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August 14, 2024
Ascorbic acid, and other nitrite scavengers, have been shown to act as functional excipients in drug products that can reduce nitrosamine formation by blocking nitrosation reactions.
Mitigating nitrosamine risks: the role of ascorbic acid in drug safety.
Nitrosamines are abundant carcinogens found in a number of sources, including processed food and tobacco smoke. They have been studied for decades, with their first link to cancer being described back in the 1950s.2 But concerns about nitrosamines in the pharmaceutical industry only really came to the fore in 2018, when they were found in some common drugs, including ranitidine, nizatidine and metformin, resulting in a number of recalls.1 Since then, regulatory bodies – including the U.S. Food & Drug Administration (FDA) – have increased scrutiny of nitrosamines, requiring companies to evaluate, measure and mitigate them in their products. While the acceptable intake limits will no doubt change as the evidence for the safety and carcinogenicity of nitrosamines evolves, the need for a solution to control their presence will stay. During her presentation – ‘Ascorbic acid – A safe and effective excipient for nitrosamine mitigation in drug products’ – Dr. Bayne outlined the use of nitrite scavengers – such as the vitamins ascorbic acid and alpha-tocopherol - as functional excipients in drug formulations. But what are they, and how can they help? This article provides key insights from her talk.
Nitrosamines are formed by a chemical reaction between a nitrosating agent and a secondary or tertiary amine. The conditions for nitrosamine formation can be present at every stage of drug production, making it particularly challenging to control. The risk can be impacted by variables including the active pharmaceutical ingredient (API) chemical structure, formulation excipients, solvents, water, manufacturing process, and even packaging and storage decisions. There are many strategies that can be put in place to deal with the formation of nitrosamines, including strong qualification programs for new ingredients and ensuring the levels of nitrosating agents are kept low in formulations. One solution that has the potential to be helpful is the use of nitrite scavengers to reduce or stop nitrosamines from being formed.
Nitrites are often present as impurities in drug products and can be converted into nitrosating agents like nitrous acid. Nitrite scavenging is therefore an effective way to inhibit the formation of nitrosamines. Nitrite scavengers work by quenching reactive nitrites and ultimately block the nitrosation reaction. There are many known nitrite scavengers, but not all are suitable for use in drug products. Only a few are listed on the FDA’s inactive ingredient database (IID)3, but even these have variable properties relating to their activity, the environment in which they can work, and their interactions with external compounds. So far, ascorbic acid and alpha-tocopherol have shown consistently good results, and both have been mentioned by the FDA as strategies worth exploring for nitrosamine mitigation.4,5,6
Multiple studies have demonstrated that ascorbic acid and alpha-tocopherol are safe and effective nitrite scavengers; recent discussions also indicate that these scavengers may not modify drug absorption.5,7,8,9 Internal research at dsm-firmenich, outlined in the presentation, includes further studies on the efficacy of ascorbic acid in reducing nitrosamine formation. Firstly, we looked at the ability of ascorbic acid to decrease the amount of nitrite in a placebo tablet. We saw that it was able to reduce nitrite levels when used in a tablet produced by either direct compression or wet-granulation, with its effects increasing with higher concentrations – up to one percent. Next, we investigated ascorbic acid in a standard tablet formulation with a model API. We subjected a control and a formulation containing one percent ascorbic acid to two weeks of stress testing at high temperature and humidity and compared nitrosamine content after this time. The presence of ascorbic acid significantly reduced nitrosamine levels in the tablet. This effect was also repeated in two other drug models with different formulations and characteristics.
Using low levels of nitrite scavengers – even below one percent – in combination with low nitrite level APIs and excipients has been shown to significantly minimize nitrosamines. However, ascorbic acid is commercially available in a range of purities and grades, so it is important to evaluate how this will impact its efficacy when developing a formulation. In general, the smaller particle size of ultra-fine powders ensures the closest contact between the nitrite scavenger and nitrite source, leading to higher efficiency. It is also important to consider the manufacturing route, as wet-granulation poses a higher risk of nitrosamine formation compared to direct compression. Vitamin purity itself is also a major consideration during drug development, as it ultimately impacts the quality of the final formulation. As a purpose-driven innovation partner in the pharmaceutical industry, dsm-firmenich can provide not only the high-quality products, but also the technical guidance to successfully use nitrite scavengers within drug products, whether reformulating existing medicines or developing new pharmaceuticals.
Click the button below to watch Dr. Bayne’s full presentation, and study the evidence in more detail.
1. Li K, Ricker K, Ponting DJ, Tsai FC et al. Estimated cancer risks associated with nitrosamine contamination in commonly used medications. Int. J. Environ. Res. Public Health. 2021; 18(18):9465. doi: 10.3390/ijerph18189465
2. Magee PN., Barnes JM. The production of malignant primary hepatic tumours in the rat by feeding dimethylnitrosamine. Br. J. Cancer. 1956; 10:114–122. doi: 10.1038/bjc.1956.15
3. Food and Drug Administration. Inactive Ingredients Database. https://www.accessdata.fda.gov/scripts/cder/iig/index.cfm (accessed 12 August 2024)
4. Bayne AV, Misic Z, Stemmler RT et al. N-nitrosamine mitigation with nitrite scavengers in oral pharmaceutical drug products. J Pharm Sci. 2023; 112(7):1794-1800. doi: 10.1016/j.xphs.2023.03.022
5. Homšak M, Trampuž M, Naveršnik K et al. Assessment of a diverse array of nitrite scavengers in solution and solid state: A study of inhibitory effect on the formation of alkyl-aryl and dialkyl N-nitrosamine derivatives. Processes. 2022; 10(11):2428. doi: 10.3390/pr10112428
6. Food and Drug Administration. Updates on possible mitigation strategies to reduce the risk of nitrosamine drug substance-related impurities in drug products. 2021. https://www.fda.gov/drugs/drug-safety-and-availability/updates-possible-mitigation-strategies-reduce-risk-nitrosamine-drug-substance-related-impurities (accessed 12 August 2024)
7. Shakleya D et al. Communication at the FDA and CRCG hosted public workshop on 'Mitigation strategies for nitrosamine drug substance related impurities: quality and bioequivalence considerations for generic products'. Universities at Shady Grove, Rockville, Maryland, USA and on-line. 15 June 2023
8. Bode C. Communication at the FDA and CRCG hosted public workshop on 'Mitigation strategies for nitrosamine drug substance related impurities: quality and bioequivalence considerations for generic products'. Universities at Shady Grove, Rockville, Maryland, USA and on-line. 15 June 2023
9. Wang X et al. Communication at the 14th Annual APS PharmSci International Conference. Reading, UK. 5-7 September 2023
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