Preparation of Emulsion Base Abstract Ointments are semi-solid preparations made of medicaments and suitable bases, which are intended for external application to the skin. In this experiment, W/O and O/W types of emulsion bases is prepared. The emulsion bases include water phase, oil phase and emulsifier. The general method of preparation is melting oil phase and dissolving water phase separately, then mix them completely at the temperature of 80℃, and stirring until the mixture cool to R.M. Key words ointments, emulsion base, dosage forms Introduction Ointments are semi-solid preparations made of medicaments and suitable bases, which are intended for external application to the skin. Ointments bases recognized for use as vehicles distinguished into three general classes: the oleaginous, the emulsion bases, and the water-soluble bases. An ointment is intended for external application to the skin or mucous membranes. Ointments have a water number that defines the maximum amount of water that it can contain. 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 used topically on a variety of body surfaces. These include the skin and the mucous membranes of the eye (an eye ointment), chest, vulva, anus, and nose. An ointment may or may not be medicated. Ointments are usually very moisturizing, and good for dry skin. They have a low risk of sensitization due to having few ingredients beyond the base oil or fat, and low irritation risk. There is typically little variability between brands of generics and name brand drugs. They are often disliked by patients due to greasiness. [2] The vehicle of an ointment is known as the ointment base. The choice of a base depends upon the clinical indication for the ointment. The different types of ointment bases are: Hydrocarbon bases include hard paraffin, soft paraffin, microcrystalline wax and ceresine. Absorption bases include wool fat, beeswax. Water soluble bases include macrogols 200, 300, 400. Emulsifying bases include emulsifying wax, cetrimide The medicaments are dispersed in the base, and later they get divided after the drug penetration into the living cells of skin. The rate and extent of release of sorbic acid from 6 ointment bases were assessed. The amount of drug released depended on the composition of the base and the concentration of sorbic acid employed. The rate of release decreased in the following order: water soluble > o/w emulsion > oleaginous > hydrophobic > w/o emulsion base. [3] Methods 1. Preparation of O/W emulsion base Material Stearic acid Dose 4.8g Function Oil phase The regent of ammonium stearate Glycerol monostearate Liquid paraffin Vaseline Wool fat Triethanolamine Distilled water 1.4g 2.4g 0.4g 2.0g 0.16g Water Add up to 40g phase Add stearic acid, glycerol monostearate, liuid paraffin, Vaseline and wool fat into evaporating dish. The dish is heated to 80℃ in water bath until melting completely. Then dissolve triethanolamine in distilled water and heat it in 80℃ of water bath. Pour oil phase into water phase with stirring in 80℃ of water bath, then stirring it until it cool to R.M. The temperature of water phase should be higher than oil phase’s, or the oil phase will precipitate in low temperature. So the two types of liquids should be mixed at 80℃. The product of reaction of stearic acid and triethanolmine is O/W emulsifier. The mixture of oil phase and water phase is the process of emulsifier’s generation. 2. Preparation of W/O emulsion base Material Dose Function 本文来源：https://www.wddqw.com/doc/aa28d7d8b6daa58da0116c175f0e7cd185251853.html