Structure Determination of Naproxen Photoproducts in the Tablet Generated by the UV Irradiation

Abstract

Change of the dosage form of the medicine is a useful method for the improvement of the medicine-taking compliance. However, the photostability of the medicine may be decreased on account of the change of the dosage form, followed by the change of the quality of it. On the other hand, there is few information focused on the photostability of the dosage-changed medicine. In this study, the effects of the change of the dosage form on the photostability of some non-steroidal anti-inflammatory drugs (NSAIDs) are investigated. Photo-exposure by means of the black light, containing ultraviolet (UV) at mainly 365 nm, induced the change of the color of naproxen tablets although the content of the active compound monitored by the high-performance liquid chromatography (HPLC) was not changed. However, the change of the dosage form of naproxen tablets to the powder and the suspension induced the change of the photostability followed by the decrease of the content of the active compound and the generation of two photoproducts. By means of the nuclear magnetic resonance (NMR) analysis, structures of two naproxen photoproducts were determined as 2-acetyl-6-methoxy-naphthalene and 1-(6-methoxy-2-naphthyl) ethanol. This is the first report evaluated the generation of naproxen photoproducts induced by the long-wavelength UV irradiation in the formulation.