Liquisolid technique for dissolution rate enhancement of a high dose water-insoluble drug (carbamazepine)

Different liquisolid formulations of carbamazepine were accomplished by dissolving the drug in the non-toxic hydrophilic liquids, and adsorbing the solution onto the surface of silica. In order to reduce the amounts of carrier and aerosil in liquisolid formulations, some additives namely polyvinylpyrrolidone (PVP), hydroxypropyle methylcellulose (HPMC) and polyethylene glycol (PEG 35000) were added to liquid medication to increase loading factor. The effects of various ratios of carrier to coating material, PVP concentration, effect of aging and type of the carrier on dissolution rate of liquisolid compacts were studied. X-ray crystallography and differential scanning calorimetery (DSC) were used for evaluation of physicochemical properties of carbamazepine in liquisolid formulations. The results showed that the drug loading factor was increased significantly in the presence of additives. Liquisolid formulations containing PVP as additive, exhibited significantly higher drug dissolution rates compared to the compacts prepared by the direct compression technique. It was shown that microcrystalline cellulose had more liquid retention potential in comparison with lactose, and the formulations containing microcrystalline cellulose as carrier, showed higher dissolution rate. By decreasing the ratio of microcrystalline cellulose to silica from 20 to 10, an improvement in dissolution rate was observed. Further decrease in the ratio of microcrystalline cellulose: silica from 10 to 5 resulted in a significant reduction in dissolution rate. Increasing of PVP concentration in liquid medication caused a dramatic increase in dissolution rate at first 30 min. The results showed that the dissolution rate of liquisolid tablets was not significantly affected by storing the tablets at 25 degrees C/75% relative humidity for a period of 6 months. The results of DSC and X-ray crystallography did not show any changes in crystallinity of the drug and interaction between carbamazepine and exipients during the process. (c) 2007 Elsevier B.V. All rights reserved.