7. Topical Products Flashcards

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1
Q

Dermatologists aim at 5 main target regions:

A
  1. Skin surface
  2. Horny layer viable epidermis
  3. Upper epidermis
  4. Skin glands
  5. Systemic circulation
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2
Q

Rationales for topicals

A
  • Build up of the skin’s barrier function with emollients, sunscreens etc
  • Targeted delivery for skin’s outer layers - formulated to avoid systemic delivery
  • Systemic drug delivery via transdermal patches (avoids 1st pass metabolism)
  • Avoids GI tract
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3
Q

Topical formulations - semisolids

A
  • Ointments
  • Creams (o/w & w/o)
  • Gels (hydrogels, bioadhesive gels)
  • Pastes
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4
Q

Selection of excipients

A
  • Should be safe & FDA approved
  • Make up 90%+ of a topical product
  • Improve drug/formulation solubility, permeability & stability
  • Control drug release & permeation
  • Prevention of microbial growth
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5
Q

Commonly used excipients

A
  • Solvents/co-solvents
  • Humectants - glycerol
  • Emollients - lipids
  • Permeation enhancers
  • Antioxidants
  • Buffers
  • Emulsifers - Surfactanrs
  • Antimicrobials - alcohols
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6
Q

Ointments

A
  • Greasy preparations
  • Biphasic vehicles - anhydrous with the active dissolved/dispersed in the base
  • Occlusive - barrier to water loss
  • Acts as emollient - softens skin
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7
Q

Classification of ointment bases (5)

A
  1. Hydrocarbon/Oleaginous bases:
    - Consists of soft paraffin or mix of hard paraffin
    - Water & aqueous ingredients can be incorporated into such bases in small amounts with difficulty
    - Melting point between 38 & 60 degrees - increases with chain length
  2. Fats & fixed oils:
    - Non-volatile oils (vegetable origin)
    - Decompose upon exposure to air, light & high temp
    - Requires antioxidants
  3. Absorption bases:
    - Contain emulsifying ointment (surfactant)
    - Bases soak up water while retaining their semi-solid consistency resulting in w/o emulsion
  4. Emulsifying bases:
    - Oleaginous bases + high HLB surfactant (o/w)
    - Also known as water removable base
    - Anionic - emulsifying ointment
    - Cationic - cetrimide emulsifying ointment
    - Non-ionic - cetomacrogol emulsifying ointment
  5. Water soluble bases:
    - Do not contain hydrocarbons/oleaginous components
    - Mix of high & low molecular weight PEG
    - Non-occlusive & easily washed from skin surface
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8
Q

Selection of an appropriate base depends on:

A
  • Desired release rate of drug
  • Desirability for transdermal/topical drug effect
  • Stability of drug in ointment base
  • Effect of drug on consistency & other physical features of the base
  • Occlusive or washable nature
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9
Q

Preparation of ointment - incorporation method

A

Components of the ointment are mixed together until a uniform preparation has been obtained using:

  • Mortar & pestle
  • Spatula & ointment slab
  • Reduces particle size of solid - not gritty texture
  • Active may be added directly or by using compatible levigating agent
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10
Q

Preparation of ointment - Fusion method

A
  • Ingredients combined & melted together as they cannot be physically mixed
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11
Q

Challenges of Fusion method

A
  • Overheating can cause products to oxidise, discolour & degrade
  • Mix phases at same temp
  • High melting ingredients can solidify
  • Phase separation - reheat & stir
  • Low viscosity - add more high viscosity ingredients
  • Poor dispersion - reheat & add more surfactant

When reheating use minimal heat

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12
Q

Creams: O/W aqueous creams

A
  • When applied on skin it evaporates & generates cooling sensation
  • Non-occlusive but deposits moisturisers on the SC
  • Vanishing creams
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13
Q

Creams: W/O oily creams

A
  • Preferred over ointment due to easy of spreading & removing & less greasy
  • Occlusive layer forms on skin, reducing water evaporation - emollient effect
  • Emollient/cleansing creams
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14
Q

Creams: Overview

A
  • Viscous semisolid for external application
  • Mainly suitable for wet & weepy skin conditions
  • Preferred by patients
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15
Q

Gels

A
  • (Semi)solid system with 2 consitutients - cross linked polymeric structure interpenetrated by a liquid
  • Has low conc of gelato molecules (<15%)
  • Liquify upon contact with skin & then dry as a non occlusive film
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16
Q

Classification of Gels (2)

A
  1. Organogels - prepared with organic or water-insoluble oleaginous materials
  2. Hydrogels - Prepared with water or water-soluble materials
17
Q

Advantages & Disadvantages of Gels

A

Advantage: Easy to apply to hair bearing areas, non greasy

Disadvantage: Easily removed by perspiration, lack emollient & skin protective properties

18
Q

Hydrogels (3D)

A
  • Semisolid formulation having an external polar solvent phase immobilised within a 3D network structure - cross linked
  • Ability to absorb large amount of water & swell, while maintaining 3D structure
19
Q

Pastes

A
  • Ointment containing as much as 50% powder dispersed in a fatty base
  • High viscosity with good absorbing properties
  • Less greasy than ointment alone
20
Q

Ointment vs cream

A
  • Ointment used for very dry skin conditions

- Creams used for weeping skin conditions

21
Q

Barrier creams vs emollients

A
  • Barrier creams contain dimethicone (silicone) to protect against water soluble irritants
  • Silicone has water repellent properties
  • Emollients soften & smooth skin
  • Occlusive properties prevent water loss - correct drying
  • Contains oils & humectants
22
Q

Keratolytics (KT)

A
  • Helps with removal of outer layer of skin
  • Found in many topical products for acne, psoriasis
  • Enhances penetration of other topicals e.f. corticosteroids
  • E.g. Salicylic acid, urea, benzoyl peroxide
23
Q

Nail lacquers- Actives

A
  • Active ingredient is Ciclopirox (anti fungal)
24
Q

UV radiation (3)

A

UVA:

  • Longest wavelength 315-400 nm
  • Penetrates deep into skin surface
  • Release free radicals -> DNA mutation -> carcinogenic

UVB:

  • Longer wavelengths 289-315 nm
  • Reaches skin surface
  • Causes tanning, burning & skin ageing

UVC:

  • Short wavelength
  • 100-280 nm
  • Do not penetrate earth
25
Q

Types of sunscreens (2)

A

Chemical sunscreens:

  • Organic components that absorb UV
  • Susceptible to photo-degeneration & generate free radicals
  • Causes photo-irritant/sensitising reactions in susceptible individuals
  • E.g. Avobenzone, Oxybenzone

Physical sunscreens:

  • Inorganic components which reflect UV
  • Broad spectrum UVs
  • Benefit to those with skin sensitivity/irritiation
  • Poor dispersion
  • E.g. Oxides
26
Q

Sun Protection Factor (SPF)

A
  • Measure of sunscreen effectiveness
  • SPF = MED (protected skin) / MED (unprotected skin)
  • MED: Minimum amount of UV that produces redness 24 hours after exposure
  • SPF factors is not linear
  • Used to determine level of protection
27
Q

Sun exposure - personal & environmental factors

A
  • Individual response
  • UV index
  • Time of day
  • Index of exposure of that region of the body