2,5-bis(Chloromethyl)-4-methoxy-d3-3-methylpyridine is the labeled analogue of 2,5-bis(Chloromethyl)-4-methoxy-3-methylpyridine (C369870), an intermediate in the synthesis of Omeprazole (O635000), which binds covalently to proton pump. It inhibits gastric secretion. Used as an anttiulcerative.