For many years, if a pet ingested rat/mouse poison, the treatment was to induce vomiting, and then follow up with vitamin K. Sometimes activated charcoal or additional treatments were needed. Most cases, if caught early, were not fatal. The active ingredients in most of these rat poisons was a second generation anticoagulant.
In 2008, the Environmental Protection Agency (EPA) passed a law prohibiting the use of long acting anti-coagulants (second generation anticoagulants) in homes. They passed this in effort to reduce secondarily poisoning wildlife. Most manufacturers became compliant with this in the years following, switching to active ingredients such as bromethalin, first generation anticoagulants (such as warfarin), and cholecalciferol (vitamin D3).
d-Con, a major manufacturer of rodenticides, argued with the EPA that bromethalin is a potent neurotoxin, and a ban on second generation anticoagulants would increase the risk of poisoning to children and pets.
As predicted, many companies began using bromethalin as their active ingredient. Bromethalin causes cerebral edema (swelling of the brain), and has no antidote. The treatment is only supportive, often repeated doses of activated charcoal throughout 24 hours, and intensive care hospitalization if swelling develops. The drug remains in the system for a long time, so clinical signs may persist for weeks, and can even become permanent.
In 2014, d-Con announced that they would comply with the EPA mandate by replacing their second generation anticoagulant with a first generation anticoagulant. The benefit to first generation anticoagulants is that there is treatment available if ingestion is caught early and treated immediately. Vitamin K treatment for 3-4 weeks can still be used with this ingredient.
If you must use rat/mouse poisons, please use caution. Put them in areas where your pet and children cannot reach/are not allowed to go. Use traps instead if possible. If you must use rodenticides, look for active ingredients such as diphacinone. Avoid bromethalin at all costs.