Preparation of double-encapsulated microcapsules for mitigating drug loss and extending release

The double-encapsulated microcapsules were prepared by the non-solvent addi tion, phase-separation method to form core material and, encapsulated with the O/W emulsion non-solvent addition method to increase drug loading and r egulate drug release rate. The drug used was theophylline, which is water-s oluble. Dichloromethane and n-hexane were used as the solvent and nonsolven t, respectively. This study investigated how various core material and micr ocapsule EC/TH ratios affect the drug loss, particle size, surface morpholo gy and release rate. The drug loss of the double-encapsulated microcapsules was 12.8% less than that of microcapsules prepared by the O/W emulsion non -solvent addition method alone. The particle size of these double-encapsula ted microcapsules decreased as the concentration of EC polymer was increase d in the second encapsulation process. The roughness of their surface was a lso in proportion to the concentration of polymer solution used in the seco nd encapsulation process. The dissolution study showed that the T-20 of the double-encapsulated microcapsules ranged from 2-35.4 h, while that of the O/W emulsion non-solvent addition method microcapsules was from 2.7-7.7 h. The greater the level of EC in the polymer solution, the slower the release rate of the drug from the microcapsules when the EC was not over the criti cal amount.