Ensuring the safety, efficacy, and quality of pharmaceutical products requires a thorough understanding of the impurities that may be present throughout the development and manufacturing process. These impurities, even at trace levels, can compromise therapeutic performance or pose risks to patients, making their detection and control a critical aspect of drug development. Impurity profiling integrates advanced analytical techniques with regulatory frameworks to detect, identify, and quantify these substances, supporting the production of compliant and high-quality medicines.
Understanding Pharmaceutical Impurities: Classification and Sources
The US Food and Drug Administration (FDA) defines impurities in drug substances and drug products as any component of the drug that is not the active pharmaceutical ingredient (API) or an excipient. These substances can originate from various stages of the manufacturing process, including synthesis, formulation, storage, and degradation, and can be classified as:
- Organic impurities: arising from starting materials, by-products, intermediates, degradation products, and reagents.
- Inorganic impurities: metallic or non-metallic elements, often originating from raw materials, catalysts, manufacturing equipment, or the environment.
- Residual solvents: volatile organic compounds used or produced during the manufacturing of drug substances or excipients.
- Extractables and leachables: compounds that migrate from packaging, container-closure systems, or medical devices into the drug product, either under aggressive laboratory conditions (extractables) or during normal storage and use (leachables).
Understanding what are the sources of impurity in pharmaceuticals allows for proactive control strategies. For example, nitrosamine impurities, detected in several widely used drugs, have led to global recalls and stricter regulatory oversight, highlighting the need for early detection and preventive measures.
Analytical Techniques for Drug Impurity Profiling
The analysis of drug impurities requires both qualitative and quantitative analysis of drugs to identify the type of impurity and measure its concentration, respectively. Techniques employed for impurity profiling must provide high sensitivity, specificity, and reproducibility.
Among the most widely used approaches are:
- Ultra high-performance liquid chromatography (HPLC): the gold standard for impurity analysis, capable of separating trace impurities.
- Gas chromatography (GC): ideal for volatile organic impurities, such as residual solvents.
- Mass spectrometry (MS): often coupled with separation techniques, such as chromatography (LC-MS), provides molecular weight information and structural details of unknown impurities, often coupled with chromatography (LC-MS) used for identification and quantitation.
- Spectroscopic techniques: often coupled with chromatographic methods for comprehensive profiling, offer detailed structural information. Nuclear magnetic resonance (NMR) and Fourier transform infrared spectroscopy (FTIR) are the most used.
- Inductively Coupled Plasma Mass Spectrometry (ICP-MS): a highly sensitive technique for detecting and quantifying elemental impurities in drug products.
Advanced laboratories integrate these techniques into validated workflows that address tests for impurities in drugs by combining high-throughput screening with confirmatory analysis. The use of orthogonal methods also ensures the detection of impurities that may otherwise remain undetected.
Regulatory Standards and Impurity Limits: ICH and FDA Guidelines
Compliance with global standards is essential to guarantee product safety and avoid regulatory setbacks. The International Council for Harmonisation (ICH) Guidelines, particularly Q3A (for drug substances) and Q3B (for drug products), set thresholds for reporting, identification, and qualification of impurities. These thresholds are based on factors such as the maximum daily dose and the potential toxicity of the impurity.
The FDA inspection framework emphasizes strict adherence to current Good Manufacturing Practices (GMP), requiring comprehensive documentation of impurity testing, validated analytical methods (including HPLC impurity analysis), and thorough batch records. Additionally, Annex 4 of the WHO Good Practices for Pharmaceutical Quality Control Laboratories provides critical guidance to ensure data integrity, reliability, and consistent quality in impurity profiling.
In response to safety concerns raised by a critical analysis of drug product recalls due to nitrosamine impurities, regulatory agencies have issued targeted guidance that enforces lower detection limits, mandatory risk assessments, and detailed mitigation plans. These requirements highlight the importance of sensitive analytical technologies and robust impurity control strategies to effectively detect and manage hazardous impurities.
