Carfentanil is an extremely potent derivative of fentanyl, it is 10,000 times the potency of morphine, 4,000 times that of heroin and 100 times that of fentanyl. The lethal dose of fentanyl in humans is two milligrams, equal to a few grains of salt, as such it only takes an extremely tiny amount of pure carfentanil to kill, even getting the powder on skin is enough to cause a fatal overdose. It is the most potent opioid commercially produced, its primary use is in tranquilizing large animals like elephants and rhinoceroses and can only legally be obtained by veterinarians. Illicit use of carfentanil is on the rise world wide, it is usually cut with heroin in order to allow long time users with a tolerance to get a better high, however most people using it are not aware of just how potent and toxic it is in pure form. Plus it is so potent that measuring dosages is difficult.