Pharmaceutical Creams Overview

Creams

• Viscous semisolid emulsions for external use only
• Susceptible to microbial growth due to the presence of water
• Consists of medicaments which can be dissolved or suspended in either oil-in-water or water-in-oil cream base

Advantages of Creams

• Prolonged contact at the application site
• Non-sticky and easily washable
• Non-irritating on application to the skin
• Dry the injured area more quickly than ointment

Disadvantages of Creams

• Less hydrophobic, hence higher risk of contamination

Oil-in-water (o/w) Creams

• Also known as aqueous cream or vanishing cream
• Produced by synthetic waxes (e.g. macrogol, cetomacrogol)
• Thin, white, and smooth in consistency
• Water washable base for rapid absorption and penetration of drugs
• Examples: aqueous cream, cosmetic creams

Water-in-oil (w/o) Creams

• Also known as oily cream
• Produced by natural emulsifiers (e.g. beeswax, wool fat or wool alcohols)
• Creamy, white or translucent, and rather stiff
• Provide good emollient properties; not readily washable by water; gives a cooling sensation
• Examples: Cold cream

Distinguishing between O/W and W/O Cream

• Miscibility Test: O/W creams are miscible with water, while W/O creams are miscible with oil
• Microscopic Examination: O/W creams have colored droplets after staining with an oil-soluble dye, while W/O have colored backgrounds
• Microscopic Observation under UV radiation: O/W creams have droplets that fluoresce, while W/O creams have continuous phases that fluoresce
• Conductivity Measurement: O/W creams are conductors of electricity, while W/O creams are poor conductors

Oily Vehicles

• Mineral oils (paraffins): most widely used, complex mixtures of saturated hydrocarbons; occlusive; chemically inert; do not give good skin penetration
• Vegetable oils: plant sources (e.g. peanut, castor, olive and coconut); occlusive; give good skin penetration
• Synthetic oils

Mineral Oils (Paraffins)

• Commonly used types include soft paraffins, liquid paraffins, and hard paraffins
• White soft paraffin and yellow soft paraffin are used to thin or thicken products
• The choice of paraffin depends on the colors of the ingredients

Vegetable Oils

• Oxidation can be controlled by adding antioxidants such as:
  • Butylated hydroxyanisole (0.02~0.5% w/w)
  • Butylated hydroxytoluene (0.02~0.5% w/w)
  • Sodium metabisulphite (0.01~1% w/v)
  • Sodium sulphite (0.1% w/v)

Humectants

• Hydroscopic materials added to decrease water loss from creams
• Used at concentrations of 5 - 15%
• Examples: Glycerol (glycerin), Propylene glycol, Polyethylene glycol 300

Compounding Creams: Terminologies

• Mixing by Fusion: Melting together the fatty bases over a water bath before incorporating other ingredients
• Trituration: Incorporation into the base of finely divided insoluble powders or liquids
• Levigation: Incorporation of insoluble coarse powders into a base using a shearing force to avoid a gritty product

General Principles of Compounding Creams

• Hygiene: Clean all surfaces, spatulas, and equipment with ethanol
• Always make an excess: Make 2-4g extra to account for loss during the compounding process
• Check solubility: Determine which ingredients are soluble or miscible in the aqueous phase and which are soluble or miscible in the oily phase
• Prepare the fatty base: Melt the fatty base in an evaporating dish over a water bath at the lowest possible temperature; cool the fatty base to 60°C; add and mix other ingredients that are soluble/miscible with the oily phase
• Prepare the aqueous phase: Heat up the aqueous phase to 60°C; dissolve water-soluble ingredients in the aqueous phase
• Add disperse phase to continuous phase at the same temperature (60°C):
  • For O/W cream: pour oily phase into aqueous phase
  • For W/O cream: pour aqueous phase into oily phase
• Stir continuously to mix: Stir the resulting emulsion continuously, but not too vigorously, until the product sets.

Hospital Manufacturing Unit

• Make sure to follow aseptic techniques and maintain hygiene in the lab

Dimethicone Cream BPC 1973 (Master Formula)

• Liquid Paraffin BP (400g) - Oily phase
• Dimethicone 350 BP (100g) - Miscible with oily phase
• Cetrimide BP (5g) - Emulsifying wax
• Cetostearyl Alcohol BP (50g) - Emulsifying wax
• Chlorocresol (1g) - Preservative
• Freshly boiled and cooled purified water (444g) - Aqueous phase
• This is an o/w cream base

Explore the essentials of creams used in pharmaceuticals, including their advantages and disadvantages. This quiz covers the characteristics of oil-in-water and water-in-oil creams, detailing their formulations and uses. Test your knowledge on the various aspects of topical semisolid emulsions.