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Base mediated hydrolysis of Irbesartan resulted in formation of three degradants.Structures of all the three degradants were established by extensive analysis of HRMS and 1D and 2D NMR spectra.Two of the three isolated degradants were found to be new.The structure of DP-3 was found to be different compared to that of earlier proposed one with same molecular weight.To assess the stability of Irbesartan under stress conditions, and identify the degradation products, it was subjected to hydrolytic and oxidative stress, according to ICH guideline Q1A (R2). The drug showed degradation only in basic conditions, while it was stable to other stress conditions. Three degradation products were formed, which were separated on a C-8 column employing prep HPLC using gradient elution. The structures were established by extensive 1D and 2D NMR spectroscopic studies and mass spectra. The products were identified as (2′-(2H-tetrazol-5-yl)-[1,1′-biphenyl]-4-yl)methanamine (DP-1), N-((2′-(2H-tetrazol-5-yl)-[1,1′-biphenyl]-4-yl)methyl)pentanamide (DP-2) and N-((2′-(2H-tetrazol-5-yl)-[1,1′-biphenyl]-4-yl)methyl)-1-pentanamidocyclopentane-1-carboxamide (DP-3). One of the three, DP-1, was reported earlier. However, its structure has not been elucidated by NMR. The other two degradants are novel and are being reported here for the first time.