STABILITY-INDICATING PROTON NUCLEAR-MAGNETIC-RESONANCE SPECTROSCOPIC ASSAY-METHOD FOR FUROSEMIDE IN TABLETS AND INJECTIONS

A simple, specific, and accurate proton nuclear magnetic resonance (H- 1-NMR) spectroscopic method has been developed for the identification and assay of furosemide and its degradation product, 4-chloro-5-sulfam oylanthranilic acid (CSA), in tablets and injections. Dissolution of t he sample in D2O-NaOD resulted in a solution yielding the required sep aration among the resonance signals of furosemide, CSA, and tert-butyl alcohol, the internal standard. The mean +/- SD recovery values of fu rosemide and CSA from 10 synthetic formulations were 99.6 +/- 0.8 and 98.9 +/- 1.7%, respectively. Commercial tablets (6 lots) and injection s (5 lots) of furosemide were assayed by the proposed method and found to contain 53.1-99.8% furosemide and 0.3-45.2% CSA.