(CNN) - Experts say the United States is in the throes of an opioid epidemic, as more than two million Americans have become dependent on or abused prescription pain pills and street drugs.
Opioids are drugs formulated to replicate the pain-reducing properties of opium. They include both legal painkillers like morphine, oxycodone, or hydrocodone prescribed by doctors for acute or chronic pain, as well as illegal drugs like heroin or illicitly made fentanyl. The word "opioid" is derived from the word "opium."
Opioids bind to receptors in the brain and spinal cord, disrupting pain signals. They also activate the reward areas of the brain by releasing the hormone dopamine, creating a feeling of euphoria or a "high."
During 2017, there were more than 72,000 overdose deaths in the United States, including 49,068 that involved an opioid, according to a provisional CDC count. More than 130 people died every day from opioid-related drug overdoses in 2016 and 2017, according to the US Department of Health & Human Services (HHS).
The number of opioid prescriptions dispensed by doctors steadily increased from 112 million prescriptions in 1992 to a peak of 282 million in 2012, according to the market research firm IMS Health. The number of prescriptions dispensed has since declined, falling to 236 million in 2016. The number dropped 10.2% in 2017 from 2016, according to IQVIA (formerly IMS Health).
Opioids such as morphine and codeine are naturally derived from opium poppy plants more commonly grown in Asia, Central America and South America.
~ Hydrocodone (Vicodin)
~ Oxycodone (Percocet, OxyContin)
~ Hydromorphone (Dilaudid)
Hydrocodone and oxycodone are semi-synthetic opioids, manufactured in labs with natural and synthetic ingredients. Between 2007 and 2016, the most widely prescribed opioid was hydrocodone (Vicodin). In 2016, 6.2 billion hydrocodone pills were distributed nationwide. The second most prevalent opioid was oxycodone (Percocet). In 2016, 5 billion oxycodone tablets were distributed in the United States.
The International Narcotics Control Board reported that in 2015, Americans represented about 99.7% of the world's hydrocodone consumption.
Heroin is an illegal drug synthesized from morphine.
~ Meperidine (Demerol)
~ Levorphanol (Levo-Dromoran)
Fentanyl is a fully synthetic opioid, originally developed as a powerful anesthetic for surgery. It is also administered to alleviate severe pain associated with terminal illnesses like cancer. The drug is up to 100 times more powerful than morphine. Just a small dose can be deadly. Illicitly produced fentanyl has been a driving factor in the number of overdose deaths in recent years.
Methadone is another fully synthetic opioid. It is commonly dispensed to recovering heroin addicts to relieve the symptoms of withdrawal.
Carfentanil is 10,000 times more powerful than morphine and was created to tranquilize elephants.