Preparation and characteristics of microcapsules containing enoxacin by one continuous process of agglomeration and...

A novel microencapsulation technique was carried out with the phase separation of Eudragit RS from the wet spherical agglomeration (WSA) system by non-solvent addition. To elucidate the characteristics of microcapsules the spherical agglomerates containing enoxacin (ENX), lactose or Avicel which are different in their affinity to water (i.e. insoluble, soluble or absorbable properties, respectively), were prepared as core particles in an acetone/n-hexane mixture (volume ratio 3/7) by a WSA technique. The size of all kinds of spherical agglomerates was controlled by the amount of bridging liquid (ammonia water or distilled water) used. In the microencapsulation process encapsulation was performed efficiently at 400-600 rpm. Avicel agglomerates could be coated up to 30 per cent with Eudragit RS with less aggregation. Various additives were compared as additions into the system to avoid the aggregation of encapsulated particles. Addition of more than 3 per cent magnesium stearate based on the core weight in the system, before or at the same time as phase separation of Eudragit RS occurred, resulted in low aggregation of microcapsules for spherical agglomerates containing ENX or lactose. In formulating a water-absorbable excipient such as Avicel in the agglomerates of ENX, adding some 10 per cent Eudragit RS-dichloromethane solution into the WSA system, and using magnesium stearate as a protective agent, the resultant microcapsules could be obtained efficiently without aggregation, showing sustained release of ENX depending on coating level.