The fastest acting rat poison is the Fastrac Blox rat poison.
The Fastrac Blox kills rats and mice within 2 days by causing internal bleeding in the rats or mice.
There's no mouse or rat poison that actually kills rats or mice instantly as all rat poison and mouse poison kills mice and rats slowly overtime.
Killing rats and mice instantly requires the use of rat traps and mice traps.
The mouse and rat poison will not kill rats or mice instantly but instead the mouse poison and rat poison takes time and kills the rats and mice slowly.
The rat and mouse poison causes internal bleeding and prevents the mice or rats blood from clotting so that they die of internal bleeding.
So you might see the same rat or mice out for a few days before they actually die.
The best way to kill a rat or mice is to kill it instantly using rat traps or mice traps.