Stress degradation studies of nelfinavir mesylate by Fourier transform infrared spectroscopy

Photostability testing using online reactor HPLC hyphenation and mass spectrometric compound identification illustrated by ketoprofen as model compound

Investigations on the photochemical stability of pharmaceutical substances are mandatory in drug development and licensing as photo-induced degradation of an active pharmaceutical ingredient (API) may not only lead to decreased API concentrations but also to toxic or reactive products. Thus, the US Food and Drug Administration (FDA) and the International Council for Harmonisation of Technical Requirements for Pharmaceuticals for Human Use (ICH) issued Guidance for Industry Q1B "Photostability Testing of New Drug Substances and Products" for testing of pure but also packed drugs. However, photoproducts are also known to be generated in vivo under sunlight exposure of the skin and lead to considerable amounts of adverse drug effects. Herein we present an alternative system that may be used for photostability testing mimicking both situations. It combines a tailored photoreactor with an exchangeable pen light source and a modified HPLC system with online-SPE. Identification of photoproducts may be performed using mass spectrometry. The potential of accurate mass spectrometry as a tool for identification of photoproducts was demonstrated as well. A comparison of the online photoreactor system and the traditional photochamber irradiation was performed using ketoprofen for proof of concept. In both designs acetylbenzophenone and ethylbenzophenone were detected as main photoproducts. The new device allows for fast and easy photostability studies that may help to reduce time consuming in vitro experiments and animal trials. Using state of the art instruments kinetic studies could also easily be performed with qualitative and quantitative perspectives combined into one experimental design with only very low amounts of API needed. This may be useful in early drug development, where only small amounts of API are available. Scale-up may also be easily realized for the generation of reference material for quantification and quality control (QC) processes as well as for toxicity testing.

Thermal stability and hydration behavior of ritonavir sulfate: A vibrational spectroscopic approach

Ritonavir sulfate is a protease inhibitor widely used in the treatment of acquired immunodeficiency syndrome. In order to elucidate the inherent stability and sensitivity characteristics of ritonavir sulfate, it was investigated under forced thermal and hydration stress conditions as recommended by the International Conference on Harmonization guidelines. In addition, competency of vibrational (infrared and Raman) spectroscopy was assessed to identify structural changes of the drug symbolizing its stress degradation. High performance liquid chromatography was used as a confirmatory technique for both thermal and hydration stress study, while thermogravimetric analysis/differential thermal analysis and atomic force microscopy substantiated the implementation of vibrational spectroscopy in this framework. The results exhibited high thermal stability of the drug as significant variations were observed in the diffuse reflectance infrared Fourier transform spectra only after the drug exposure to thermal radiations at 100 °C. Hydration behavior of ritonavir sulfate was evaluated using Raman spectroscopy and the value of critical relative humidity was found to be >67%. An important aspect of this study was to utilize vibrational spectroscopic technique to address stability issues of pharmacological molecules, not only for their processing in pharmaceutical industry, but also for predicting their shelf lives and suitable storage conditions.