pH-sensitive release of indomethacin using lactan-acetate microspheres.

Hydrophobic lactan acetate was prepared from hydrophilic lactan gum by chemical modification and it was used for a pH-sensitive drug delivery system. Lactan acetate microspheres were prepared by the solvent evaporation method. The size of the microspheres prepared from lactan acetate was below 5 microns. The drug loading efficiencies of microspheres were approximately 70 and 80% at the initial amount of drug 40 and 80 mg, respectively. The microsphere showed pH-sensitive swelling behavior. The swelling capacity of microspheres at pH 7.4 was much greater than that at pH 1.2. The pH of the medium significantly influenced the in vitro release rate; the rate at pH 7.2 was approximately 10 times faster than that at pH 1.2. A pH-sensitive drug release pattern was due to the escape of drug from the microsphere that disintegrated after swelling.