Opioid

Opioids are substances that act on opioid receptors to produce morphine-like effects. Opioids include opiates, an older term that refers to such drugs derived from opium, including morphine itself. Other opioids are semi-synthetic and synthetic drugs such as hydrocodone, oxycodone and fentanyl; antagonist drugs such as naloxone and endogenous peptides such as the endorphins. Opioid drugs are predominantly central nervous system agents, most often used medically to relieve pain. The terms opiate and narcotic are sometimes encountered as synonyms for opioid. Opiate is properly limited to the natural alkaloids found in the resin of the Papaver somniferum (opium poppy) although some authorities include semi-synthetic derivatives.Narcotic, derived from numbness or sleep, is now a legal term that refers to cocaine and opioids, and their source materials; it is also loosely applied to any illegal or controlled psychoactive drug. The term has pejorative connotations and its use is generally discouraged.