Forced Degradation Study of Atazanavir, Emtricitabine, Nirmatrelvir, Oseltamivir, Ribavirin and Sofosbuvir

Antivirals are considered emerging environmental contaminants. Unfortunately, for many of these substances, there is limited information on their occurrence, fate, and behavior in the environment, which is essential for proper risk assessment. In this study, forced degradation tests were conducted on six widely used antivirals to assess their environmental fate. These antivirals were atazanavir, emtricitabine, nirmatrelvir, oseltamivir, ribavirin, and sofosbuvir. The tests included exposure of the antivirals to (artificial) sunlight, different temperatures, water, an acidic solution (1 M HCl), an alkaline solution (1 M NaOH) and a solution containing 30% H2O2 as a strong oxidizing agent. Liquid chromatography with UV detection (LC-UV) was used to analyze antivirals. To monitor the conversion, an LC-UV method was developed and validated for each antiviral. According to the results of the forced degradation tests, atazanavir and emtricitabine are probably the most unstable in the aquatic environment. Oseltamivir and sofosbuvir begin to lose stability even at slightly elevated temperatures, such as 40 °C. The stability of the tested antivirals depends strongly on the medium’s pH value and the presence of an oxidizing agent. Thus, all six antivirals showed some degree of degradation under the applied alkaline and oxidative conditions, while only emtricitabine, oseltamivir, and ribavirin remained stable under the applied acidic conditions.