Sterile emulsions are required when the drugs are immiscible with the vehicle systems and when fatty substances should be administered intravenously. Emulsions should be formulated with a globule size range of 0.5–1 microns. Surfactants are commonly employed to emulsify the oily liquid and aqueous phase. They should be nontoxic and easy to sterilize.

Examples of such surfactants are lecithin and polysorbate. The important variables that should be taken into consideration are globule size, surface charge, zeta potential, pH, concentration of emulsifier and preservatives. All the ingredients should be sterilized prior to manufacturing. Manufacturing, filling and packing should be carried out under aseptic conditions.