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Polymorphism Screening - Articles and news items

Figure 1 Packing diagrams showing the different molecular arrangements in polymorphs A (left) and B (right) of the antipsychotic drug risperidone (centre). Unit cell parameters for each polymorph are shown.

Polymorph screening in pharmaceutical development

Issue 4 2010, Screening / 19 August 2010 / Professor Alastair J. Florence, Solid-State Research Group, Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde

The majority of active pharmaceutical ingredients (APIs) are produced by crystallisation and so the phenomenon of polymorphism, whereby an organic molecule can adopt more than one crystalline form (Figure 1 opposite), is of considerable importance when trying to achieve consistent product quality during the manufacture of pharmaceutical solids and solid dosage forms. Although morphology and particle size-distribution are important solid-state characteristics, the uncontrolled occurrence of multiple physical forms (polymorphs, solvates, salts, co-crystals or amorphous) of an API can have significant effects on the performance of the material during processing, manufacture, storage and administration. For example, the solubility difference between some polymorphs has been shown to be over four times that of the least soluble form1 and can vary by significantly more for amorphous forms2.


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