 Stoichiometric ratios of 1:1, 1:2, 1:3, 2:1 and 3:1 of Febuxostat and the coformer (probenecid, adipic acid and α-ketoglutaric acid) respectively, were subjected to a liquid assisted grinding (LAG) approach, with the drop wise addition of acetonitrile (25µL) in a mortar and pestle.  The ground mixture was then dried in an oven at 80 ºC for 2 hours. Post drying, it was transferred into a dry container and kept in the desiccator.  The solid-state characterization of FXT and its eutectic systems was carried out using a differential scanning calorimeter (DSC) and powder X-ray diffraction (PXRD). The DSC results were in turn used to construct the binary phase diagram (BPD) for each system.  pH dependent solubility studies were carried out at 25 ºC using the shake flask method over a pH range of 4-10 using different buffered solutions.  And the micro-environmental pH studies were performed using the slurry method. Poster No. 21M1200 Febuxostat Eutectics: lost moieties in the quest for Co-crystals Moksh Jagia1, Ruchi Daptardar1, Kinjal R Patel1, Sameer Modi2, Pawan Kumar Singh2, Arvind Kumar Bansal2, Sarsvatkumar Patel1 1Arnold and Marie Schwartz College of Pharmacy and Health Sciences, Long Island University, NY 2National Institute of Pharmaceutical Education and Research (NIPER), India PURPOSE METHOD RESULTS & DISCUSSION Screening, preparation and characterization of eutectic systems of the drug Febuxostat (FXT), using thermal and analytical techniques, with the initial goal of screening for co- crystals. CONCLUSION REFERENCE  DSC indicated towards the formation of eutectic systems by the presence of an invariant low melting endotherm in each case.  PXRD confirmed the systems as eutectic with combination peaks of drug and coformer  The presence of an acidic micro-environment imparted by the coformers resulted in a substantial loss of eutectic system solubility.  Further cocrystallization studies with better coformer selection strategy for the weakly acidic FXT drug needs to be carried out.  S. Cherukuvada, A Nangia, “Eutectics as improved pharmaceutical materials: design, properties and characterization,” Chem. Commun. 2014, 50, 906.  Badawy, Sherif I. Farag, and Munir A. Hussain. "Microenvironmental pH modulation in solid dosage forms." Journal of pharmaceutical sciences 96.5 (2007): 948-959.  A single invariant low melting point (solidus) in all molar compositions is the characteristic of the eutectic phase.  While a small variable liquidus point manifests for the near- eutectic or non-eutectic compositions  A typical BPD of a eutectic assumes a ‘U” or ‘V’ shape, with the point lacking the liquidus peak representing the pure eutectic phase.  While the BPD of a co-crystal assumes a ‘W’ shape. 160 170 180 190 200 210 220 160 170 180 190 200 210 220 0 0.25 0.5 0.75 1 Temperature (°C) Mole Fraction of FXT Solidus Peak Liquidus Peak FXT PROB FXT:PROB Eutectic 130 140 150 160 170 180 190 200 210 220 130 140 150 160 170 180 190 200 210 220 0 0.25 0.5 0.75 1 Temperature (°C) Mole Fraction of FXT Solidus Peak Liquidus Peak FXT ADP FXT:ADP Eutectic 90 110 130 150 170 190 210 90 110 130 150 170 190 210 0 0.25 0.5 0.75 1 Temperature (°C) Mole Fraction of FXT Solidus peak Liquidus peak FXT a-KETO FXT: a-KETO Eutectic 0 2000 4000 6000 8000 10000 12000 14000 4.01 5.63 8.21 10.13 Solubility (µg/mL) pH FXT Drug FXT:Probenecid (1-1) Eutectic FXT:Adipic acid (1-3) Eutectic FXT:a-Ketoglutaric acid (1-3) Eutectic The invariant endotherm for FXT:PROB system appeared around 174ºC, with the single phase melting transition (1-1 ratio) at 175.23 ºC representing the pure eutectic phase. The BPD exhibited a ‘U’ shape characteristic for eutectic formation. The invariant endotherm for FXT:ADP system appeared around 149ºC, with the single phase melting transition (1-3 ratio) at 150.23ºC representing the pure eutectic phase. The BPD exhibited a ‘V’ shape characteristic for eutectic formation. The invariant endotherm for FXT: a-Keto system appear