Creams

Creams

Creams are semisolid dosage forms containing one or more drug sub-stances dissolved or dispersed in a suitable o/w or w/o emulsion base. Creams are more fluid compared to other semisolid dosage forms, such as ointments and pastes. Creams have a whitish, creamy appearance, which is a result of scattering of light from their dispersed phases, such as oil globules. This distinguishes them from simple ointments, which are translucent.

Creams based on o/w emulsions are useful as water-washable bases, whereas w/o emulsions have emollient and cleansing action. As described earlier, an o/w cream with high water content is also known as a vanishing cream. Upon rubbing this cream on the skin, the external/continuous aqueous phase evapo-rates, leading to increased concentration of a water-soluble drug in the oily film that adheres to the skin. This increase in the concentration gradient of the drug across the stratum corneum promotes percutaneous absorption.

Creams based on w/o emulsions, such as cold cream, are useful as soft-ening and cleansing agents. The name, cold cream, refers to the cooling sensation associated with the slow evaporation of the dispersed aqueous phase. A cold cream, typically, also contains scents and is used to remove makeup. Other common cold cream components include mineral oil, jojoba oil, lanolin, glycerin, alcohol, borax, and beeswax in addition to antimicro-bial preservatives such as methylparaben and propylparaben.

The use of creams as drug delivery systems is associated with good patient acceptance. In addition to the general requirements for semisolid dosage forms, incorporation of drug in a cream requires that the drug should

Be soluble in desired concentration.

·           Have relatively wide therapeutic window since accurate dosing is difficult.

·           Not crystallize upon evaporation of water.