Oxidation of betrixaban to yield N-nitrosodimethylamine by water disinfectants

Degradation of betrixaban, an oral anticoagulant recently approved by the U.S. Food and Drug Administration (FDA), and its N-nitrosodimethylamine (NDMA) formation potential were studied mechanistically in the presence of monochloramine (NH₂Cl), free chlorine, and ozone. Upon monochloramination, the formation of NDMA exceeded 1% at basic pH and was significant at circumneutral pH as well. The kinetic studies revealed that the reaction between betrixaban and monochloramine followed pseudo-first-order reaction kinetics. Increasing monochloramine concentration, its reaction time, and pH all significantly enhanced the NDMA formation yield, which also increased three-fold in the presence of bromide during monochloraminantion. The presence of nitrite inhibited the formation of NDMA under the same conditions. This study revealed a new potent and significant precursor of NDMA, indicating that monochloramination of waters containing betrixaban can lead to the formation of NDMA and other disinfection by-products such as dichloroacetonitrile (DCAN) and dimethylformamide (DMF). Moreover, chlorination of betrixaban by hypochlorite also yielded NDMA, albeit at two orders of magnitude lower yield than chloramination, while no NDMA formation was observed from ozonation of betrixaban.