Effect of tabletting on the degree of crystallinity and on the dehydration and decomposition points of cephalexin crystalline powder.

Changes in the degree of crystallinity and in the dehydration and decomposition points of cephalexin (CEX) crystalline powder caused by tabletting were studied by means of X-ray diffraction analysis, infrared (IR) spectroscopy and differential thermal analysis (DTA). The degree of crystallinity of the compressed phase IV CEX was determined by the X-ray diffraction and IR-spectral methods, and the results agreed reasonably well. The maximum compression stress (MP) and the compression loss energy (LE) of phase IV CEX powder during tabletting compression were measured during compression in a single-punch tabletting machine. The degree of crystallinity of the compressed phase IV CEX decreased with increasing values of MP and LE, and was about 40% at LE=1.75 kcal/mol. The dehydration and decomposition points of the compressed phase IV CEX fell with decreasing degree of crystallinity. The plot of log (LE) against the degree of crystallinity showed a good straight line. The value of LE estimated by extrapolating the plot to zero crystallinity was 14.0 kcal/mol.