100 milligrams is always fatal, though much smaller doses have killed within 20 minutes. Feeling of suffocation. Face muscles contract and victim looks as if they're grinning. This is followed by very violent and distorting contractions, followed by a period of rest, then an attack of even more violent contractions. Patient is conscious but in agony, unable to speak because of lockjaw.
Pulse is incredibly high.
Death is during a convulsion, from paralysis of respiratory system. Cantharidin Spanish fly. When crushed and rubbed on skin, causes blisters. Taken orally, a small dose results in kidney damage. Larger doses inflame mouth, throat and stomach.