Compatibility study of tretinoin with several pharmaceutical excipients by thermal and non-thermal techniques

Thermal techniques, such as differential scanning calorimetry, thermogravimetry (TG), derivate of TG curve (DTG), and differential thermal analysis were used as quick screening tools to evaluate the possible interactions between tretinoin (TRET) and excipients used in semi-solid pharmaceutical forms. The non-thermal techniques, fourier transform infrared (FTIR) spectroscopy, X-ray diffractometry (XRD), and scanning electron microscopy (SEM) were used as a supplementary investigative techniques of possible interactions. The analysis of the FTIR spectra of TRET/excipient binary mixture (BM) was also conducted by a method of Pearson’s correlation, which calculated the difference between the theoretical and experimental FTIR spectra. The TRET, excipients and BM were heated at 200 °C to be analyzed by FTIR and XRD. The physical interactions suggested were mainly observed in the results obtained by thermal techniques with TRET/MTP, TRET/PPP, TRET/CA, and TRET/CTA, but in the TRET/IMD, the FTIR technique shows that there was chemical interaction between these components. The heating of samples changed the chemical structure of the TRET in the TRET/CTA, as well as changed the crystallinity of the TRET in the TRET/MTP and TRET/PPP BM. SEM microphotograph of the mixtures showed no adhesive interfaces in mixtures suggesting that no intense physical interactions between these pharmaceutical raw materials at room temperature.