Degradation study of irbesartan: Isolation and structural elucidation of novel degradants.

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.