RESUMO
OBJECTIVE: To prepare morphine-loaded chitosan microspheres by emulsion ionic cross-linking and investigate the effect of initial morphine quantity and different cross-linking degrees on drug loading, encapsulation efficiency and in vitro drug release. METHODS: Chitosan (with a relative molecular mass of 50,000 and deacetylation degree no less than 90%) at 100 mg and morphine at 20, 30, 40, or 50 mg were dissolved by 2% acetate and dripped slowly into 15 ml soy-bean oil containing 0.75 ml Span80. After full emulsification at 35 degrees C; for 1.5 h, the mixture was dripped slowly into sodium tripolyphosphate (10 mg/ml) at the mass ratio of 5:1, 7:1, or 9:1 to allow cross-linking for 2 h. The drug loading, encapsulation efficiency and in vitro drug release of the preparations were measured. RESULTS: The drug loading in the microsphere increased while the encapsulation efficiency reduced with the increment of the initial morphine quantity. High cross-linking degree resulted in prolonged release time of the drug loaded in the preparations. CONCLUSION: The microspheres loaded with morphine allows sustained release of morphine.