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.