Two million Americans were dependent on prescription opioids in 2014, when the most recent data was available, federal statistics show.
Opioids are drugs that reduce pain by switching off pain receptors in the brain.
They are among the most widely prescribed drugs in the United States, the CDC says, fueling an epidemic that starts at the doctor's office and spills onto the streets.
What drugs are considered opioids?
Prescription opioids include painkillers such as morphine, oxycodone and hydrocodone.
Others, such as the synthetic pain reliever fentanyl, are used for patients suffering from advanced terminal illness such as cancer.
Why are opioids dangerous?
They all produce an increased pain tolerance and a sense of euphoria. All opioids trigger a craving when the drug is absent. Individuals who use or take opioids build a tolerance, so they need higher doses for the same effect over time.
Many heroin users first became addicted to prescription pills. The heroin is a cheaper alternative, about one-tenth the price, when they can no longer get pills.
There's a ripple effect around heroin use: In addition to the risk of death and overdoses, heroin addiction comes with a whole new set of problems, such as infections of the heart lining and valves, and rheumatological diseases.
Heroin users are also more likely to suffer from HIV, hepatitis and other blood diseases because users might inject the drug with a shared needle.
How bad are opioid overdoses in the U.S.?
The statistics are grim.
See the latest news and share your comments with CNN Health on Facebook and Twitter.
Every 19 minutes, someone dies from an accidental overdose, the CDC reports.
Most drug overdose deaths -- at least six out of 10 -- involve an opioid, federal statistics show.
CNN's Nadia Kounang and Dr. Sanjay Gupta contributed to this report
Source ↔ Download Free Music