Comparison of microencapsulation techniques for the water-soluble drugs nitenpyram and clomipramine HCl

In this investigation, the water-soluble drugs nitenpyram and clomipramine HCl were encapsulated using coacervation, solvent evaporation and film-coating. The effect of different process factors on the encapsulation efficiency and the release profile of the microparticles was evaluated. For coacervation it was shown that the core to wall ratio was the most important factor. For solvent evaporation using an w/o emulsion the type and concentration of the surfactant were the most important parameters for a successful encapsulation. Additionally the coated material was tested for its stability under different conditions as a powder or compressed into tablets. It could clearly be demonstrated that the coated drug substance exhibited a better stability then the uncoated material. The particles prepared by film-coating showed the best stability.