Carfentanil is the most potent opioid drug available. It can cause extreme drowsiness or altered sensorium, cold, clammy skin, disorientation, blue hands and feet due to decreased oxygen, depressed breathing, sedation, and pinpoint pupils. The only hope of saving the patient is to administer one dose of naloxone before the arrival of the emergency personnel to slow down the process. The street name grey death suggests that the body turns grey or blue due to the decreased oxygen-carrying capacity by the body. Historically it has caused the death of countless people in the Moscow theatre incident (800 hostages) where it was used in an aerosol as a weapon of mass destruction, and the patients could not be revived in time. About 650 people were hospitalized. Every year many people in the United States due to heroin laced with carfentanil.