STM Article Repository

The partitioning of two non-steroidal anti-inflammatory drugs (NSAIDs), flurbiprofen and ketoprofen, into cationic cetyltrimethylammonium micelles was investigated using semi-equilibrium dialysis at 37℃ in phosphate buffered saline. The micellar-water solubilization equilibrium constants for both NSAIDs, in their deprotonated forms, were observed to decrease linearly with increasing mole fraction of drug in micelles. For flurbiprofen, the solubilization constant in the limit as mole fraction of drug in micelles approaches zero was found to be 11,200 (co = 1 M), while for ketoprofen the value was 1950 (co = 1 M). Using 1H-NMR and UV spectroscopic techniques, the locus of solubilization for ketoprofen was found to be towards the charged exterior of the micelles, in the Stern layer, whereas flurbiprofen was found to solubilize more in the micellar interior.