An anaesthesist friend of mine once told me that there are two kinds of muscles - the ones you can actively control (such as muscles in arms and legs and also the muscles for breathing) and those you cannot, such as your heart and intestine-muscles (around the gut etc.). The latter has a different kind of receptors and isn’t affected by the stuff that they use in hospitals to put you down, but since the breathing is stopped, you’ll always be intubated.

I guess this poison is of the same kind but I don’t know the technicalities…