New research from the University of California San Diego warns that taking antibiotic medications alongside powerful opioids may increase an individual’s risk of opioid abuse and addiction. According to the researchers’ findings, published in the journal eNeuro on April 27, the drug combination can cause changes in the body’s microbiome, possibly affecting the way the brain responds to opioid drugs and increasing the risk of addiction. Opioids are a class of drugs that include powerful prescription painkillers like oxycodone, hydrocodone, tramadol and fentanyl and illegal drugs like heroin. The United States is currently in the midst of an opioid epidemic and studies like this can help raise awareness for those at the greatest risk for opioid abuse and addiction.
According to the researchers in this new study, there are many different factors that play a role in the “initiation, escalation and relapse of drug use,” including genetics, behavior and the environment, but there is one factor that may play a more significant role than previously thought: the gut microbiome. Believe it or not, the bacteria in the gut has an impact on brain health and also has a part in a wide variety of brain disorders, including drug addiction. The study authors note that “One aspect of opioid addiction that has yet to be fully examined is the effects of alterations of the microbiome and gut-brain axis signaling on central nervous system activity during opioid intoxication and withdrawal.”
Opioid abuse is a national health crisis, affecting more than two million Americans. The U.S. Centers for Disease Control and Prevention (CDC) report that 130 Americans die every day from an opioid overdose, including prescription and illicit opioids. Doctors often prescribe antibiotics and opioids together after surgery to prevention infection and treat pain, and while antibiotics are useful in preventing surgical site infections, they also kill the good bacteria in the gut microbiome, which can have an adverse impact on brain health. Opioid painkillers account for 70% of all overdose deaths in the United States and experts say that the drugs are largely overprescribed in cases without a documented pain diagnosis. According to a 2019 analysis of surgeons’ prescribing habits, many doctors are quick to write prescriptions for opioid drugs, even for surgeries that cause most patients relatively little pain.
In an effort to examine the effect of antibiotic use on opioid addiction, given the prevalence of the drug combination, the researchers in the eNeuro study administered antibiotics to rats for two weeks, effectively depleting their gut microbiome, and then gave them oxycodone. Oxycodone is an opioid painkiller that carries a high risk for addiction and dependence. The painkiller is commonly used to treat moderate to severe pain and works in the brain to change how the body feels and responds to pain. What the researchers found in this study is that, compared to the rats that only received oxycodone, the rats taking both drugs exhibited significant changes in how their brains responded to opioids.
Based on their findings, the researchers concluded that the rats taking both antibiotics and opioids experienced altered opioid sensitivity in brain areas implicated in addiction. They found that the depleted gut microbiome intensified the effects of opioid intoxication and diminished the effects of withdrawal, which they note can increase the risk of drug abuse. Users who experience fewer withdrawal symptoms may not recognize the fact that they are going through withdrawal or may fail to see the disadvantages of continued use.
The findings of this study support the conclusion that changes in gut bacteria due to antibiotic use combined with opioid use may influence brain health and play a role in certain brain disorders, including addiction. While these results don’t necessarily prove a cause-and-effect relationship, the researchers note that they “represent an important advance in our understanding of the impact of the gut-brain axis on neuronal recruitment in different drug states and how the microbiome may play a role in opioid use and dependence.”