Pharmaceutical polymorphism: The phenomenon affecting the performance of drug and an approach to enhance drug solubility, stability and bioavailability
Pharmaceutical solids can exist in different physical forms. Polymorphism is often characterized as the ability of a drug substance to exist two or more crystalline phases that have different arrangements and conformations of the molecules in the crystal lattice. In past decades, there have been significant efforts on the discovery, selection and control of the solid forms of active pharmaceutical ingredients and bulk drugs. Polymorphs and solvates of a pharmaceutical solid can have different chemical and physical properties such as melting point, chemical reactivity, apparent solubility, dissolution rate, optical and electrical properties, vapour pressure, and density. Polymorphism must be controlled to prevent possible ineffective therapy and improper dosage. Drugs with low water solubility are predisposed to poor and variable oral bioavailability and, therefore, to variability in clinical response, that might be overcome through an appropriate formulation of the drug. Polymorphs (anhydrous and solvate/hydrate forms) may resolve these bioavailability problems Number of strategies exists for enhancing the bioavailability of those drugs, these strategies are greatly dependent on the physical and chemical nature of the molecules being developed. This review will discuss the applied nature of polymorphism starting from their preparation, characterization and pharmaceutical importance with a special emphasis on drug.
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