Dimethyl sulfoxide, dimethylformamide, etc. are added to such compositions as wetting agents. The range of absorbent hydrophobic bases is quite large. They are included in pharmacopoeias of many countries of the world. Emulsion bases. Depending on the nature of the base, physicochemical properties of surfactants and the value of hydrophilic-lipophilic balance (HLB) emulsion bases are divided into two groups: emulsion bases of the I type of oil-water type; emulsion bases of the II type of water-oil type. Emulsion bases of oil-water type are formed at certain ratios of hydrophobic components and water with the participation of one or more surfactants (GLB = 13-15), contributing to the formation of emulsions of the first kind. Such emulsions are tiny oil droplets uniformly distributed in water. They can be sodium, ammonium, triethanolamine soaps, alkyl sulfates, non-ionogenic surfactants (tweens, diethylene glycol stearate, etc.), sodium, ammonium and amine forms of bentonites, mixtures of anionic and non-ionogenic surfactants. Emulsion bases of water-oil type consist of hydrophobic substances, surfactants (GLB = 3-6) and water. Type II emulsions are tiny water droplets uniformly distributed in the oil. These emulsion bases include an alloy of petroleum jelly with aqueous lanolin, water-vaseline emulsion grease, etc. The number of emulsion bases of water-oil type used in the world practice for preparation of ointments is very large and there is no possibility to describe them in detail in this section. We will give only characteristic examples of such bases. The simplest emulsion bases include at least three components: emulsifier, hydrophobic substance and water. Depending on the purpose of the ointment and the properties of the drug substance, various additives may be introduced into the composition of emulsion bases.

Due to the specificity of the internal structure emulsion ointment bases have a number of very valuable properties: accelerate the absorption of medecines from ointments by the skin, easily applied to the skin and washed off, do not interfere with thee-plogaso-exchange of the skin, easily incorporate both water- and fat-soluble substances, etc. The best known emulsion base is aqueous lanolin. Aqueous lanolin is a thick viscous mass of yellow-white color consisting of 70 parts of anhydrous lanolin and 30 parts of water. Aqueous lanolin cannot be heated: like any emulsion system, it splits when heated. Emulsion bases are increasingly used in dermatological practice due to its ability to dramatically increase the absorption of skin drug substances included in the ointment. Emulsion bases of the water-oil type, applied to the skin in a sufficiently dense layer, impede skin transpiration and cause its maceration (softening) and warming, leading to increased blood saturation of the skin. Macerated and slightly hyperemic skin, in turn, is characterized by an increased ability to resorb medecines. Ointments prepared on emulsion bases, characterized by low viscosity, easily applied to the skin and easily removed from it, have a pleasant appearance. Their use has a favorable effect on the skin: reduces dryness, increases elasticity, reduces inflammatory response. Due to the significant water content, emulsion bases are cheaper than anhydrous fatty bases. The choice of ointment base depends on the object and nature of the disease, as well as on the physicochemical properties of the prescribed medecines.