Paraffin anhydrous ointment bases

Anionic emulsifying wax (3-30%) may also be mixed with soft and liquid paraffins to prepare anhydrous ointment bases such as emulsifying ointment BP. A preparation of 80% anionic emulsifying wax in white soft paraffin has been used as a soap substitute in the treatment of eczema. 

In its strictest definitive form, an ointment is classified as any semi-solid containing fatty material and intended for external application (U.S. Pharmocopeia, USP). In this discussion, ointments will be defined as semisolid anhydrous external preparations. In the nineteenth century, ointments were based on lard, a compounding material, the usefulness of which was severely limited by its tendency to turn rancid. Early in the twentieth century, lard was replaced by petrolatum (white or yellow soft paraffin or petroleum jelly). In present practice, nonmedicated ointments (ointment bases) are used alone, for emollient or lubricating purposes, or in combination with a drug for therapeutic purposes. 

Ointments are similar to creams but may be more viscous. Many ointments are prepared from a base of anhydrous lanolin or white petrolatum, which is a mixture ofn-, iso-, and cyclic-paraffins. Waxes may be added to make the ointments harder. 

Foundations are usually mixtures of a suspension and an emulsion (termed sus-poemulsiori) in which the emulsion portion is usually either O/W or W/O and the continuous phase generally contains the pigment particles. Foundations need to be formulated to be thixotropic to provide the desired smooth levelling effect. Ointments are similar to creams but may be more viscous. Many ointments are prepared from a base of anhydrous lanolin or white petrolatum, which is a mixture of iso- and cyclic paraffins. Waxes may be added to make the ointments harder. 

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