This is your brain on opioids

In this series, Yahoo News takes a closer look at the current opioid epidemic, its roots and demographics, the increasing acceptance of medication-assisted treatment as a supplement to 12-step programs and the remaining obstacles to combating widespread addiction. This series also highlights ways in which the current crisis is unexpectedly forcing a larger shift toward treating addiction more like other chronic illnesses. 

Before discussing different methods for treating opioid addiction, it’s important to understand how drugs like heroin, OxyContin, Percocet and other prescription pain medications actually affect the brain.

They work on opioid receptors in the brain, which ordinarily are activated by a class of neurotransmitters called endorphins. Heroin and other opioid drugs flood the brain’s opioid receptors, creating a high or euphoric feeling.

When a person uses these kinds of drugs regularly, the number of opioid receptors in his or her brain increases to the point where natural endorphins are no longer capable of stimulating them. The more opioid receptors a person has, the more opioid drugs are needed to get high and, eventually, to simply feel normal. This is called building a tolerance.

When not all opioid receptors are activated, it can create feelings of anxiety, depression and physical pain or illness — what’s called withdrawal. Once someone has developed a tolerance for opioids, he or she requires an increasing amount of drugs to avoid the sensation of withdrawal.

One of the effects of opioid drugs on the body is respiratory depression, or slowed breathing. Overdosing on opioids can be fatal because too much of the drug can reduce the number of breaths a person takes, to the point that he or she stops breathing altogether.

Between 2000 and 2014, the rate of opioid-related overdose deaths in the U.S. increased by 200 percent — more than any other kind of drug overdose fatalities, such as those from cocaine or alcohol. While overdose is always a possibility with regular opioid use, the risk of fatal overdose is particularly high among opioid addicts who have recently checked out of rehab.

Relapse is often a regular part of the addiction recovery process, but for those addicted to opioids, relapse can be especially deadly. That’s because tolerance quickly returns to normal after detox but the psychological dependence on drugs is not so easy to extinguish. The craving, and the risk of relapse, is typically strongest immediately after recovery, but with a significantly diminished tolerance, the same dosage that once got a person high could now be fatal.

Read more from this series:

—How buprenorphine, or ‘bupe,’ changed opioid addiction treatment
 
—Abstinence vs. medication-assisted treatment: Traditional 12-step programs embrace a new model 
 
—It’s easier to get a prescription for drugs that cause opioid addiction than those proven to treat it
 
—The menace in the medicine cabinet: The opioid epidemic’s pharmaceutical roots
 
—The rise of Narcan, the life-saving opioid antidote that can stop an overdose in its tracks 
 
—Why the new face of opioid addiction calls for a new approach to treatment

—Facing an epidemic of overdoses, Obama rejects governors' proposal to limit painkiller prescriptions