In 2018, the recall of the drug valsartan due to nitrosodimethylamine (NDMA) impurities sent shockwaves through the pharmaceutical industry. Yet for many observers, the true jolt came in mid-2021 with the recall of Chantix, the widely-used smoking cessation drug. This time, the culprit wasn't NDMA, but nitroso-varenicline—a different nitrosamine drug substance-related impurity (NDSRI) linked to interactions between the manufacturing process and the active pharmaceutical ingredient (API).
The discovery that NDSRIs could emerge in solid drug products from even parts per million levels of nitrite contaminants was surprising, and led to continuing recalls into 2023. The pharmaceutical industry and regulators now confront a daunting reality: NDSRIs potentially taint hundreds, possibly thousands, of medicinal products. And while new regulations have emerged on acceptable intake limits for NDSRIs, challenges persist in updating manufacturing and testing procedures to achieve compliance.
In a conversation with Separation Science, Emiliano De Dominicis, Chemistry Research Director at Mérieux NutriSciences Italy, emphasizes that the battle against nitrosamines is an intensified version of an old struggle. He, alongside colleagues Sergio Fasan and Valentina Abbondandolo, reveals how their firm's broad experience informed their swift action against the NDSRIs threat, turning a potential crisis into an opportunity for industry-wide advancement and education.
Tracing Nitrosamines: A Cross-Industry Tale
Mérieux NutriSciences has been confronting the nitrosamine challenge across various sectors, including tobacco, food, and packaging, for nearly twenty years. De Dominicis distinctly remembers showcasing pioneering work on detecting NDMA in fish and meat with part-per-billion precision at international conferences as early as 2014.
“The pharmaceutical contamination issues that emerged in 2018 involved mostly small nitrosamines, which allowed us to leverage our existing expertise,” he recalls. “However, in the past few years, we've had to evolve our experience to encompass NDSRIs and adapt to changing needs.”
To address this challenge, Mérieux NutriSciences has significantly expanded its resources since 2020. “We’ve dedicated new laboratories specifically for nitrosamines, equipped with advanced analytical equipment, and formed specialized technical teams,” De Dominicis notes. These teams are focused on nitrosamine testing in medicinal products, developing and validating methods, and ensuring the quality control of APIs and finished pharmaceutical products.
Liquid chromatography-tandem mass spectrometry (LC-MS/MS) using a triple quadrupole system has emerged as the team’s preferred technology for nitrosamine testing. This approach covers the vast majority of requests with high sensitivity and multiple reaction monitoring capabilities, aiming for robust methods swiftly transferable between low- and high-resolution instruments.
De Dominicis also underscores the need for straightforward sample preparation, especially when dealing with complex matrices. Prior experience in handling nitrite-rich products such as tobacco has provided valuable skills in developing purification and concentration strategies that minimize the chance of generating nitrosamine artifacts.
Advanced Approaches to NDSRIs Identification
Identifying nitrosamine drug substance-related impurities (NDSRIs) in pharmaceuticals presents a complex challenge. A wide array of drug compounds are theoretically susceptible to forming NDSRIs, yet their actual development is not straightforward. The formation of many potential NDSRIs is often chemically unfeasible due to factors such as steric hindrance or extended resonance. Adding to the complexity, some NDSRIs only become apparent under specific, biologically relevant conditions.
A key instrument in Mérieux NutriSciences' toolkit is the Nitrosation Assay Procedure (NAP) test. One of the possible applications of this test is designed to simulate in vivo conditions, such as in the stomach, where nitrosamines may form by breaking down excess nitrites in an acidic environment. Originally stemming from 1978 World Health Organization directives, the NAP test has gained prominence recently, driven by technological advances in analytical methods.
The firm employs several NAP protocols, including the WHO-referenced test and internal procedures for intense nitrosation reactions. These tests are versatile, extending to the synthesis of technical standards in cases where reference compounds are unavailable, and using high-resolution mass spectrometry for preliminary screenings.
“Clients often seek our advice, not just for clarification on new regulations, but also to discuss and brainstorm the long-term trajectory of these guidelines,” explains De Dominicis. “It's vital to not just comply with current standards but—more importantly—to strategically prepare for future developments. Anticipating these changes is key to our approach.”
Achieving required sensitivity in NDSRI testing often takes sub-part-per-billion detection of impurity levels. Mérieux NutriSciences has honed its approach to these tasks through advanced chromatography. These techniques are essential in distinguishing slight structural variations between nitroso-APIs and APIs.
“While mass spectrometry is key for selectivity, sensitivity, and specificity, it sometimes falls short,” De Domincis explains. “Techniques including enantioselective chromatography and ion mobility are crucial in reaching difficult targets and ensuring reliable results for our customers.”
Opening Pandora’s Box
Reflecting on the industry's response to the potential risk of nitrosamine impurities in APIs, De Dominicis offers a compelling perspective. “While estimates vary, we understand that at least 20–22% of APIs or molecules are related to secondary amines as precursors. This necessitates considering both the impurities and the additional products that can be derived,” he explains. He acknowledges the immense scope of this issue, describing the challenge as a 'Pandora’s box' that defies simple quantification.
“It's clear this issue is substantial," observes De Dominicis. “Pharmaceutical companies are now well-equipped to assess, evaluate, and manage these risks. They are prepared to implement corrective actions, conduct thorough root cause analyses, and adapt formulations as necessary. This topic is poised to remain relevant and critical for many years to come.”
This article is featured in our May 2024 publication, Pharmaceutical Purity and Precision. Find out what’s happening in the world of pharmaceutical impurity analysis and learn about the latest topics and techniques.
