Poisons (drugs) did not magically change their chemical structure and start causing death by cardiac arrest. Any poisoning drug OD is a respiratory emergency. Our diaphragm still controls our breathing, adult needs 1.5 liters of air every 5 seconds. Naloxone is second line defense because it does not always work and every second you withhold the air from any respiratory patient every cell, tissue and organ is dying lack of oxygen, especially the brain. Note massive doses Naloxone used, and continuous respiratory assist. Rescue breathing lay responder same.