Stabilisation of metastable polymorphs: the case of paracetamol form III

The design of a melt synthesis of the first air-stable formulation of the metastable form III of paracetamol is derived from thermo-spectroscopic and thermo-diffraction experiments. Melt crystallisation in the presence of beta-1,4-saccharides produces form III selectively and the excipients appear to act as stabilising 'active' templates of the metastable polymorph.