The interconversion of the polymorphic forms of chloramphenicol palmitate (CAP) as a function of environmental temperature

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Abstract
When polymorph B of chloramphenicol palmitate (CAP) is heated at 82 °C for 1600 minutes it changes completely to the less soluble and less bioavailable polymorph A. When polymorph C, the most soluble polymorph, is grinded for a prolonged period it changes to polymorph A through B. We investigated the effect of the environmental temperature on the interconversion of polymorph C. This was done to determine the effect that heat generated during grinding could have on polymorph C. Samples of polymorph C was kept at 50 and 75 °C respectively. At predetermined intervals samples were withdrawn and differential scanning colorimetric (DSC) curves and Xray powder diffractograms recorded. Both samples changed to polymorph B but only the sample kept at 75 °C changed into A during the time the experiment was run. Therefore temperature control during storage and handling, especially grinding, of polymorph C and B is recommended to prevent conversion to the poorly soluble and less bioavailable polymorph A.