Particle design of tolbutamide in the presence of soluble polymer or surfactant by the spherical crystallization technique: improvement of dissolution rate.

Poorly soluble crystals of tolbutamide were modified in the presence of a soluble polymer or surfactant by the spherical crystallization technique, the objective being to improve the dissolution rate and to transform platelet crystals into spherical agglomerates. An HCI solution was added to a tolbutamide:NaOH solution containing a water-soluble polymer or surfactant. The tolbutamide crystals were agglomerated with either and were free flowing and spherically compact. The size of the crystals of the agglomerate depended on the viscosity of the solvent and adsorption of the surfactant onto the crystal surface. The tolbutamide-agglomerated crystals dissolved isotropically, with no evidence of disintegration. The dissolution process was described in terms of the Hixson-Crowell equation. The dissolution rate of the agglomerate was 8 times faster than that of conventionally crystallized tolbutamide. Therefore, the solubility and flow-ability of tolbutamide can be improved using the spherical crystallization technique.