A lot has been discussed about heroin and prescription opiates as overdoses continue to rise.

But what happens inside a person’s body when they use these drugs? Why are these drugs so dangerous, and what happens during an overdose?

Drugs like heroin, Oxycodone and morphine trace their lineage back to the opium poppy, a flower plant. Opium has been used for centuries because of its pain-fighting properties.

Fentanyl, carfentinil and the like are synthetic opioids, meaning they are not naturally occurring substances but have similar effects to natural opioids, according to the Drug Policy Alliance.

Opioid use and the brain

When a person uses heroin, the opioids attach to opioid receptors throughout the body, including in the brain, gastrointestinal tract, spinal cord and other organs, according to neuroscientist Jordan Gaines-Lewis, a policy research fellow at the Pennsylvania Department of Drug and Alcohol Programs.

Opioids block pain signals from the peripheral nerves to the spinal cord or from the spinal cord to the brain, she said.

“Drugs like heroin and fentanyl have a slightly different chemical structure that gives them a higher affinity for opioid receptors than prescription opioids, which partially explains why they are much ‘stronger,’” Gaines-Lewis said.

Along with inhibiting pain, opioids can trigger a euphoric feeling through a release of dopamine.

“Opioids activate a part of the brain called the ventral tegmental area,” she said.

This causes dopamine to be released into the nucleus accumbens - major component in the brain’s reward circuit, according to the National Institute of Drug Abuse.

This rewarding signal can motivate some people to continue seeking out the drug, Gaines-Lewis said.

“Dopamine release in the nucleus accumbens is also involved in strengthening associations between drug-taking and external stimuli,” Gaines-Lewis said. “For instance, if you only use heroin in your bedroom, being in your bedroom may become a stimulus that causes you to crave the drug.”

As people continue to use opioids, the receptors become less responsive to the drug, requiring the person to use more of the drug to release the same amount of dopamine and get the same effect, she said.

This can lead to people using not to get “high,” but rather to avoid the bottoming and “lows” associated with withdrawal.

“(T)hey need it just to function every day,” Gaines-Lewis said.


One area of the brain where opioid receptors are activated is on the brainstem.

The brainstem controls many of the body’s automatic functions like breathing and causing the heart to beat. When opioid receptors are activated in the brainstem, breathing becomes slow and irregular, and blood pressure decreases, Gaines-Lewis said.

The effects to breathing can lead to hypoxia, which is oxygen depletion to the body tissue, she said. All of this together can lead to a person losing consciousness and, in some cases, to death.

Gaines-Lewis said the opioid reversing drug naloxone works by causing the opioids in a person’s system to compete with naloxone for space on the opioid receptors. She said naloxone has a high affinity for opioid receptors, making it difficult for opioids to attach, which counteracts the overdose.

“I think one of the biggest misconceptions is that having naloxone on hand gives people with substance-use disorder a ‘safety net,’ or peace of mind that they can keep using opioids because a friend, family member or EMS will always be around to save them,” Gaines-Lewis said. “The research simply doesn’t corroborate this.”

Gaines-Lewis said that recovery from long-term opioid use is possible, but the process is different for every person.

She said people typically need to go through a process of detoxification, which treats the physical symptoms of withdrawal, followed by inpatient or outpatient treatment, which includes medical care, counseling and aftercare planning.

Gaines-Lewis said many people can also benefit from programs like pain or stress management, recovery houses, 12-step programs or occupational, social, educational or vocational services.

Medication-assisted treatment, with drugs like methadone, Vivitrol or buprenorphine, can also help a person abstain from illicit drug use by blocking the symptoms of withdrawal or eliminating the euphoric “high” feeling, she said.

Email Joshua Vaughn at jvaughn@cumberlink.com. Follow him on Twitter at @Sentinel_Vaughn.