A cream is a preparation usually for application to the skin. Creams for application to mucous membranes such as those of the rectum or vagina are also used. Creams may be considered pharmaceutical products as even cosmetic creams are based on techniques developed by pharmacy and unmedicated creams are highly used in a variety of skin conditions (dermatoses). The use of the finger tip unit concept may be helpful in guiding how much topical cream is required to cover different areas. Creams are semi-solid emulsions of oil and water. They are divided into two types: oil-in-water (O/W) creams which are composed of small droplets of oil dispersed in a continuous phase, and water-in-oil (W/O) creams which are composed of small droplets of water dispersed in a continuous oily phase. Oil-in-water creams are more comfortable and cosmetically acceptable as they are less greasy and more easily washed off using water. Water-in-oil creams are more difficult to handle but many drugs which are incorporated into creams are hydrophobic and will be released more readily from a water-in-oil cream than an oil-in-water cream. Water-in-oil creams are also more moisturising as they provide an oily barrier which reduces water loss from the stratum corneum, the outermost layer of the skin.
- The provision of a barrier to protect the skin
- * This may be a physical barrier or a chemical barrier as with sunscreens
- To aid in the retention of moisture (especially water-in-oil creams)
- Emollient effects
- As a vehicle for drug substances such as local anaesthetics, anti-inflammatories ( NSAIDs or corticosteroids), hormones, antibiotics, antifungals or counter-irritants.
CompositionThere are four main ingredients of the cold cream:
- Thickening agent
Topical medication forms
- Cream – Emulsion of oil and water in approximately equal proportions. Penetrates stratum corneum outer layer of skin well.
- * Cold creams
- Ointment – Combines oil (80%) and water (20%). Effective barrier against moisture loss.
- Gel – Liquefies upon contact with the skin.
- Paste – Combines three agents – oil, water, and powder; an ointment in which a powder is suspended.