The preparation and characterization of ethyl cellulose-walled theophylline microcapsules

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Abstract
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.