Enhancement of dissolution behavior of antiarthritic drug leflunomide using solid dispersion methods

Novel pharmaceutical formulations of antiarthritic drug leflunomide (LEF) with polyvinylpyrrolidone (PVP), polyethylene glycol (PEG) and hydroxypropylmethylcellulose (HPMC) were developed with the aim to improve the LEF dissolution behavior. Solid dispersions were prepared by grinding, freeze-drying and kneading methods and characterized using DSC, XRPD and FTIR spectroscopy. All the investigated polymers were effective in improving the LEF dissolution behavior. Significant increase of the dissolution rate of LEF in its solid dispersions with PVP and PEG was explained by the reduced crystallinity of the drug and solubilizing action of these polymers. An essentially lower dissolution rate of LEF/HPMC solid dispersions was attributed to higher viscosity of dissolution medium due to the presence of HPMC. The results showed that LEF/PVP solid dispersions can be considered as immediate release dosage forms, while LEF/HPMC solid dispersions ban be proposed as a sustained release product for the case when the moderation of drug release is required.