Evaluation Seminar On

Evaluation seminar on….. CRYSTALLINITY AND POLYMORPHISM CRYSTALLINITY AND POLYMORPHISM: Cryst al habit and inter nal struc ture of a drug can aec t bulk and physicochemical propertie s, which ranges from owability to chemi cal stability. Habit is the description of outer appearance of a crystal. Whereas the internal structure is the molec ul ar arrangement wi thin the sol id. Changes with internal structure usually alter crystal habit. Eg. Conversion of sodium salt to its free acid form produce both a change in internal structure and crystal habit. !epending on the internal structure a compound can be classi"ed as 1. Crystalline 2. Amorphous Crystals are characteri#ed by repetitious spacing of constituent atoms or molecules in a three dimensional arr ay . $n case of amo rphous for ms atoms or molecules are randomly placed as in a li%uid. &he amorphous for ms are usuall y of higher the rmodynami c energy than the crystalli ne form. 'pon storage, the amorphous forms tend to convert to more stable crystalline forms. (o due consideration should be given for these changes. Eg) &he amor ph ous fo rms of *ovobi oc in wa s found to be well absorbed, however when formulated into a suspension, convert into more stable crystalline form and results in poor absorption. + polymeric form may contain stiochiometric or non stiochiometric solvents. $f the solvent is water, the comple is called a hydrate. &he term hemihydra tes, monohydrate, dihydr ate etc describe hyd rate for ms with molar e%uivalence of water . + compound not containing a ny water molecule within its crystal structure is termed as anhydrous. +nhydrous forms are more soluble Conversion of anhydrous form to hydrous form within dosage form may reduce the dissolutio n rate and e tent of absorption. $denti "cat ion of possi bl e hydr ate compounds is important since thei r

Evaluation Seminar On

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