Microsoft Word - 60

Topical drug delivery is defined as the application of pharmaceutical dosage form to the skin for direct treatment of cutaneous disorder or the cutaneous manifestation of the general disease, with the intent of confining the pharmacological or other effect of the drug to the surface of the skin. Topical drug delivery systems include a large variety of pharmaceutical dosage form like semisolids, liquid preparation, sprays and solid powders. Most widely used semisolid preparation for topical drug delivery includes gels, creams and ointments. A gel is a cross-linked polymer network swollen in a liquid medium. Its properties depend strongly on the interaction between solid state polymer and the liquid component. Gels exhibit no steady-state flow. The interaction between polymer and the liquid dispersion medium form an interlacing three dimensional network of particles of dispersed phase. The increased viscosity caused by interlacing and consequential internal friction is responsible for the semisolid state. Topical gel formulation provides a suitable delivery system for drugs because they are less greasy and can be easily removed from the skin. Gel formulation provides better application property and stability in comparison to cream and ointments.