Thermal studies of furosemide–caffeine binary system that forms a cocrystal

Abstract

Thermal techniques, differential scanning cal- orimetry (DSC), and hot stage microscopy (HSM) have been used to study the interactions between furosemide and caffeine that are known to form a 1:1 cocrystal. This sys- tem has been used as an example to study the probable mechanism of cocrystal formation when the individual components, which are polymorphic, are heated. The study indicates that the phase transition of the low temperature stable polymorph of furosemide initiates cocrystal forma- tion. This result suggests increased mass transfer rate can trigger cocrystal formation. The binary phase diagram (composition-temperature plots) of furosemide-cocrystal- caffeine system was determined from the DSC curves. The results imply that the cocrystal forms eutectic with caffeine but not with furosemide. This study has thus exemplified the use of DSC in understanding binary phase system where the two components form a cocrystal.