Effect of temperature on the tensile strength of lactose coated with fatty acids. Part 2. Tablets

Preparation and characterisation of a new insoluble polymorphic form of glibenclamide

A crystalline form of glibenclamide, with higher melting point (218 degrees C) and lower solubility in simulated gastric and intestinal fluids, was arisen during an attempt to elucidate transitional phases by melting, cooling and reheating. The new form was obtained from the glassy state, by applying sublimation at 130-160 degrees C and was characterised by differential scanning calorimetry (DSC), infrared (IR) spectroscopy, scanning electron microscopy (SEM), hot-stage microscopy (HSM), X-ray powder diffraction (XRD) and solubility studies. Formation of the new crystal form is considered as reason of reduction in dissolution and bioavailability of tablets.

The effect of temperature on the plasto-elasticity of some pharmaceutical powders and on the tensile strengths of their tablets

Measurements have been made of the stress relaxation (SR) during, and of the elastic recovery (ER) after, compression of four directly compressible excipients, and of chloroquine diphosphate and of a paracetamol tablet formulation at temperatures between -10 and +65 degrees C and of the tensile strengths of the tablets produced. It was found that at a fixed packing fraction, the stress relaxation and tensile strength of all the materials increased and the ratio ER/SR decreased as the compression temperature was raised. Tensile strength was inversely proportional to ER/SR at all the temperatures studied. Values for the activation energies (Eo) of bonding between particles for all the materials were derived from plots of the log of tensile strength and of log SR/ER versus the reciprocal of the absolute temperature. The values of Eo obtained from the latter plots tended to be higher than from the former by a factor of between 1.5 and 4.5.