Abstract
The characteristics of agglomerated crystals of enoxacin prepared by a spherical crystallization technique with the acetone-ammonia water-dichloromethane solvent system were investigated. Enoxacin forms a sesquihydrate, but has two different pseudopolymorphs, i.e. anhydrate and trihydrate. The crystalline form of the resultant agglomerates could be controlled by selecting the composition ratio of the three solvents and their mixing procedure. In order to obtain the sesquihydrous agglomerates, the mixing of an ammonia water solution of enoxacin with acetone in the first stage was required. When ammonia concentration in ammonia water used as a bridging liquid was higher, agglomerated crystals became smaller in size and less spherical in shape. The average size of agglomerates decreased with an increase in agitation speed and with a decrease in the ammonia water fraction in the solvent system. Primary crystals composing the agglomerates grew larger in size in the solvent system where the crystallization rate was reduced, resulting in less spherical agglomerates. Spherically agglomerated crystals prepared with a low fraction of ammonia water improved their flowability and packability without much delay in their dissolution rate, as compared with the primary crystals.
