Creams Flashcards
What is a cream?
Semi-solid emulsion (O/W) or (W/O)
What are the characteristics of a hydrophilic cream (O/W)?
Non-greasy
Miscible with skin secretions
H2O-washable
Non-occlusive
What are the characteristics of a lipophilic cream (W/O)?
Somewhat greasy
Less miscible with skin secretions than O/W
Less H2O-washable
Somewhat occlusive
What are the basic components of a cream?
Drug
Continuous phase
Dispersed phase
Emulsifier
What may it also contain?
Co-solvent
Thickener
Preservative
Penetration enhancer
pH regulator
Antioxidant
What does a co-solvent do?
Enhances solubility
What does a thickener do?
Enhances viscosity/stability/release profile
What does a preservative do?
Prevents microbial spoilage
What does a penetration enhancer do?
Enhances drug penetration
What does a pH regulator do?
Adjusts pH, reduces irritation
What does an antioxidant do?
Prevents oxidation degradation
What must happen to ensure sufficient dose + even dispersion?
Good solubility in either phase
What must happen to ensure stable emulsion?
Choice of suitable emulsifiers
Hydrophile-lipophile balance (HLB) + Bancroft’s rule
What is Bancroft’s rule?
High HLB emulsifier = O/W emulsion
Low HLB emulsifier = W/O emulsion
What is HBL?
Hydrophilic emulsifier = high >10
Lipophilic emulsifier = low <10
What is HBL matching?
Different oils have different HBL requirements for O/W + W/O emulsions
How do you do HBL matching?
Match requirement to emulsifier HLB
Use emulsifier blends
Most stable contain single emulsifier
How do you prepare a cream?
Dissolve lipophilic ingredients in oily phase, heat at minimum temp required
Dissolve hydrophilic ingredients in, aqueous phase, heat to same temp as oily
Mix both at same temp
Stir until thick emulsion
Incorporate solids by trituration
