A Review on Precipitation inhibitors in supersaturable self emulsifying drug delivery system

Abstract

The super saturable formulation has been widely used as an effective method to improve solubility and oral absorption of poorly aqueous-soluble drugs. When the super saturable formulation comes in contact with gastrointestinal fluids, its drug concentration goes over the equilibrium solubility, but this state does not exist for too long, the drug may precipitate before being absorbed, which minimizes the efficacy and bioavailability of the drug. Therefore, it is necessary to inhibit or retard the precipitation of drugs to achieve the maximum benefits of the super saturable formulation. Polymers (watersoluble and insoluble) are the commonly used excipients to inhibit precipitation. Cyclodextrins and surfactants are the other two excipients used as precipitation inhibitors. In some of the cases, even solid carriers can effectively retard precipitation. The precipitation inhibitors (PI) have the capacity to maintain a super saturable state of the formulation in GI for a particular time period. Therefore, it is important to properly select the precipitation inhibitor; too frequently used methods to select precipitation inhibitor are casting film method and solvent-shift method. Such selected and successfully used precipitation inhibitors are HPMC E5LV, PVP K17, HPMC E5, soluplus, poloxamer 407, HPMCAS, maltodextrin (mal) and microcrystalline cellulose (mcc). Since the super saturable technique has been widely used for delivering poorly water-soluble drugs like ezetimibe, indirubin, feno fibrate, butyl paraben and rosu vastatin calcium. There is a necessity for bio relevant evaluation of supersaturation/precipitation because simple methods like dissolution tests cannot be bio relevant in a supersaturation/precipitation context. Some of the important factors like sink versus non-sink conditions, hydrodynamic, medium selection and temperature play a vital role in the evaluation of in-vitro supersaturation