A cat that eats cockroach medicine may have an attack in about 2 to 4 hours, but if the cat eats less, it may not have an attack. It depends on how much cockroach medicine the cat has eaten and whether the poison is strong or not. . After cats eat cockroach poison, they may develop poisoning symptoms such as vomiting, diarrhea, foaming at the mouth, convulsions, and mental disorders. Once found, they need to be sent to a pet hospital for treatment in time to avoid life-threatening consequences.