Fentanyl is used in the care of cancer patients as they approach the end of their lives. It is also used to treat pain after serious surgical operations. Since it affects the central nervous system, fentanyl is also used as an anesthetic before an operation. It puts patients into a deep sleep-like state, in which they relax and feel no pain. The dose of the drug depends on the severity and the duration of the operation. Fentanyl is 50 times stronger than heroin, another common illicit opiate drug. Fentanyl is a painkiller 70 times stronger than morphine. Its euphoria-producing effects have made it a common illicit drug. But 2 mg is enough to kill you. Why is the drug sold anyhow on US streets ?