Losartan API and Nitrosamines Impurities-Stability Profile Investigation Using HPLC, LC-MS, and In Silico Assessment

Nitrosamines are potent genotoxic impurities with well reported mutagenic and carcinogenic effects. Their presence has been detected in several pharmaceutical products among them losartan, an angiotensin II receptor blocker. Considering the risks already reported for these impurities, the present study aimed to investigate the influence of four common nitrosamines-N-nitrosodimethylamine (NDMA), N-nitrosodiethylamine (NDEA), N-nitrosodiisopropylamine (NDIPA), and N-nitrosodibutylamine (NDBA)-in the stability profile of losartan API. Quantitative assay was conducted through HPLC and LC-MS, with focus on monitoring degradation rate and degradation products under influence of nitrosamines. Predictive data by in silico investigation employing Zeneth Nexus and Spartan were simultaneously studied, considering degradation products, fragmentation pathway and nitrosamines reactivity. The drug residual content showed variability depending on the nitrosamine evaluated and the stressing condition applied. From photolysis, for example the residual content ranged 80%-90%, with a greater decomposition in samples containing nitrosamines. A greater decomposition was also observed in oxidative degradation, with exception for samples containing NDMA. Acid and basic media caused a significant decomposition, with the residual losartan content in a range of 41%-52% and 28%-51%, respectively. From LC-MS analyzes, these impurities were mostly not detected in the degraded samples, suggesting their consumption during the reaction due to their reactivity. A protective effect from nitrosamines can be also reported possibly due to their reactivity against the stressing factor. Seven degradation products were structurally proposed by LC-MS at m/z 449, m/z 447, m/z 366, m/z 338, m/z 274, m/z 391, and m/z 341, some of them predicted computationally by Zeneth.