Re: What causes death if someone has taken a drug overdose?

By far the commonest cause of death with the two barbiturates mentioned is respiratory depression to the point of respiratory failure which leads to anoxia and cardiac arrest if respiratory (artificial) support is not available. Other less common drugs, such as cyanide, cause disruption of oxygenation at the intracellular level thus causing death much more quickly and regardless of artificial respiration being available.