Impurity Control
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Impurity Control in Drug Manufacturing

All drugs contain impurities that can arise from the drug substances (Active pharmaceutical ingredients - APIs) or inert materials (excipients). Impurities can also be introduced into the drug product during the formulation processes, packaging, and storage.

Impurities within pharmaceutical products do not offer any therapeutic benefit for a patient and they can be potentially toxic or harmful. Impurities can have many unwanted effects, such as:

  • Decreasing the therapeutic effect
  • Lowering the product shelf-life
  • Inducing toxicity

Impurity control is one of the most important tasks in the manufacturing process and can be controlled by understanding the formation of the impurities. They can also be managed by setting up appropriate controls at places where they either enter or form during the manufacturing process of drug substance and/ or drug product.

Identification, quantification, and control of impurities in APIs and the drug product are critical in drug development as set out in guidance from the FDA. Organic impurities are often free radicals from by-products, intermediates, or degradation products. Inorganic impurities include transition metals, reagents, and ligands.

Electron Paramagnetic Resonance (EPR) spectroscopy is the only technique for the direct and non-invasive detection, identification and quantification of paramagnetic impurities (organic free radicals and transition metals). EPR is able to detect traces of impurities down to parts per billion levels.

EPR spectroscopy detects and identifies traces of transition metals, monitors drug degradation processes that produce and involve free radicals and observes the production of free radicals catalysed by transition metals or other impurities.