Impurity Profiling and Structural Elucidation of Unknown Degradation Products in Efavirenz Using Integrated HPLC, LC-MS, and NMR Techniques

A comprehensive impurity profiling study was conducted on Efavirenz, an essential antiretroviral drug, using an integrated analytical approach involving HPLC, LC-MS, HRMS, and NMR spectroscopy. A stability-indicating HPLC method was developed and validated as per ICH guidelines, demonstrating excellent linearity (R² = 0.9998), precision (RSD < 2%), accuracy (98–102%), and robustness. Forced degradation studies under acidic, alkaline, oxidative, thermal, and photolytic conditions revealed significant degradation, with alkaline stress being the most severe (33.81% degradation). Nine major degradation products were isolated and characterized using LC-MS and NMR. Structural elucidation confirmed the formation of novel impurities, including cyclized and hydroxylated derivatives. The study provides valuable insights into the degradation pathways of Efavirenz and supports regulatory compliance and quality assurance in pharmaceutical manufacturing.