Transformation of chloramphenicol palmitate from therapeutically inactive polymorph A to active polymorph B
Identification and determination of modification A in modification B by DSC
The bioeffectivity of the therapeutically stable modification A of chloramphenicol palmitate is essentially less than that of the metastable modification B. The literature data indicate that the transformation of modification B to modification A is always monotropic. However, by means of cyclic heat treatment, the stable, inactive modification A has now been successfully transformed to the ‘metastable’, but pharmaceutically effective modification B. For identification and determination of the inactive polymorph A (as impurity) in the active polymorph B, DSC affords rapid and well-reproducible results on small samples. This method may be recommended for inclusion in pharmacopoeias.