SOLID-STATE INTERACTION OF IBUPROFEN WITH POLYVINYLPYRROLIDONE

We found that ibuprofen (IPF) became amorphous when the crystalline po wder was merely mixed with polyvinylpyrrolidone (PVP), using a test tu be mixer, and allowed to stand at appropriate temperatures, The crysta llinity of the mixture was evaluated from the X-ray diffraction spectr a by Ruland's method, The degree of decrease in crystallinity (A), def ined as the ratio of the decrease in crystallinity to the value calcul ated by assuming additivity of crystallinity, increased gradually with time for the IPF-PVP system, We found that the higher the storage tem perature, the higher the weight ratio of PVP in the mixture and the lo wer the molecular weight of PVP, the greater was the degree of decreas e in crystallinity. The effect of PVP particle size was observed in 1: 1 and 1:3 IPP/PVP mixtures. The interaction of IPP with PVP in the sol id state was investigated by IR and C-13-NMR analyses, and the molecul ar geometry of 1-ethyl-2-ppyrrolidone (EtP, a model compound for PVP) was calculated by the molecular orbital method (PM3), Our findings sug gested that EtP undergoes O-protonation, forming a hydrogen bond at th e carbonyl oxygen, in preference to N-protonation.