Acitretin is a second-generation retinoid and a metabolite of etretinate. While effective for severe psoriasis, its physical properties are highly dependent on the crystallization process. Because different crystalline structures (polymorphs) can change the drug’s solubility and shelf-life, precise characterization is essential for regulatory compliance and patient safety ( ResearchGate ). 2. Characterization of Polymorphic Forms
The stability of these forms is sensitive to temperature and pressure:
: Form I can be quantitatively converted into Form II.
: Exhibits a unique "catameric" arrangement where carboxylic residues form one-dimensional hydrogen-bonded chains, winding around a short monoclinic axis. 3. Thermal Stability and Phase Conversion
: This conversion occurs through moderate heating (approximately 200 °C ) under vacuum.