Most of the time, poison is used to kill people. However, there is actual poison used in history that allowed people to have control over others. This is not even science fiction, it is science reality. The reason we do not discuss it much is that poison is often used to kill rather than control.
Some poison can give people visions or hallucinations while others can force them to have a sleepwalking condition where they blackout and do stuff they assumed was only a dream. This was most famously used in the mythological story of Hercules where he was poisoned and killed his wife and children in a sort of rage fit. You could possibly give this same type of stuff to several people and that could cause a real zombie apocalypse of sorts.