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PHRM 100 – PDD > PDD 12: Semi-Solid Dosage Forms – Dermatological Vehicles > Flashcards

PDD 12: Semi-Solid Dosage Forms – Dermatological Vehicles Flashcards

1
Q

What are the 2 components of the dermal drug delivery system?

A

(both should be physically, chemically, and microbiologically stable)

  • drug
  • excipients – humectants, emollients, penetration enhancers, preservatives
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2
Q

Describe characteristics of physical stability of drugs and excipients. (5)

A
  • viscosity and extrudability is maintained
  • no loss of water or other volatile components
  • homogenous phase distribution
  • no change in particle size distribution of the dispersed phase
  • release of drug unchanged
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3
Q

Describe characteristics of chemical stability of drugs and excipients. (3)

A
  • visual appearance (colour) maintained
  • no development of odour or loss of fragrance
  • pH maintained
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4
Q

Describe characteristics of microbiological stability of drugs and excipients. (2)

A
  • no growth
  • no development of odour
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5
Q

What are the challenges associated with dermal drug delivery in pharmacy? (3)

A
  • self-medication – numerous products available OTC, different formulations for the same drug
  • non-compliance and overuse
  • addition of drugs (ie. active ingredients) to existing products
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6
Q

What are humectants?

A

draw water from the dermis into the epidermis as opposed to drawing it from the atmosphere – acts to hold moisture in the striatum corneum

  • ie. urea, glycerin, PEG, lactic acid, propylene glycol, sorbitol, retinol (vitamin A), pantothenol (vitamin B5)
  • ie. application of 10% urea cream can double the amount of water in the striatum corneum
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7
Q

What are emollients?

A

provide an occlusive layer and trap insensible perspiration, and also mimic the effects of intercellular lipids, restoring suppleness of the skin

  • ie. oils, lipids, waxes, fatty acids, greasy ointments
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8
Q

What are penetration enhancers?

A

cosolvents and surfactants

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9
Q

Penetration Enhancers

What are cosolvents?

A

influence intercellular lipids

  • ie. ethanol, propylene glycol
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10
Q

Penetration Enhancers

What are surfactants?

A

lecithin (phosphatidylcholine and fatty acid diglycerides) may alter intercellular lipids

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11
Q

Penetration Enhancers

What is dimethyl sulfoxide (DMSO)?

A

very powerful solvent that penetrates skin readily – drugs dissolved in DMSO will also penetrate the skin

  • theory: stratum corneum retains DMSO and drugs then dissolve in the DMSO, alters keratin conformation, distorts and swells stratum corneum
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12
Q

What are preservatives

A

creams and lotions containing oils and/or water require preservatives to prevent
microbial growth

  • ie. methyl/propyl parabens, benzyl alcohol, chlorobutanol, chlorocresol, benzalkonium chloride
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13
Q

What are the 4 types of dermatological bases?

A
  • oleagenous base
  • absorption base
  • emulsion base
  • water soluble base
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14
Q

What is an oleagenous base (hydrocarbon base)?

A

oil

  • used for their emollient effect (do not allow escape of moisture)
  • water-free and can absorb very small amounts of water
  • retained on skin for prolonged periods
  • difficult to wash off with water
  • ie. petrolatum (vaseline) – mix of semisolid hydrocarbons from petroleum
  • ie. white petrolatum – decolourized petrolatum
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15
Q

Emulsions Recap

A
  • since the outer phase of the O/W emulsion is water, we can wash it off with water – however, there are still oil droplets in the “wash-off”
  • to make an emulsion thermodynamically stable, we normally use surfactants
  • surfactant stabilizes the oil droplet – if we add more and more water, then we will dilute the surfactant (rinse it out of the droplet surface), and it cannot stabilize the droplet anymore
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16
Q

What is an absorption base?

A

oil to water in oil

  • permit incorporation of water
  • insoluble in water – greasy
  • useful as emollients – not as good as hydrocarbon bases
  • useful to incorporate aqueous solution of drugs
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17
Q

What are the 2 types of absorption bases?

A
  • anhydrous but hydrophilic
  • W/O emulsions
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18
Q

Absorption Bases

What are anhydrous but hydrophilic bases?

A
  • incorporate water to form W/O emulsions
  • contains emulsifier only
  • ie. hydrophilic petrolatum, anhydrous lanolin
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19
Q

Absorption Bases

What are W/O emulsion bases?

