Acetaminophen: First used clinically in the U.S. in 1950, acetaminophen was launched in the commercial market under the brand name Tylenol in 1955. It is widely used to relieve pain and reduce fever because it is not habit-forming and has few side effects. Acetaminophen is available over the counter, and by prescription at stronger doses and when combined with opioids.

Acute pain: Pain that is directly related to an injury and typically lasts less than six months. It often responds to treatment with analgesic medications and treatment of the precipitating cause.

Agonists: Drugs that activate specific receptors in the brain. For example, full agonist opioids activate opioid receptors in the brain, reducing pain and producing feelings of euphoria.

Analgesics: Opioid and nonopioid medications that are intended to relieve pain. 

Antagonists: Drugs that block the effects of agonists by attaching to receptors without activating them. Naloxone is an opioid antagonist that saves lives by reversing the effects of opioid overdoses.  

Buprenorphine: Approved by the Food and Drug Administration for opioid addiction treatment in 2002, buprenorphine is an opioid partial agonist that suppresses symptoms of withdrawal. It produces relatively mild opioid effects that level out at moderate doses, even if more buprenorphine is taken. Unlike methadone, which must be dispensed in a medical clinic, buprenorphine treatment may occur in settings including offices, hospitals and correctional facilities by specially licensed providers.

Carfentanil: A synthetic opioid not approved for human use in any capacity. Carfentanil is 100 times more powerful than fentanyl, from which it is derived, and can be lethal even in very small doses. It is used to sedate elephants and other large animals. The Drug Enforcement Administration issued a warning about carfentanil in September 2016, saying the drug, often disguised as heroin, “has been linked to a significant number of overdose deaths.”  

Chronic pain: Pain that lasts beyond the normal time of healing and lacks the warning function of acute pain. Chronic pain may last for three months, six months or longer.

Codeine: A prescription opiate that was first derived from opium in 1832 and is used to relieve coughs and moderate pain.

Drug misuse: The use of a drug for a purpose or in a manner other than its intended prescription, such as taking a drug that was prescribed to another person or in excessive quantities.

Fentanyl: A fully synthetic opioid, 100 times more powerful than morphine. Fentanyl was developed in 1959 and is now available by prescription in a patch form to relieve severe pain. Illegal use of fentanyl powder has risen sharply in recent years, accounting for 20,100 overdose deaths in 2016, a 540 percent increase over 2013.   

Heroin: A morphine derivative introduced in 1898 as a treatment for headaches, colds and other ailments. At first, it was considered a safer alternative to morphine and was distributed widely without prescription. When addiction and abuse became serious problems, the U.S. in 1924 enacted a law making all uses of heroin illegal. However, illicit use of the drug never went away. It was responsible for 15,400 overdose deaths in 2016.

Hydrocodone: Created in Germany in 1920 and approved by the U.S. Food and Drug Administration in 1943, hydrocodone is a prescription opioid medication available in extended-release formulations for treatment of moderate to severe acute pain. 

Methadone: Methadone is a synthetic opioid that is used to treat opioid dependence by blocking withdrawal symptoms without giving the “high” of using a narcotic. Methadone maintenance programs, developed in 1964, combine counseling with daily doses of the prescription medication, dispensed in a medical setting. Methadone, created in Germany as a pain reliever during World War II, has been legal in the U.S. since 1947 and is also used to treat pain.

Morphine: Developed in 1803 and 10 times more potent than opium, morphine is a prescription opiate for treating moderate to severe acute pain.    

Narcotic: The umbrella name for opiates and opioids.  Narcotics work by attaching to receptors in the brain and sending signals that block pain, fear and tension, and create feelings of happiness and well-being. Because narcotics work in the nervous system, they are a blunt instrument for dulling pain. They slow breathing, blood pressure and heart rate, making overdoses dangerous. Narcotics are addictive.

Naloxone: Often referred to by the brand name Narcan, naloxone saves lives by reversing the effects of an opioid overdose. Approved by the FDA in 1971, it is an opioid antagonist — meaning that it blocks the effects of opioids in the central nervous system. It is available as an injection for use by health professionals and trained individuals or a nasal spray that can be used by laypeople with minimal training. Many municipalities and health care systems are pushing to make naloxone widely available. Between 1996 and 2014, the drug saved more than 26,000 lives, according to the Centers for Disease Control and Prevention.

Opiates: Natural substances, including opium and heroin, derived from the unripe seed pods of the opium poppy. Archeological evidence suggests Neanderthals used opium poppies more than 30,000 years ago. Opiates include opium derivatives morphine and codeine. Like all narcotics, opiates attach to receptors in the brain, blocking pain, fear and tension and creating feelings of happiness and well-being. They are addictive.

Opioids: Products that dull pain and produce feelings of bliss by binding to the same brain receptors as opiates, but are synthetic, meaning they do not occur naturally. They include fentanyl, methadone, oxycodone and hydrocodone. They are addictive.

Oxycodone: An opioid first produced in 1916 and available in the U.S. since the 1930s.  OxyContin is the brand name for the extended release tablets, introduced in 1996.

Percocet: The brand name of an opioid pain medication available in the U.S. since 1976 that combines the opioid pain medication oxycodone with the nonopioid pain reliever acetaminophen. An opioid medication taken together with acetaminophen results in better pain control than either medication alone, a property called synergy.

Prescription opioid overdoses: More than 16,000 people in the U.S. died of prescription opioid overdoses in 2016, according to the Centers for Disease Control and Prevention. 

Suboxone: Suboxone, which contains both the opioid buprenorphine and the opiate antagonist naloxone, was created in 2002 to treat opioid withdrawal without the abuse potential of buprenorphine alone.   

Substance use disorder: The Diagnostic and Statistical Manual of Mental Disorders began using the term substance use disorder in 2015 and stopped using the terms addiction, substance abuse and substance dependence. Symptoms of substance use disorder include intense cravings and continued use despite negative consequences.

Tramadol: A fully synthetic opioid prescription pain medication used to treat moderate to severe pain. Developed in Germany in 1962, it became available in the U.S. in 1995. The drug works on opioid receptions, resulting in lower pain, as well as other receptors, which may increase the brain’s availability of naturally occurring chemicals norepinephrine and serotonin and improve mood, concentration and/or sleep.

Vicodin: The brand name of a prescription opioid pain medication, introduced in 1978, that combines the nonopioid pain reliever acetaminophen with the opioid hydrocodone. It is a prescription medicine for moderate to severe acute pain. An opioid medication taken together with acetaminophen results in better pain control than either medication alone, a property called synergy.