Characterisation of polyethylene glycol solid dispersions using differential scanning calorimetry and solution calorimetry

Abstract

Solid dispersions of nortriptyline HCl in a range of molecular weight PEG samples were manufactured using a low temperature fusion method, whereby the drug remained intact within the dispersion. The phase diagrams obtained using differential scanning calorimetry were monotectic in nature, suggesting that these diagrams represent systems whereby little or no interaction is present between the solid components. Electron micrographs also showed the drug particles to remain largely intact following the fusion process. Studies using solution calorimetry indicated that the heats of solution of the binary systems were lower than theoretically predicted, indicating an interaction between the two components during the dissolution process.