A
  • can absorb more water
  • contains emulsifier and water
  • ie. lanolin (hydrous), cold cream
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20
Q

Absorption Bases

What are some examples? (5)

A
  • hydrophilic petrolatum
  • aquabase
  • simple ointment
  • eucerin
  • nivea
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21
Q

Absorption Bases

Hydrophilic Petrolatum

  • components
  • type of absorption base
A
  • white wax, cholesterol, stearyl alcohol, white petrolatum
  • forms W/O emulsion
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22
Q

Absorption Bases

Aquabase

  • components
  • type of absorption base
A
  • petrolatum, mineral oil, mineral wax, lanolin alcohol, cholesterol
  • forms W/O emulsion
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23
Q

Absorption Bases

Simple Ointment

  • components
  • type of absorption base
A
  • wool fat, hard paraffin, cetostearyl alcohol, white soft paraffin
  • forms W/O emulsion
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24
Q

Absorption Bases

Eucerin

  • components
  • type of absorption base
A
  • water, mineral oil, ceresin, lanolin, alcohol, methylchloroisothiazolinone
  • already a W/O emulsion
25
Q

Absorption Bases

Nivea

  • components
  • type of absorption base
A
  • paraffinum liquidum (mineral oil), PEG-150 (thickener, solvent, emulsifier, and surfactant), simethicone (synthetic silicone-based moisturizes, film former), parabens (preservative), BHT (antioxidant), natural and synthetic fragrances (might be contact allergens and sensitizers)
  • already a W/O emulsion
26
Q

What is an emulsion base (water removable base)?

A

oil in water (O/W)

  • not soluble in water, but can be washed from skin
  • often referred to as creams due to appearance
  • may be diluted with water or aqueous solutions
  • can absorb any discharge due to dermatological conditions
27
Q

Emulsion Base (Water Removable Base)

What are some examples? (3)

A
  • vanishing cream
  • hydrophilic ointment
  • glaxal base
28
Q

How can we determine if an ointment is W/O or O/W? (3)

A
  • conductivity test
  • dye solubility test
  • dilution test
29
Q

What is a conductivity test?

A

more conductive if water, so the continuous (outer) phase is water, then high conductivity

30
Q

What is the dye solubility?

A

add a water-soluble dye, will stain the emulsion if it is the outer phase (O/W), otherwise not

31
Q

What is the dilution test?

A

only O/W emulsions can be diluted with water

  • W/O need oil to dilut
32
Q

What is a water soluble base?

A

water

  • contains soluble components or may include gelled aqueous solutions
33
Q

Water Soluble Bases

What is the major/only component?

A

polyethylene glycol (PEG)

  • commonly used PEGs are PEG 1500, 1600, 4000, 6000
  • range from soft to hard waxy materials
  • get best results if PEGs with different MWs are blended
34
Q

Water Soluble Bases

What is it idea to incorporate?

A

non-aqueous or solid substances

  • aqueous solutions are not effectively incorporated – soften too much
  • only up to 8% water uptake, then lose their desired physicochemical properties
35
Q

Other Bases: Hydrogels

What are the 2 types?

A
  • lubricating gels
  • pluronic gels
36
Q

Other Bases: Hydrogels

What are lubricating gels?

A

consists of methyl cellulose, carbopol, propylene glycol, methyl paraben, NaOH, water

37
Q

Other Bases: Hydrogels

What are pluronic gels?

A

triblock copolymer (PEO-PPO-PEO)

  • form thermo-reversible gels in water
  • liquid at cold temperature
  • semi-solid gel at warm temperature – form micelles in water – with increased temperature, the hydrated corona (ie. the outer layer of micelle) dehydrates resulting in aggregation of micelles into a 3D network
38
Q

Other Bases: Penetration Enhancement Bases

What are they used for?

A

commonly used for topical application of NSAIDS

  • ie. diclofenac
39
Q

Other Bases: Penetration Enhancement Bases

What are the 2 types?

A
  • plo gel
  • phlojel
40
Q

Other Bases: Penetration Enhancement Bases

What is plo gel?

A

pluronic lecithin organogel

  • composed of pluronic gel, lecithin (solubilizer and penetration enhancer) and isopropyl palmitate (solubilizer and emollient)
41
Q

Other Bases: Penetration Enhancement Bases

What is phlojel?

A

composed of pluronic, lecithin, isopropyl palmitate, preservatives, antioxidants, water

42
Q

Other Bases: Liquid Preparations

What are the 3 types?

A
  • solutions
  • suspensions
  • emulsions
43
Q

Other Bases: Liquid Preparations

What are solutions?

A

contain mixtures of excipients such as propylene glycol, water, ethanol, glycerin, isopropyl alcohol, DMSO

  • ie. betnovate scalp treatment – betamethasone valerate, carbomer, isopropyl alcohol, NaOH, water
  • ie. pennsaid – diclofenac, glycerin, propylene glycol, ethanol, water, DMSO
44
Q

Other Bases: Liquid Preparations

What are suspensions?

A

contain mixtures of wetting agents, flocculating agents, viscosity inducing agents, preservatives, cosolvents, water

45
Q

Other Bases: Liquid Preparations

What are emulsions?

