Pharmaceutical inventions are increasingly focusing on delivery systems which enhance desirable therapeutic objectives while minimizing side effects. Recent trends indicate that multiparticulate drug delivery systems are especially suitable for achieving sustained release with low risk of dose dumping. In present investigation hollow microspheres (Microbaloons) were developed as a dosage form. Microballoons were prepared by the emulsion solvent diffusion method using ethyl cellulose with drug in a mixture of dichloromethane and ethanol. Preliminary studies revealed that the concentration of polymer and stirring speed significantly affected the characteristics of microballoons. It was found that temperature is an important factor which determined the formation of cavity inside the microspheres. The effect of process variables such as: polymer concentration and stirring rate were evaluated on the yield, particle size, Entrapment efficacy, floating behaviors and drug release of microspheres using a 32 factorial design. The optimum batch of microsphere exhibited good flow property, sustained drug release, remained buoyant for more than 8 hrs, entrapment efficiency up to 76 %w/w. SEM confirmed the hollow structure of microsphere. The results of 32 full factorial design revealed that the concentration of ethylcellulose (X1) and stirring speed (X2) significantly affected drug entrapment efficiency, percentage release after 8 h and particle size of microspheres.
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