Liquisolid

In the last decade, poorly soluble drugs have been an area of concern for all the researchers in the field of pharmacy. A number of researches have been carried out to enhance the solubility and dissolution properties of such drugs. This study deals with a comprehensive review of liquisolid technique carried out mainly for biopharmaceutical classification system (BCS) class II & IV drugs. These drugs are having problems of poor solubility, dissolution and thus poor bioavailability. Various studies conducted on a number of drugs so far, have been reviewed. A variety of techniques such as micronization, salt formation, complexation, solid solutions, and liquisolid technique etc. have been used to overcome such problems. It has been observed that liquisolid technique is the most promising way for solubility and dissolution enhancement of such drugs. It can be concluded that liquisolid technique results in increased solubility, dissolution and thus bioavailability.

In the present study Liquisolid preparations of nifedipine were prepared by dissolving the drug in a chosen non-toxic, non-volatile solvent and adsorbing onto carrier materials. Various carrier and coating materials were employed in the study. Avicel PH 101 was used as the carrier material and Aerosil was used as the coating material as conventional liquisolid systems, apart from that novel excipients like Fujicalin® and Neusilin® were employed and their effects on the dissolution rate of the drug was studied. The results showed that the solubility of the drug was maximum in polysorbate 20 amongst the selected non volatile solvents i.e. Polyethylene glycol 400, 600, propylene glycol, glycerol and Tween 20. The solution of nifedipine in polysorbate 20 was found to be stable for at least 15 days. It was also found out that Fujicalin® and Neusilin® were much better adsorbents as compared to microcrystalline cellulose. Fujicalin® enhanced the drug release where as Neusilin® when used as an adsorbent retarded the rate of release. Liquisolid systems in general showed enhanced dissolution profile as compared to their directly compressed counterparts. The prepared liquisolid systems were subjected to tests such as FT-IR spectroscopy, differential scanning calorimetry (DSC) and X-Ray crystallography (PXRD) for evaluating the physiochemical properties of the drug in the liquisolid systems. Differential scanning calorimetry and X-Ray crystallography conclusively proved the loss of crystalline structure of nifedipine in the liquisolid systems, thus confirming the enhanced solubility. The optimized liquisolid compact was then compared with commercially available soft gelatine capsules.