skin
32
What is the definition of a paste?
a semisolid dosage form that contains a large proportion (20-50%) of solids finely dispersed in a fatty vehicle for external application to the skin
33
What is the definition of a gel?
a semisolid dosage form that contains a gelling agent to provide stiffness to a solution or colloidal dispersion for external application to the skin -may contain suspended particles
34
Ointments are _____ preparations and mostly ____, but may contain dispersed or dissolved API.
semisolid greasy preparation' anhydrous
35
Creams are _____ preparations that contain both ___ phase and ____.
semisolid preparations oil phase and water
36
True or false: ointments and creams can be differentiated based on the viscosity of the formulation rather than the formulation
false
37
What are examples of non water washable bases?
oleaginous/hydrocarbon bases absorption bases W/O emulsion bases
38
What are examples of water washable vehicles?
O/W emulsions gels hydrophilic bases emulsifying bases
39
What is the other name for oleaginous bases?
hydrocarbon bases
40
Describe oleaginous bases.
hydrophobic greasy non-water washable occlusive: -increased hydration -enhanced percutaneous absorption due to increased retention on skin emollient (soften skins)
41
What is occlusion?
formation of an impermeable layer on the skin to prevent evaporation of water
42
What are advantages and disadvantages of oleaginous bases?
advantages: -very stable vehicles -non irritating -non sensitizing -high compatibility with drugs disadvantages: -greasiness -stain clothing -difficult to remove -low patient acceptance
43
What are the main ingredients of oleaginous bases?
liquids: -fats and fixed oils (can become rancid) -mineral oil semisolids -petrolatum (emollient, occlusive) solids: -waxes (stiffening agent, emollient properties) -paraffin (stable, non-reactive)
44
What are the additives for oleaginous bases?
penetration enhancers levigating agents
45
What are the properties of ideal penetration enhancers?
non-toxic, non-irritating, non-allergenic immediate and predictable effect and immediate recovery of the barrier property of the skin after removal doesnt cause loss of body fluids/electrolytes compatible with drugs and excipients good drug solvent cosmetically acceptable odourless, tasteless, colourless, and inexpensive
46
What is the mechanism of penetration enhancers?
fluidization of stratum corneum lipids
47
What are examples of penetration enhancers?
isopropyl myristate oleic acid oleyl alcohol
48
What is the use of a levigating agent?
liquid used as an intervening agent to aid the incorporation and particle size reduction of a powder into an ointment
49
How much of the final weight of a formulation can a levigating agent take up?
maximum 5% of final formulation
50
What is an example of a levigating agent used in oleaginous bases?
mineral oil
51
Do we need preservatives for oleaginous bases?
no -theres no water in the formulation
52
Describe fusion as a compounding method for oleaginous bases.
components are: 1. melted together 2. cooled with constant stirring until congealed tools: glass beaker, porcelain dish, stainless steel mortar, hot plate, jacketed vessel
53
True or false: when using fusion as a compounding method for oleaginous bases you must start heating in reverse order (starting with highest melting point)
false you can start with either lowest or highest melting point
54
Describe incorporation as a compounding method for oleaginous bases.
mixing of one semisolid formulation into another -in a mortar with pestle -on a slab with spatula geometric dilution
55
Describe incorporation of solid APIs or excipients as a compounding method for oleaginous bases.
in a mortar with pestle or on a slab with spatula geometric dilution or use a levigating agent API can be dissolved in an oil
56
What are the two possible packaging options for extemporaneous compounding of dermatologicals?
ointment jar Topi-Click for HRTs
57
What is a suggested AUX label to have on extemporaneously compounded dermatological?
for external use only
58
What are the options for a BUD of ointments?
nonaqueous=90 days (USP) 28 days (Medisca) *either is fine, 28 days is just more conservative*
59
Describe absorption bases.
non-water washable bases -hydrophobic -greasy -anhydrous; hydrophilic components provide water-absorbing properties -upon water addition form W/O emulsions -occlusive -emollient contain an oleaginous material and a W/O emulsifier so that they can absorb water or expand W/O emulsions
60
What is an example of a condition where absorption bases are used and why?
oozing conditions they are not easily removed with water
61
What are the main components of absorption bases?
similar to oleaginous bases: -fats and fixed oils -mineral oil -petrolatum -waxes other addition is the emulsifier helping in inducing a water absorbing capacity
62
What are examples of anhydrous bases?
glycerol monostearate and glyceryl monooleate -very weak emulsifying capacity cholesterol -commonly used in absorption bases
63
What is the use of anhydrous bases?
specialty compounding like HRTs
64
Describe lanolin as an absorption base.
can take up to 2x its weight of water acts as W/O emulsifier
65
What are additives for absorption bases?
antioxidants penetrations enhancers +/-=same as oleaginous bases
66
What are the properties of an ideal antioxidant?
effective at low concentrations stable soluble in the vehicle compatible with pharmaceutical excipients and wide range of drugs odourless, tasteless
67
What are the compounding techniques for absorption bases?
same as oleaginous bases (fusion or incorporation)
68
What is the levigating agent limit for absorption bases? What is the difference in levigating agent compared to oleaginous bases?
5% of the final formulation hydrophilic levigating agent (glycerol, propylene glycol) can be used -not used for oleaginous bases
69
Describe emulsifying bases.
water washable bases (water miscible) anhydrous bases containing O/W emulsifying agents cream-like appearance self-emulsifying emollient
70
What kind of emulsion is formed when you add water to an emulsifying base?
O/W
71
Which base is a soap replacement?
emulsifying bases
72
What are the main components of emulsifying bases?
all liquid, semisold, and solid excipient same as for oleaginous bases -fats and fixed oils -mineral oil -petrolatum and white petrolatum -waxes
73
What are additional components for emulsifying bases?
