Just One Bite EX The Taste Rats and House Mice Just Die For. - The active ingredient is bromethalin, a nerve poison that is extremely toxic to house mice - Norway rats, roof rats and house mice usually consume a lethal dose in a single feeding but it may take two or more days from time of bait consumption for them to die - Due to Stop Feed Action, rats and mice cease feeding after consuming a toxic dose - Effective against anticoagulant resistant rats and mice.