Release rate profiles of theophylline and insulin from stable multiple w/o/w emulsions

Stable multiple w/o/w emulsions have been prepared using various Pluronic F127:PAA complexes in the internal aqueous phases of these emulsions. Theophylline and I-125-insulin were incorporated into the internal aqueous phases of these stable multiple emulsions and their release rates studied. The release rates of theophylline from these emulsions were found to be related to the droplet sizes of the emulsions which in turn was dependent on the particle sizes of the Pluronic:PAA complex in the internal aqueous phase, and the type of lipophilic surfactant in the oil phase, The use of surfactants with different HLB values in the external aqueous phase did not affect the entrapment efficiency of these emulsions. The release rate of I-125-insulin from one of these emulsions was significantly slower than from I-125-insulin solution. The release pattern of I-125-insulin from this same emulsion after storage for three days was not significantly different from the newly-prepared emulsion. The results indicate that it is possible to formulate drugs such as theophylline and insulin in multiple w/o/w emulsions where we have found them to be stable and could thus be formulated for rapid onset of action or as sustained drug delivery system, depending on the choice of Pluronic:PAA complex in the internal aqueous phase and the type of lipophilic surfactant in the oil phase. (C) 1997 Elsevier Science Ireland Ltd.