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The science of opioids

Updated: Feb 23, 2021

Laura Chrisman writes on the science of opioids with help from Dr. Karilynn Dowling-McClay, an associate professor at Bill Gatton College of Pharmacy.

The human body is a chemistry lab where reactions happen constantly, but the expected results from these reactions differ when opioids are introduced. These drugs affect the central nervous system by travelling to the brain and binding to opioid receptors. Understanding what an opioid is and how it affects the body is necessary to combat opioid misuse.

Originally, the naturally occurring substances found in poppies, such as morphine and codeine, were referred to as opiates, while laboratory-made products, like oxycodone and heroin, were called opioids, according to the Drug Enforcement Administration Museum. However, “opioid” has become a collective term to describe addictive drugs.

“When someone takes that drug, it makes its way to the brain, and the drug molecule attaches to the receptor in the brain tissue,” said Karilynn Dowling-McClay, associate professor at Bill Gatton College of Pharmacy at East Tennessee State University.

Opioids are addictive because they interact with chemical signaling in the brain, and they can temporarily lessen physical and emotional pain.

“They can make people feel good, or they can make people forget what’s going on in their life that’s causing them stress or trauma,” said Dowling-McClay. “It’s very appealing to continue using them.”

Taking opioids for any length of time can have side effects. In the short term, these drugs provide pain relief, however, drowsiness and stomach problems can occur. The known long term side effects of opioids include constipation, repressed breathing, tolerance, dependence and substance abuse disorder, previously known as addiction.

“They [people taking opioids] might feel really sick if they don’t have access to their drug when they need it,” said Dowling-McClay. “Basically, the body is saying, ‘I only know how to function right if I have the drug present.’”

Tolerance is the amount of a substance needed to produce a desired effect. Gradually, the body becomes used to a substance and needs a higher dose to have a response. While tolerance is not a sign of addiction, it can lead to substance abuse problems. Dependence occurs after the drug has been in the body a long time. Physical and/or psychological signs manifest when the drug is out of the body.

According to the DEA, the Controlled Substances Act classifies drugs into five categories based on the drug’s medical uses and level of danger: Schedule I drugs have “no currently accepted medical use” and are the most dangerous while Schedule V are the least. Opioids can be found in each schedule.

The cycle of opioid misuse can be broken through prevention, treatment, and overdose reversal. Prevention involves educating people on healthy coping mechanisms; it also involves medical professionals appropriately prescribing opioids. Methadone is one medication available to treat substance abuse disorders. Although it is another opioid, it can be an effective treatment for substance abuse disorders when combined with counseling. Methadone works well because it stays in the body for long periods of time and helps reduce cravings, according to Johns Hopkins Medicine. Suboxone, also known as buprenorphine, is another treatment option. It is like methadone in that it helps to manage the side effects of withdrawal, but it is also different because it has a partial response on the opioid receptors in the brain.

“The methadone still can have stomach side effects like any other opioid, can still make people drowsy,” said Dowling-McClay.

The final step in breaking the addiction cycle is overdose reversal. This is where naloxone, better known by the brand name Narcan, comes in. Unlike methadone and Suboxone, naloxone blocks the “euphoric/sedative effects of opioids,” according to Johns Hopkins Medicine, making it possible to reverse an overdose.


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