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The O/W emulsion solvent evaporation method was used to prepare
controlled release formation of drugs in this report. We
selected gelatin as emulsion agent. The microcapsules was
form by polymer solution（Ethylcellulose） containing drug
（Aspirin）.
There were seven variables, including the gelatin concentration,
the stirred speed, the ratio of polymer solvents, the viscosity
of Ethylcellulose,the addition of non-solvent in polymer
solution, the ratio of drug to shell and the re-use of
dispersion medium to prepads were investigated. The yield of
microcapsules, the particle sizes distribution, the drug
content, therelease rate, SEM and the release kinetics were
studied. The results indicated that the yield no longer
increased when the concentration of gelatinmore than 1%. The
average particle size was increased by decrease the stirred
speed.Increasethe ratio of drug to shell, not addition non-
solvent in polymer solution and re-use of dispersion medium
increased the drug content. Addition non-solvent in polymer
solution, decreasing the viscosity of Ethylcellulose and re-use
of dispersion medium increased the release rate. We observed the
surface character of microcapsule by SEM, and found that
the release rate reduced withthe fine surface structure. The
release rate behavior of microcapsules is more conform to fit
the Higuchi release model.
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