The most effective rat poisons are those that use bromethalin, zinc phosphides or vitamin D derivatives as active ingredients. These types of poisons kill rats quickly, and they are effective against increasingly common anticoagulant-resistant rats.
Zinc phosphides work by releasing a toxic gas after coming into contact with a rat's stomach acid. Zinc phosphides kill most rats after a single feeding and typically kill rats within one day.
Bromethalin is a neurotoxin that kills a rat by flooding its brain with toxic chemicals. Bromethalin works extremely quickly, killing the rat in as little as a few hours. While still dangerous, bromethalin is also much less toxic to children and pets than other rat poisons.
Vitamin D derivatives work by flooding the rat's body with overdoses of vitamin D. While slower than bromethalin, vitamin D derivatives work more quickly than zinc phosphides.
Some of the most common rat poisons on the market are anticoagulants, such as warfarin, fumarin and brodifacoum. All of these substances work by inhibiting a rat's ability to form blood clots. After eating the poison, the rat can no longer form clots, and it eventually hemorrhages internally and dies. Despite their popularity, anticoagulants are poor choices for poisoning rats. These poisons take days to kill rats, are highly toxic to children and pets, and many rat colonies are now resistant or immune to their effects.