Sustained Release of Phenytoin Following the Oral Administration of Phenytoin Sodium : Ethylcellulose Microcapsules in Human Subjects and Rabbits

Phenytoin sodium was microencapsulated with ethylcellulose (EC) by a coacervation-phase separation method from ethyl acetate solution to develop a prolonged release dosage form of phenytoin. Release of phenytoin from the microcapsules (phenytoin sodium/EC) was evaluated by the JP dissolution test in JP disintegration media No. 1 and No. 2. The release rates of phenytoin from phenytoin sodium powders were extremely rapid in both media, however, the release rates from the microcapsules were much more retarded. Following the oral administration of microcapsules to rabbits, prolonged plasma concentrations of phenytoin were obtained, while microcapsules orally administered to human subjects showed prolonged urinary excretion of phenytoin metabolites.