Encapsulation of water-soluble drugs by a modified solvent evaporation method. I. Effect of process and formulation variables on drug entrapment

TLDR

Pseudoephedrine HCl was encapsulated in poly(methyl methacrylate) microspheres by a water/oil/water emulsification–solvent evaporation process in which an aqueous drug solution was first emulsified into a methylene chloride polymer solution, then into an external aqueous phase, and the organic phase was removed by evaporation to precipitate the polymer. Drug loading rose with higher theoretical loading, more organic solvent, polymer, and stabilizer, but fell when stirring time, continuous‑phase pH, or the volumes of internal and external aqueous phases were increased.

Abstract

Pseudoephedrine HCl, a highly water-soluble drug, was entrapped within poly (methyl methacrylate) microspheres by a water/oil/water emulsification-solvent evaporation method. An aqueous drug solution was emulsified into a solution of the polymer in methylene chloride, followed by emulsification of this primary emulsion into an external aqueous phase to form a water/oil/water emulsion. The middle organic phase separated the internal drug-containing aqueous phase from the continuous phase. Microspheres were formed after solvent evaporation and polymer precipitation. The drug content of the microspheres increased with increasing theoretical drug loading, increasing amounts of organic solvent, polymer and polymeric stabilizer, and decreased with increasing stirring time, increasing pH of the continuous phase and increased volume of the internal and external aqueous phase.