Crystal structures and properties of two new pseudopolymorphic modifications of the glucocorticoide triamcinolone diacetate

Two new solvates of triamcinolone diacetate were found in addition, to those reported previously. The acetonitrile solvate (form E) crystallizes monoclinic in space group P21, whereas the methylene chloride solvate (form F) crystallizes orthorhombic in space group P212121. In all forms the triamcinolone diacetate molecules are linked by intermolecular hydrogen bonding. From this arrangement channels are formed in which the solvent molecules are embedded. Both forms were investigated by differential thermoanalysis and thermogravimetry. On heating, for each form a mass loss is observed, which is accompanied with endothermic events in the DTA curve. Mass spectroscopic investigations clearly shows that in this step the solvent molecules are emitted. In these measurements one cannot differ between desolvation and melting. If the residues formed after the first TG steps are investigated by X-ray powder diffraction, only amorphous samples are obtained. If the solvents are removed at room temperature under normal pressure or in vacuum the commercial available form of triamcinolone diacetate is obtained which is also used in therapy. If the acetonitrile solvate is tempered at 80 °C for several days significant changes in the powder pattern are observed, which may indicate the formation of a new polymorphic form.

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