Effect of binary and ternary polyvinylpyrrolidone and/or hydroxypropyl-beta-cyclodextrin complexes on the photochemical and photosensitizing properties of Naproxen.

The effect of the polyvinylpyrrolidone and/or hydroxypropyl-beta-cyclodextrin on the photo-lability of aqueous solutions of the anti-inflammatory drug Naproxen was studied. Kinetic studies revealed that the presence of all of these additives reduced drug photodegradation. In all cases, the presence of the different additives elicited a change in the photomixture composition, being the alcoholic derivative the major photoproduct formed. Nevertheless, the change in the efficiency of the process and the amount of the photoproducts formed in the different systems were not related with the biodamage produced by the drug. In this sense, the presence of free Naproxen clearly sensitized the photoperoxidation of linoleic acid. The photosensitizing effect decreased as the PVP concentration increased. Different protection provides the binary (Naproxen:HP-beta-CD) and ternary (Naproxen:HP-beta-CD:PVP) complexes. The binary complex formation had not effect on the prevention of photooxidation of linoleic acid sensitized by the drug, whereas the ternary complex formation suppresses the drug effect. The different behaviour observed with beta-CD and HP-beta-CD and the structural differences of both cyclodextrins seem to indicate that in the case of the HP-beta-CD the linoleic binds with the CD and takes contact with the drug. These results confirm that in these systems the prevention of biodamage would be due to a decrease in the contact between the short-lived species generated during Naproxen photodegradation and biological structures, rather than due to the nature or amount of the photoproducts. In addition, the ability of the complex to interact with the biological structure depends on the structure of both interacting species.