Solid state of aceclofenac: characterization, transformation

The objective of this work was to investigate the existence of polymorphs and pseudopolymorphs of aceclofenac which is a peripherally acting, non-steroidal anti-inflammatory analgesic with anti-inflammatory, antiarthritic and antipyretic activities. Three crystal forms of aceclofenac have been isolated by recrystallization and characterized by differential scanning calorimetry (DSC), powder X-ray diffractometry (PXRD) and thermogravimetric analysis. The DSC and PXRD patterns of the three crystal forms of aceclofenac were different respectively. After storage of 1 month at 0 % RH (silica gel, 20 °C), 52 % RH (saturated solution of Na2Cr2O7·2H2O/20 °C) and 95 % RH (saturated solution of Na2HPO4/20 °C), Form 1 and Form 3 (from methylethyl ketone) were not transformed, but Form 2 (from DMSO) was transformed to Form 1 at 95 % RH.