Introduction

The detection of N-Nitrosamines in AT1 receptor antagonists like Valsartan in late 2018 has sparked significant attention and discussions in pharmaceutical research and regulatory circles. This is due to their potential mutagenic effects as DNA alkylating agents. Other drugs, including propranolol, varenicline, and ranitidine, have also undergone recalls or suspensions due to nitrosamine-related concerns.¹

Nitrosamines can be generated when a nitrosatable amine group combines with nitrosating agents, often sourced from inorganic nitrite, under specific conditions that promote their formation.²

Background The 2018 global recall of valsartan due to NDMA contamination raised significant concerns within the pharmaceutical industry and among regulatory authorities. Subsequent recalls of other tetrazole containing ARBs, such as losartan and irbesartan, contaminated with elevated levels of nitrosamines followed suit. Effectively addressing the potential risk of nitrosamine contamination in pharmaceuticals necessitates substantial knowledge and resources to gather the required information for risk assessment.²

This includes access to a reliable laboratory facility, reference materials, highly specific and sensitive instrumentation capable of detecting trace levels of contamination, proficient data management, and, notably, time – a limited resource. Consequently, supporting tools, such as shared databases containing information on drugs and excipients, screening models for assessing nitrosamine formation potential, and in silico models aiding in toxicity estimation, have proven to be valuable in addressing and mitigating the risks associated with nitrosamine contamination in pharmaceuticals.¹

Identification Methods High-Performance Liquid Chromatography (HPLC) combined with spectrophotometric detection is a widely utilized laboratory method for impurity analysis and is typically recommended for routine quality control procedures. Gas Chromatography (GC) is a potent technique for both qualifying and quantifying volatile and semi- volatile impurities in pharmaceuticals, including residual solvents outlined in pharmacopoeia monographs. Nitrosamines, varying in polarities, can be effectively separated using stationary phases with moderate to high polarity.

In addition to chromatographic analysis, certain sensors are employed for the determination of nitrosamines. For instance, cucurbit [n]uril (CB [n]) and its derivatives have been utilized for the detection and quantification of nitrosamines associated with cancer.³

Scientific Reasoning and Experiments:

Animal studies have demonstrated a discernible dose- response correlation between exposure to NDMA (N nitrosodimethylamine) and the development of tumors in the liver, lung, and kidneys in certain species. The prevalence of liver tumors is notably higher, aligning with NDMA's mechanism of action, although mice seem to exhibit increased susceptibility to lung tumors. This variation in tumor incidence among species is attributed to differences in the CYP2E1 enzyme, which is species-specific. These findings are in line with assessments by the International Agency for Research on Cancer (IARC) in 1978 and the National Toxicology Program (NTP) in 2016⁴

The existence of nitrosamines, including NDMA (N nitrosodimethylamine), in foods and beverages has been recognized for many years, constituting a substantial pathway for human exposure to these compounds. NDMA can be generated in foods during processing, preservation, and/or preparation from precursor substances like nitrites and amines, which are naturally present in or intentionally added to certain food items. This information is in accordance with the findings of the World Health Organization (WHO) in 2008. Foods that are commonly preserved with nitrites, such as meats and cheeses, are particularly prone to containing NDMA. As mentioned earlier, for NDMA (N nitrosodimethylamine) to present a cancer risk, it needs to undergo metabolism into a reactive intermediate called the methyldiazonium ion, a process facilitated by the CYP2E1 enzyme. In humans, CYP2E1 is predominantly, if not exclusively, located in the liver. Consequently, the most biologically plausible cancer that could theoretically be linked to NDMA exposure is liver cancer.⁵

Conclusion:

Examining a process to identify potential nitrosamine formation or introduction is a complex task. A thorough analysis, including all possible sources of nitrosamines and their precursors, even those less evident, lays the groundwork for a comprehensive assessment of nitrosamine risk.⁴