A

typically are oil in water (O/W) emulsions containing emulsifying agents, an oil phase, water, and preservatives

46
Q

Oleaginous Base

  • soluble in water
  • water washable
  • absorb water
  • anhydrous/hydrous
  • occlusive
  • greasy
  • example
A
  • soluble in water: NO
  • water washable: NO
  • absorb water: NO
  • anhydrous/hydrous: ANHYDROUS
  • occlusive: YES
  • greasy: YES
  • ie. white petrolatum, white ointment
47
Q

Absorption Forms W/O Emlusion Base

  • soluble in water
  • water washable
  • absorb water
  • anhydrous/hydrous
  • occlusive
  • greasy
  • example
A
  • soluble in water: NO
  • water washable: NO
  • absorb water: YES
  • anhydrous/hydrous: ANHYDROUS
  • occlusive: YES
  • greasy: YES
  • ie. hydrophilic petrolatum, aquabase, aquaphor, polysorb
48
Q

W/O Emulsion Base

  • soluble in water
  • water washable
  • absorb water
  • anhydrous/hydrous
  • occlusive
  • greasy
  • example
A
  • soluble in water: NO
  • water washable: NO
  • absorb water: YES
  • anhydrous/hydrous: HYDROUS
  • occlusive: YES
  • greasy: YES
  • ie. nivea, lanolin (hydrous), eucerin, cold cream
49
Q

O/W Emulsion Base

  • soluble in water
  • water washable
  • absorb water
  • anhydrous/hydrous
  • occlusive
  • greasy
  • example
A
  • soluble in water: NO
  • water washable: YES
  • absorb water: YES
  • anhydrous/hydrous: HYDROUS
  • occlusive: NO
  • greasy: NO
  • ie. glaxal base, hydrophilic ointment, dermabase, velvachol, unibase
50
Q

Water Soluble Base

  • soluble in water
  • water washable
  • absorb water
  • anhydrous/hydrous
  • occlusive
  • greasy
  • example
A
  • soluble in water: YES
  • water washable: YES
  • absorb water: YES
  • anhydrous/hydrous: HYDROUS/ANHYDROUS
  • occlusive: NO
  • greasy: NO
  • ie. PEG ointment
51
Q

Aqueous Gel Base

  • soluble in water
  • water washable
  • absorb water
  • anhydrous/hydrous
  • occlusive
  • greasy
  • example
A
  • soluble in water: YES
  • water washable: YES
  • absorb water: YES
  • anhydrous/hydrous: HYDROUS
  • occlusive: NO
  • greasy: NO
  • ie. carbomer gels, methocellulose gels, pluronic gels, gelatin gels, alginate gels
52
Q

Why do we need to be cautious when diluting a commercially available topical product with a base?

A

could result in precipitation and/or degradation of the drug

  • if the commercial product contains a cosolvent, addition of a base may dilute the cosolvent, resulting in reduced solubility of the drug in the formulation
  • dilution with a different base may result in a change in pH or the addition of excess water which may lead to drug degradation
  • addition of a base may result in anion-cation complexations and subsequent precipitation – often happens with preservatives (ie. sulphacetamide sodium and benzalkonium chloride)
53
Q

What are the 2 things to consider when selecting a dermatological vehicle?

A
  • optimization of drug delivery factors
  • patient and skin disorder factors
54
Q

Selecting a Dermatological Vehicle

Optimization of Drug Delivery Factors

A
  • drug must have some solubility in the vehicle or drug dissolution will retard percutaneous absorption and may become rate limiting
  • the drug must be stable in the vehicle (see previous slide)
  • components of the vehicle may enhance percutaneous absorption (ie. permeation
    enhancers and occlusive vehicles)
55
Q

Selecting a Dermatological Vehicle

Patient and Skin Disorder Factors

A
  • site of application – hairy, non-hairy, dry, oily, skin fold, thickness
  • patient acceptance – what will the patient like to use
  • type of wound – severity, protection, moist
56
Q

What are the advantages and disadvantages of cream as a dermatological vehicle?

A

advantage:

  • cosmetically elegant

disadvantage:

  • less absorption
57
Q

What are the advantages and disadvantages of lotion as a dermatological vehicle?

A

advantage:

  • evaporates well
  • good for large areas
  • good for hairy areas

disadvantage:

  • alcohol base will sting/irritate
58
Q

What are the advantages and disadvantages of gel as a dermatological vehicle?

A

advantage:

  • good for hairy areas
  • good for oily skin

disadvantage:

  • alcohol base will sting/irritate
59
Q

What are the advantages and disadvantages of ointment as a dermatological vehicle?

A

advantage:

  • excellent penetration
  • emollient effect
  • little or no irritation

disadvantage:

  • cosmetically less acceptable
  • thick greasy

PHRM 100 – PDD (14 decks)

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