An extensive compatibility study of mycophenolate mofetil with different excipients by spectroscopic and thermoanalytical investigation techniques

Mycophenolate mofetil is used as an immunosuppressive agent to prevent acute rejection of transplanted organs. Mycophenolate mofetil is rapidly absorbed following oral administration and hydrolysed by esterases in the liver and kidney to its active metabolite, mycophenolic acid, a selective and reversible inhibitor of inosine monophosphate dehydrogenase. Due to the clinical advantages of mycophenolate mofetil, there has been an increase in the number of mycophenolate mofetil formulations in the market in recent years. This study aims to investigate the compatibility of mycophenolate mofetil with several excipients frequently used in drug formulations, hence a robust analysis of thermal-induced events on the pharmaceutical active agent and its binary mixtures. To evaluate the thermal behaviour of mycophenolate mofetil–excipient mixtures, TG-DSC curves were recorded from 40 to 500 °C in dynamic air flow. The study was also conducted in nitrogen atmosphere by DSC analysis, using a temperature programme from 40 to 350 °C. Compatibility studies performed by TG-DSC analysis showed some peak shifts in the TG curve and DSC curve, hence a supposition that interactions could occur. The DSC curve recorded for the same mixture does not behave as a sum of the DSC curves of the pure compounds. This behaviour is put into the account of a thermally induced interaction between the pharmaceutical active agent and some of the excipients used in this study.