A novel approach to crystallisation of nanodispersible microparticles by spray drying for improved tabletability.

High-dose API powders which are to be tableted by direct compression should have high compactibility and compressibility. This note reports on a novel approach to the manufacture of crystalline powders intended for direct compaction with improved compactibility and compressibility properties. The poorly compactable API, chlorothiazide, was spray dried from a water/acetone solvent mix producing additive-free nanocrystalline microparticles (NCMPs) of median particle size 3.5 μm. Tablets compacted from NCMPs had tensile strengths ranging from 0.5 to 4.6 MPa (compared to 0.6-0.9 MPa for tablets of micronised CTZ) at compression forces ranging from 6 kN to 13 kN. NCMP tablets also had high porosities (34-20%) and large specific surface areas (4.4-4.8m(2)/g). The time taken for tablets made of NCMPs to erode was not statistically longer (p>0.05) than for tablets made of micronised CTZ. Fragmentation of NCMPs on compression was observed. The volume fraction of particles below 1 μm present in the suspension recovered after erosion of NCMP tablets was 34.8±3.43%, while no nanosized particles were detected in the slurry after erosion of compacted micronised CTZ.