Process and formulation variables in the preparation of wax microparticles by a melt dispersion technique. II. W/O/W multiple emulsion technique for water-soluble drugs.

Abstract

Pseudoephedrine HCl-carnauba wax microparticles were prepared by a multiple emulsion-melt dispersion technique. A heated aqueous drug solution was emulsified into the wax melt (W/O emulsion), followed by emulsification of this primary emulsion into a heated external aqueous phase (W/O/W emulsion). The drug-containing microparticles were formed after cooling and congealing of the wax phase. The encapsulation efficiencies were above 80 per cent and actual drug loadings close to 50 per cent were achieved. The surface of the microparticles had submicron pores and drug crystals were visible on cross-sections. The drug loading depended on the rate of cooling and the volume of the internal aqueous phase but was insensitive to the volume of the continuous phase. The drug release was much faster when compared to the release from polymeric microspheres.