Preparation and in vitro dissolution tests of egg albumin microcapsules of nitrofurantoin

Abstract

Egg albumin microspheres of nitrofurantoin with and without ethylcellulose coating have been prepared by the methods of heat coagulation and phase separation. The effects of experimental conditions on the properties of beads and drug release rate were studied. In vitro dissolution tests in pH 7.2 phosphate buffer showed that release rate of nitrofurantoin from albumin beads was significantly reduced as compared to the nitrofurantoin powder. Ninety percent of the drug dissolved from the nitrofurantoin powder in about 1 h, while approximately 2 h were needed for half of the drug to be released from the albumin beads. The release of nitrofurantoin from ethylcellulose-coated microcapsules followed an apparent zero-order rate, although the drug was not completely released from the beads during the 8 h dissolution time. The constant rate of drug release from the coated beads suggests that the release of the drug was largely controlled by the permeability of nitrofurantoin through the coating.