Case Studies and Best Practices in Impurity Detection and Qualification
Real-world examples highlight the crucial role of advanced impurity profiling in ensuring drug quality and patient safety. A detailed study using bidimensional LC-UHPLC-MS/MS enabled sensitive quantitative analysis of drugs by accurately quantifying genotoxic N-nitrosamine impurities in rifampicin, notably 1-methyl-4-nitrosopiperazine (MNP), formed during synthesis and degradation processes. This work validated a reliable analytical approach to control nitrosamine levels within regulatory limits and minimize recall risks.
Similarly, impurities affecting paracetamol influence its crystallization behavior and final product quality. Specific impurities alter polymorphic forms and particle properties, impacting drug performance and processability. This underscores the need for stringent impurity analysis not only for chemical safety but also for their physical effects on crystallization, ensuring consistent efficacy.
These cases demonstrate the integration of sensitive HPLC impurity analysis, rigorous risk assessments, and regulatory-aligned strategies to manage impurities in drugs effectively.
Best practices in impurity in pharmaceutical analysis involve:
- Implementing risk-based assessments to prioritize critical impurities
- Using validated analytical methods with high sensitivity
- Incorporating stability studies to monitor degradation products over time
- Aligning impurity qualification strategies with both ICH and FDA requirements
These practices not only address the qualification of drug impurity but also enhance overall quality assurance throughout pharmaceutical development. Advanced analytical capabilities for impurity profiling are now a regulatory requirement and a competitive advantage. Laboratories equipped with chromatography, spectroscopy, and modeling technologies provide precise data to enable early risk mitigation by detecting trace contaminants and implementing swift corrective actions to meet international standards.
Partnering with an expert provider in the identification and determination of impurities, including qualitative and quantitative analysis with regulatory-compliant method validation, optimizes development timelines and reduces the risk of product recalls.
For pharmaceutical, biopharmaceutical, and chemical manufacturers seeking to strengthen their impurity control strategy, advanced services from AMSbiopharma offer tailored solutions to ensure product safety and regulatory compliance.
Contact us now to safeguard your development program with cutting-edge expertise!
References
European Medicines Agency. ICH Q3A (R2) Impurities in new drug substances – Scientific guideline [Internet]. Amsterdam: EMA; [updated 2023; cited 2025 Jul 20]. Available from: https://www.ema.europa.eu/en/ich-q3a-r2-impurities-new-drug-substances-scientific-guideline
European Medicines Agency. ICH Q3B (R2) Impurities in new drug products – Scientific guideline [Internet]. Amsterdam: EMA; [updated 2023; cited 2025 Jul 21]. Available from: https://www.ema.europa.eu/en/ich-q3b-r2-impurities-new-drug-products-scientific-guideline
Liu KT, Chen CH. Determination of Impurities in Pharmaceuticals: Why and How? [Internet]. Quality Management and Quality Control – New Trends and Developments. IntechOpen; 2019. Available from [cited 2025 Jul 20]: http://dx.doi.org/10.5772/intechopen.83849
Kumari M, Tripathy DB, Gupta A. Analytical methods and their significance in pharmaceutical process impurities: A review. Macromol Symp. 2024;413(1). doi: 10.1002/masy.202300026
World Health Organization. Annex 4: Good practices for pharmaceutical quality control laboratories [Internet]. Geneva: WHO; 2020 [cited 2025 Jul 20]. Available from: https://cdn.who.int/media/docs/default-source/medicines/norms-and-standards/guidelines/quality-control/trs1052_annex4.pdf?sfvrsn=d3dfc0cc_4&download=true
de Souza GFP, Araujo Vieira Matos MF, de Castro Aglio T, Salles AG Jr, Rath S. A comprehensive LC-UHPLC-MS/MS method for the monitoring of N-nitrosamines in lipophilic drugs: A case study with rifampicin. J Pharm Biomed Anal. 2023 Nov 30;236:115685. doi: 10.1016/j.jpba.2023.115685
Urwin SJ, Yerdelen S, Houson I, ter Horst JH. Impact of impurities on crystallization and product quality: A case study with paracetamol. Crystals. 2021;11(11):1344. doi: 10.3390/cryst11111344