AN INVESTIGATION INTO THE MELTING BEHAVIOR OF BINARY MIXES AND SOLID DISPERSIONS OF PARACETAMOL AND PEG-4000

The melting behavior of paracetamol and polyethylene glycol (PEG) 4000 , both individually and as binary systems, has been studied using diff erential scanning calorimetry. The appearance of the PEG peaks was sho wn to be highly dependent on scanning rate, with evidence for the exis tence of once-folded and extended chain forms being noted at slower sc anning speeds. The melting peak of paracetamol was found to be profoun dly influenced by the presence of the PEG 4000; when observed at all, the endotherm became broader and occurred at a lower temperature on mi xing with the polymer. The thermal behavior of the binary mixes was ag ain highly dependent on scanning rate, with faster rates leading to th e appearance of the paracetamol peak at lower concentrations. The mixe s were then thermally cycled to mimic production of solid dispersions, showing that the temperature cycling of the PEG 4000 could result in binary melting with the paracetamol peak disappearing. The interpretat ion of these results in terms of the characterization of PEG solid dis persions is discussed.