Pancuronium bromide
Pancuronium bromide paralyzes the breathing muscles along with all of the other muscles.  This means that pancuronium bromide will stop a person from breathing.  In hospitals, a person who is given pancuronium bromide is then   a tube is put down their throat to pump oxygen into their lungs.  This gives the body the oxygen it needs until the medication wears off, the breathing muscles can work again, and they can breathe in oxygen on their own.