A Nutshell on Characterized and Reported Related Substances in Active Pharmaceutical Ingredients and Dosage Forms

Abstract

The impurity profiling plays a pivotal role in ensuring the presence of impurities in drug substances and drug products, even in trace amounts, can significantly compromise their safety and efficacy. This article underscores the critical importance of impurity evaluation through a systematic approach encompassing classification, isolation, and structural characterization. A comprehensive literature survey has been conducted, covering 378 pharmaceutical products—including both active pharmaceutical ingredients (APIs) and finished formulations—across diverse therapeutic categories. The article summarizes data on related substances or metabolites, types of impurities, analytical techniques employed, and characterization outcomes in a tabulated format. The characterization details include chromatograms, spectra, fragmentation pathways, metabolic and degradation pathways, plausible mechanisms of impurity formation, and spectral data of APIs and pharmaceutical products. The findings aim to guide researchers and regulatory professionals in developing robust impurity profiling strategies that align with global standards and promote patient safety. 

Cite this article as: PKC, Tabassum S. A nutshell on characterized and reported related substances in active pharmaceutical ingredients and dosage forms. Trends in Pharmacy . 2026, 3, 0015, doi: 10.5152/ TIP.2026.25022.