Ointment

An ointment is a viscous semisolid preparation used topically on a variety of body surfaces. These include the skin and the mucus membranes of the eye (an eye ointment), vagina, anus, and nose. An ointment may or may not be medicated.

The vehicle of an ointment is known as ointment base. The choice of a base depends upon the clinical indication for the ointment, and the different types of ointment bases are:

Hydrocarbon bases e.g. hard paraffin, soft paraffin
Absorption bases e.g. wool fat, beeswax
Water soluble bases e.g. macrogols 200, 300, 400
Emulsifying bases e.g. emulsifying wax, cetrimide
Vegetable oils e.g. olive oil, arachis oil, coconut oil

The medicaments are dispersed in the base and later they get divided after the drug penetration into the living cells of skin.

Ointments are homogeneous, semi-solid preparations intended for external application to the skin or mucous membranes. They are used as emollients or for the application of active ingredients to the skin for protective, therapeutic, or prophylactic purposes and where a degree of occlusion is desired.

Ointments are formulated using hydrophobic, hydrophilic, or water-emulsifying bases to provide preparations that are immiscible, miscible, or emulsifiable with skin secretions. They can also be derived from hydrocarbon (fatty), absorption, water-removable, or water-soluble bases.

Source: http://en.wikipedia.org/wiki/Ointment