THERMAL-BEHAVIOR AND PHYSICOCHEMICAL PROPERTIES OF NAPROXEN IN MIXTURES WITH POLYVINYLPYRROLIDONE

The thermal behaviour (DSC, TGA) of naproxen (NAP) and various grades of polyvinylpyrrolidone (PVP; Mr almost-equal-to 10000, 25000, 40000 and 360000), and their mixtures was investigated. A profound modification of the NAP melting peak, observed in the DSC curves of simply blended systems (physical mixtures) with PVP, was attributed to a solid-state interaction. This interaction proved to be influenced by the composition of the mixture, the PVP average molecular weight and the type of manipulation of the sample (grinding, compaction, heating). The high dispersion of NAP within the PVP matrix probably gives rise to the formation of crystalline drug microaggregates (molecular clusters) responsible for the thermal behaviour. The chemical and physical stability (dissolution rate, crystallinity) of NAP was not significantly affected in the mixtures with PVP.