UPDATE: Drug Bust is Deadly Carfentanil Instead of Fentanyl – Scioto Post
The DEA says carfentanil, which is used as a tranquilizing agent for elephants and other large mammals, is 10,000 times more potent than morphine and 100 times stronger than fentanyl. The amount of carfentanil seized in this case could kill between 850,000 to 1.2 million people.
Think of it visually: 3mg of fentanyl (experts say 2mg to 3 mg is the lethal dose) looks like three grains of salt. With carfentanil, it is not even visible. A lethal amount is 2 micrograms to 3 micrograms.