Some preparative variables influencing the properties of W/O/W multiple emulsions.

Water-in-oil-in-water multiple emulsions of chloroquine diphosphate were prepared, using olive oil, arachis oil, Span 80, gelatin, acacia and Tween 80. Emulsifiers were employed individually or in combination. An attempt was made to correlate preparative variables with stability and drug release of multiple emulsions of roughly comparative particle size. When the emulsions were satisfactorily stabilized by the optimum blend of surfactants the rate of release varied with the nature and/or combination of emulsifiers employed. The possible effects of phase-inversion temperature, spontaneous emulsification and liquid crystal stabilization on the systems have been discussed. The mechanism probably involved complex interfacial adsorption and hydrodynamic phenomena in the presence of natural oils, co-surfactants and natural stabilizers of individual HLB number, particularly when acacia is present in the system. This could be attributed to the existence of protein in some species of acacia, since there are about 130 species of acacia, the gummy exudations of which are considered official in compendia. The protein content could be a reasonable additional specification for acacia as an emulsifier.