Nitrosamines are classified by the ICH M7(R1) Guideline as Class 1 impurities, “known mutagenic carcinogens,” based on both rodent carcinogenicity and mutagenicity data. They are categorized by the International Agency for Cancer Research (IARC) as 2A – Probable Carcinogens based on data on a number of species studied. More other impurities including like N-nitrosodiethylamine (NDEA), N-nitrosoethylisopropylamine (NIEPA), N-nitrosodiisopropylamine (NDIPA), N-nitrosodibutylamine (NDBA), and N-nitrosomethyl-4-amino-butyric acid (NMBA) are also classified as potential nitrosamine impurities. In February 2021, the FDA has issued a guidance “Control of Nitrosamine Impurities in Human Drugs, Guidance for Industry”. This document provides guidance on steps to detect and prevent unacceptable levels of nitrosamine impurities in pharmaceutical products.