Step Emulsification Research Articles

The formulation-performance relationship of multiple emulsions and ocular activity

Multiple emulsions containing prednisolone were prepared using a two step emulsification technique. The effect of various concentrations of hydrophilic and lipophilic emulsifiers (Tween-20 and Span-60) in multiple emulsions based on liquid paraffin on the drug bioavailability and duration of action as a controlled release formulation was studied following instillation in the rabbit's eye. The parameter of ocular activity such as area under the intraocular pressure/time curve (AUC); time for maximum response (TMR) and half value duration (HVD) were assessed for the o/w/o and w/o/w multiple emulsions. It was found that the hydrophilic emulsifier reduced the bioavailability but increased the concentration of lipophilic emulsifier to bring about the reverse effect. Therefore the bioavailability of the drug can be controlled by the proper choice and concentration of the emulsifier in the preparation of emulsions. The hydrophile-lipophile balance (HLB) values calculated for a surfactant mixture in a multiple emulsion was found to be highly negatively correlated to the values of the parameters of ocular activity. Decreasing the HLB value of the surfactant mixture in a w/o/w emulsion favours the bioavailability; the intensity and duration of drug action.

Encapsulation and Prolonged Release Behaviour of W/O/W Type Multiple Emulsions

AbstractW/O/W type multiple emulsions were prepared by two step emulsification procedures using an oily lymphographic agent, lipiodol, as an inner oil phase and Pluronic F‐68 as a hydrophilic emulsifier contained in the outer aqueous phase. Span 80, Pluronic L‐64 and HCO‐60 were used as emulsifiers incorporating them into the inner oil phase. The phase volume of the inner and outer aqueous phases and the yield of the w/o/w type multiple emulsions were studied. The dissolution behaviour of the w/o/w type multiple emulsions were determined by a dialysis method employing cellulose tubing. The effect of emulsifier type and the amount of HCO‐60 on the stability and prolonged release behavior of the w/o/w type multiple emulsions with or without lecithin, was also examined. The results indicate the HCO‐60 is a better emulsifier than Span 80 or Pluronic L‐64. Its use improves the stability and the prolonged release behavior of w/o/w type multiple emulsions.