"If it is not pure drugs that kill, but impure drugs and the mixture of drugs, then the myth of the heroin overdose can be dangerous. If users had a guaranteed pure supply of heroin which they relied on, there would be little more likelihood of toxic doses than occur with narcotics administered in a hospital.
"But when people take whatever they can off the street, they have no way of knowing how the drug is adulterated. And when they decide to augment heroin's effects, possibly because they do not want to take too much heroin, they may place themselves in the greatest danger."
Peele, Stanton, MD, (1998), The persistent, dangerous myth of heroin overdose. Last accessed August 31, 2021.