O/W emulsifiers, mostly surfactants
74
What are the additives for emulsifying bases?
same as oleaginous bases -antioxidants -penetration enhancers +/-
75
What is the compounding approach for emulsifying bases?
fusion method is more commonly applied incorporation technique is NOT frequently used to prepare primary bases but can be used for incorporating solid APIs to form final formulations
76
What kind of levigating agents are used in emulsifying bases?
hydrophilic levigating agents (glycerol or propylene glycol) emulsifying base can be used as levigating agent in most final formulations
77
What are the main components of a cream base?
oil phase: liquid, semisolid, solid excipients used for oleaginous bases -fats and fixed oils -mineral oil -petrolatum and white petrolatum -waxes PLUS water phase
78
What are the additional components for cream bases?
emulsifying agents, mostly surfactants
79
Describe w/o emulsions.
greasier than o/w emulsions non water washable emollient, cleansing action capable of absorbing oil-soluble compounds from skin
80
Describe o/w emulsions.
water washable soft non-occlusive moisturizing (increases water content-->restores hydration of the skin) more commonly seen medicated creams are o/w emulsions-->used as drug carriers since it allows higher penetration of drug compounds
81
What are the additives for emulsions?
antioxidants (oil and water soluble) penetration enhancers +/- preservative humectants
82
What kind of bases are readily attacked by bacteria and fungi?
topical bases that contain aqueous phases, carbohydrates and proteins
83
What can microbial growth do to a formulation?
spoil the formulation -toxic hazard -source of infection
84
What is the universal preservative?
there isnt one -not all preservatives will be compatible with the API
85
What are the essential requirements for preservatives?
compatible with all ingredients stable to heat and prolonged storage non-irritant non-sensitizing to human tissue
86
What is the role of humectants?
prevent product from drying out -withdraw moisture at high concentrations -increase the hydration of the skin at low concentrations
87
Differentiate between the oil-soluble and water-soluble antioxidants.
oil-soluble: -BHT and BHA -alpha tocopherol water-soluble: -ascorbic acid -sodium bisulfite
88
What are the compounding methods for cream bases?
method 1: fusion 1. hydrophobic components melted together (start with lowest mp) 2. hydrophilic components dissolved in the water phase and heated 5C higher than oil phase 3. water phase added to oil phase gradually with constant stirring 4. cooled with constant stirring until congealed method 2: incorporation -mixing of one semisolid formulation into another (geometric dilution)
89
Describe lotions.
emulsions, most cases are o/w but can be w/o key ingredients similar to creams (aqueous and oily phase, emulsifying agent)
90
Where are lotions typically applied?
hairy areas like the scalp (less viscous=easier to spread)
91
What are pastes?
oleaginous base with 20% or more solids suspended in base -different consistency
92
What are the main components of the base for pastes?
hydrocarbon bases: all liquid, semisolid and solid excipients used for oleaginous bases -fats and fixed oils -mineral oil -petrolatum and white petrolatum -waxes
93
Are pastes water washable?
non water washable -20-50% powder dispersed in fatty base -very stiff consistency (localize material to defined areas of the skin) -form a thick impermeable layer on skin (protective action)
94
What are the compounding methods for pastes?
fusion: used to prepare base incorporation: method of choice for final formulation -on glass slab due to thickness
95
True or false: it is practical to use a levigating agent for a paste
false
96
What are the properties of hydrophilic bases?
water washable bases condensation of polymers of ethylene glycol contain water-soluble components properties: -ointment like consistency (soften or melt on skin) -non occlusive, mix with skin exudates -do not stain clothes (greaseless) -non irritant -chemically stable -cannot take up more than 8% water
97
What are the incompatibilities of hydrophilic bases?
phenols, iodine, KI, tannic acid, silver, mercury and bismuth salts quaternary ammonium compounds and parabens (reduced preservative activity) inactivate bacitracin, penicillin
98
What are the advantages of hydrophilic bases?
anhydrous-->useful for drugs that hydrolyze good patient compliance (non staining, non occlusive)
99
What are the additives for hydrophilic bases?
antioxidants penetration enhancers +/- *no preservative or humectants because they are anhydrous*
100
What kind of antioxidants are used for hydrophilic bases?
water-soluble -ascorbic acid -sodium bisulfite
101
What are the compounding methods for hydrophilic bases?
mainly fusion -all PEG components should be liquidated for mixing -components are melted together, cooled with constant stirring until congealed -melting: start with lowest melting point
102
Describe gels.
water washable bases liquid-rich, two-component semi-solid colloidal systems natural or synthetic polymers form a 3D matrix throughout a hydrophilic liquid
103
What are the properties of gels?
dissolve in water good for hairy areas good for oily skin textures water-soluble drugs are easily incorporated either dissolved in the aqueous phase or dispersed in gel
104
What are the main components of gels?
natural gums -tragacanth, agar, pectin, alginates semi-synthetic or synthetic polymers -methylcellulose, etc
105
What is the issue with using natural gums for gels?
hazy appearance high stickiness microbial contamination
106
What is an emulgel?
emulsion either o/w or w/o which are incorporated into a gelling agent makes gels as suitable dosage form for hydrophobic drugs allows dual control of the drug release from formulation
107
What are the additives for gels?
antioxidants (water-soluble) penetration enhancers +/- (like propylene glycol) antimicrobial preservatives humectants
108
What is the compounding method for gels?
hydration -full hydration is slow, most of the time takes 24hrs -exact method depends on the type
109
What is Plastibase?
gelled mineral oil by addition of polyethylene unctuous base (stains, difficult to remove) consistency remains unchanged over a wide temperature range *drugs tend to release faster from Plastibase than petrolatum*
110
What temperature destroys the gel structure of Plastibase?
>90C
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