Selective recrystallization of metastable polymorph of melt acetaminophen by using tempering operation

•Tempering operation is applied to control of polymorphism in melt crystallization.•XRD–DSC experiments were carried out for thermodynamics analysis using onset temp.•The operating guideline for production of ACM metastable polymorph was proposed.

In organic melt crystallization, the control of polymorphism is important because of the bioavailability enhancement. In this present study, the methods for stable production of Acetaminophen (ACM) metastable polymorph are investigated in the tempering operation. The purpose is to obtain the operating guidelines for tempering operation for selective manufacturing technique of the polymorphic form. As the results, metastable form II was obtained with sufficient reproducibility under the condition of recrystallization during reheating stage. The operating conditions for crystallization of ACM metastable polymorph were determined by defining four requirements. The operating guidelines for production method of ACM metastable polymorph were proposed.

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