Emulsions: dispersed system containing at least two immiscible liquid phases.Depending on their constituents, the viscosity can vary greatly and 
pharmaceutical emulsions can be prepared as liquid or semisolids.External emulsions: applied on skin & mucous membranes as lotion, cream, 
cosmetics, it usually w/o or o/w type according to area & lesion type.Dispersed phases are composed of small globules of liquid distributed 
throughout a vehicle in which it is immiscible.Formation of electrical potential at the droplet surface to ensure repulsion 
between approaching droplets.Formation of coherent film or thin layer around the dispersed globules that 
prevent coalescence and separation of dispersed liquid.Internal emulsions: intended for oral & parental administration & it usually 
o/w type e.g. vitamins, sex hormones castor oil emulsions.Oil in water (O/W) emulsions, which have an oleaginous internal phase & an 
aqueous external phase.Water in oil (W/O) emulsions, which have an aqueous internal phase & an 
oleaginous external phase 
3.Liquid emulsions may be used orally, topically or parenterally.Semisolid emulsions employed topically.According to phases emulsions can be classified into:
1.Emulsifying agent is important in stabilization of emulsion through:
1.Decrease the interfacial tension between two phases.Increase patient acceptance by masking the disagreeable taste.To give delayed release drug in multiple emulsions.Multiple emulsion (W/O/W) and (O/W/O).H.W// There three factors determined the type of emulsion??Increase the viscosity of the medium.Classification of emulsion according to their uses :
1.Advantages of emulsions:
1.Increase absorption of some drug.Some drug is unstable in other forms.?2.??2.3.4.?Notes:
????2.?2.3.4.