An opioid antagonist medication approved by the FDA to reverse an opioid overdose. A commonly used trade name is Narcan. It displaces opioid drugs (such as morphine or heroin) from their receptor and prevents further opioid receptor activation. It is used by first-responders and emergency departments, as well as prescribed to patients who use illicit opioids or to patients who are prescribed opioids and are at higher risk of overdose. It is also included in several forms of buprenorphine such as Suboxone; when taken properly, the naloxone in Suboxone is inert and is included simply as a diversion deterrent.