Fentanyl

Definition of fentanyl citrate
National Cancer Institute

fentanyl citrate

(FEN-tuh-nil SIH-trayt)
A drug used to treat severe cancer pain that occurs even though the patient is already taking opioids. It is also used during anesthesia for surgery. Fentanyl citrate binds to opioid receptors in the central nervous system. It is a type of analgesic agent and a type of opioid.

Source: NCI Dictionary of Cancer Terms