The preparation and characterization of ethylcellulose-walled theophylline microcapsules.

The use of sustained-release preparations of theophylline has become routine in the treatment of bronchial asthma. Microencapsulation provides a possible means of producing such a product. The present paper examines, by means of triangular diagrams, the phases present in the system ethylcellulose-petroleum ether-toluene. The separated cellulose was used to coat the drug theophylline. The effects of temperature, petroleum ether fraction, solvent:non-solvent ratio and rate of non-solvent addition on the size and size distribution of the microcapsules was studied.