7. Topical Products Flashcards
1
Q
Dermatologists aim at 5 main target regions:
A
- Skin surface
- Horny layer viable epidermis
- Upper epidermis
- Skin glands
- Systemic circulation
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
3
Q
Topical formulations - semisolids
A
- Ointments
- Creams (o/w & w/o)
- Gels (hydrogels, bioadhesive gels)
- Pastes
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
5
Q
Commonly used excipients
A
- Solvents/co-solvents
- Humectants - glycerol
- Emollients - lipids
- Permeation enhancers
- Antioxidants
- Buffers
- Emulsifers - Surfactanrs
- Antimicrobials - alcohols
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
7
Q
Classification of ointment bases (5)
A
- 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 - Fats & fixed oils:
- Non-volatile oils (vegetable origin)
- Decompose upon exposure to air, light & high temp
- Requires antioxidants - Absorption bases:
- Contain emulsifying ointment (surfactant)
- Bases soak up water while retaining their semi-solid consistency resulting in w/o emulsion - 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 - Water soluble bases:
- Do not contain hydrocarbons/oleaginous components
- Mix of high & low molecular weight PEG
- Non-occlusive & easily washed from skin surface
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
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
10
Q
Preparation of ointment - Fusion method
A
- Ingredients combined & melted together as they cannot be physically mixed
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
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
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
14
Q
Creams: Overview
A
- Viscous semisolid for external application
- Mainly suitable for wet & weepy skin conditions
- Preferred by patients
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
