Multiple-dose, or chronic, rodenticides are mostly anticoagulants with a cumulative toxic effect. Death occurs about 4 or 5 days after the rodent first eats the bait. These do not produce bait-shyness and are among the safest rodenticides. Because they act slowly, anticoagulant baits may serve as their own prebait. Anticoagulants kill by inhibiting the clotting ability of the blood, so the animal dies of internal bleeding.
Mice are generally less susceptible to anticoagulant baits than are rats.
Many different types and preparations of rodenticides are effective. Your specific situation dictates which one is best to use. Rats and mice have poor eyesight and are essentially colorblind. Therefore, poison baits can be dyed for safety. Poison grains and pellets which have been dyed a bright color can easily be avoided by humans.