Headspace GC Analysis of Residual Solvents in Pharmaceuticals
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Organic solvents are generally applied during synthesis of drug substances, excipients or during drug product formulation. In the final product, however, they are not desirable due to their toxicity, influence on the quality of crystals of the drug substance and their odor or taste which can be unpleasant for patients. Various manufacturing processes are used to remove the organic solvents in the final product. Nevertheless, some solvents still remain, often in very small quantities, commonly known as residual solvents (RS) .
Residual solvents in pharmaceuticals are defined as volatile organic compounds used in or generated from the manufacture of drug substances, pharmaceutical additives or drug products. They are strictly controlled according to risk classifications from Class 1 to Class 3 based on the risk to human health.
Class 1 includes 5 unacceptable toxicity solvents. They should be avoided unless their use can be strongly justified in a risk-based assessment. Class 2 contains 27 less severe toxicity solvents which should be limited in the final product. And Class 3 classifies less toxic solvents that shall be used whenever practical. Other solvents may be used as well, but only after approval from a regulatory agency. Frequent monitoring for revision of the regulation should be done as other solvents may be added, limits can change due to new safety data announcements, or solvents may shift from one class into another.