Advantages of celecoxib nanosuspension formulation and transformation into tablets

Drugs with low aqueous solubility and high permeability (BCS class II) present a high proportion of all drugs. This study examines the critical issues regarding engineering of a nanosuspension tailored to increase drug dissolution rate and its transformation into dry powder suitable for tabletting. Nanosuspensions of celecoxib, a selective COX-2 inhibitor with low water solubility, were produced by the emulsion-diffusion method using three different stabilizers (Tween® 80, PVP K-30 and SDS) and characterized by particle size analysis, dissolution testing, scanning electron microscopy imaging, differential scanning calorimetry and X-ray powder diffraction. Spray-dried nanosuspension was blended with microcrystalline cellulose, and compressed to tablets, and their tensile strength, porosity and elastic recovery of tablets were investigated. The selection of solvent and stabilizers is critical, firstly to achieve controlled crystallization and size, and secondly to increase the wettability of the hydrophobic drug. The crystalline nano-sized celecoxib alone or in tablets showed a dramatic increase of dissolution rate and extent compared to micronized. SEM images showed that the nanoparticle morphology was influenced by the choice of stabilizers. Celecoxib nanosuspension stabilized with PVP K-30 and SDS showed advantages over Tween® 80 due to sticking of the dried product and unexpected changes observed on DSC curves. Markedly lower compaction forces are needed for nano-sized compared to micro-sized celecoxib to produce tablets of equal tensile strength.