Plasticizing effect of ibuprofen induced an alteration of drug released from Kollidon SR matrices produced by direct compression

The objectives of this study were to investigate the effect of storage temperature on drug release from matrices containing 10, 40 and 70% w/w ibuprofen in Kollidon® SR (KSR). The matrix tablets were produced by direct compression and then kept at 30 and 45 °C for 3 months. Drug release from the matrix tablets was examined after storage for 0, 1, 4 and 12 weeks. Scanning electron microscope was used to reveal physical appearance of the tablet surface at the respective time intervals. In addition, differential scanning calorimeter was used to investigate glass transition temperature (Tg) of ibuprofen in KSR at 0–100% w/w based on the principle of Gordon–Taylor equation. At 45 °C, the dissolution of ibuprofen in KSR as well as the coalescence of polymer particles were observed to be higher than those of storage at 30 °C. The physical state of ibuprofen dispersed in the polymeric matrix and degree of polymer coalescence led to the variation of drug release. The coalescence of polymer particles was a result of the polymer transition from glassy to rubbery state according to water absorption of KSR and plasticizing effect of ibuprofen. The reduction of the Tg of ibuprofen blended with KSR could be better described by the Kwei equation, a modified version of Gordon–Taylor equation.