Structure Determination of Felodipine Photoproducts in UV-Irradiated Medicines Using ESI-LC/MS/MS

Assessment of Directional-Hemispherical Reflectance of Tablets with Cefuroxime during Storage under Elevated Temperature and Ultraviolet Radiation

Environmental conditions can lead to changes in the physical and chemical structures of drug products. In this study, the stability of cefuroxime tablets stored under adverse conditions was evaluated based on total directional-hemispherical reflectance (THR). The THR value was measured before and after the tablets' exposure to stress factors (temperature of 45 °C and UV radiation). Each measurement was performed three times within seven spectral bands at the beginning of the experiment (day 0), and then on days 1, 2, 3, 5, and 7. In addition, hyperspectral profiles (400-1030 nm) were analyzed on days 0 and 7. A significant decrease in THR values in all wavelength ranges was observed when day 7 vs. day 0 were compared, especially for spectral bands of 335-380 nm and 1700-2500 nm (Δ = 0.220, p < 0.001 and Δ = 0.171, p < 0.001, respectively). The hyperspectral analysis confirmed a decrease in the reflectance after the end of stress conditions in the visible light range (400-700 nm) compared to tablets before the experiment. This may indicate that more radiation entered the tablets. In conclusion, the THR of cefuroxime tablets decreases during the exposure to heat and UV radiation, which may result from some physicochemical changes that have occurred during storage.

Photodegradation profiling of nitrendipine: evaluation of active pharmaceutical ingredient, tablets and its altered forms

Nitrendipine (NTR) is a dihydropyridine drug, which is well-known as a photodegradable pharmaceutical. However, the photochemical reaction of NTR has not been evaluated in detail from now. In this study, we perform the photodegradation profiling of NTR for the elucidation of its photochemical behavior. NTR amounts during ultraviolet light (UV) irradiation were monitored using high performance liquid chromatography (HPLC). NTR was photodegraded almost completely within 24 h along with the generation of some photoproducts. Structural determination of two NTR photoproducts were carried out by means of electrospray ionization liquid chromatography tandem mass spectrometry (LC-ESI-MS/MS). Obtained results from this study clarified one novel NTR photoproduct, a nitroso pyridine analogue, in addition to a pyridine analogue. Furthermore, photodegradation pathway of NTR was speculated based on chemical structures of NTR photoproducts to clarify its photochemical behavior. It was proposed that a singlet oxygen molecule might withdraw two hydrogen radicals resulting in the form of a pyridine analogue, and the following reduction of its nitro group might produce a nitroso pyridine analogue. Finally, we evaluated the photostability of NTR tablets and its altered forms, indicating that the change of the dosage form led to a decrease of the photostability of NTR tablets. The obtained results will be helpful for the additional research to evaluate the effect of NTR photodegradation on its own biological activities.