Solid state interaction between amoxicillin trihydrate and potassium clavulanate

The aim of this research was to evaluate solid state interaction between amoxicillin trihydrate and potassium clavulanate. The interaction was observed by Differential Scanning Calorimeter (DSC), X-Ray Powder Diffractometer (XRPD), Fourier Transforms Infra Red (FTIR) and Scanning Electron Microscope (SEM). Mixtures of amoxicillin trihydrate and potassium clavulanate were prepared in molar ratios of 0:10, 1:9, 2:8, 3:7, 4:6; 5:5; 6:4; 7:3; 8:2; 9:1; 10:0 and analyzed by DSC to obtain the thermal profile and a phase diagram. From this phase diagram, the molar ratio point of interaction was determined. XRPD analysis was performed to check the type of physical interaction occurred and FTIR was conducted to predict the chemical mechanism of interaction. Thermo profile obtained by DSC analysis of the binary systems showed that endothermic curves of molar fractions of 1:9—5:5 overlapped at 201°C. On the other hand, the diffractogram obtained from Powder X-Ray analysis was very similar with that of amoxicillin trihydrate alone. FTIR spectrum of binary system in the molar ratio of 5:5 showed the loss of hydrate spectra from amoxicillin trihydrate. We conclude that the interaction involved strong hydrogen bonding between hydrates of amoxicillin with potassium clavulanate which produced a co-crystal system like a solid dispersion.