Opioids are painkillers such as oxycodone (OxyContin and Percocet) and hydrocodone (Vicodin) that are synthesized to mimic the effects of pain-relieving opiates like morphine and heroin. Despite being effective for treating acute pain, these substances pose an extremely high risk of addiction to those who take them. The overuse and abuse of addictive opioid drugs is an ongoing crisis in the United States, with opioid overdoses killing nearly 50,000 people in 2019 alone.
Scientists are uncovering new ways in which opioids affect the body, with a recent study revealing that continued use of this drug can result in chronic inflammation and a heightened sensitivity to pain. These effects may be influenced by the individual’s immune system, which produces antibodies against the medications.
"Extrapolating from previous work on opioid vaccines, we started thinking that the patient's own immune system could be responsible for some of the negative effects of long-term opioid use," said Cody J. Wenthur, who led the study. "We thought the body could be mounting an immune response and making antibodies against the drugs."
Opioids, once absorbed into the bloodstream, don’t trigger the immune system. However, they can bind to proteins in the blood, creating a bigger molecular in a process known as haptenization. Over time, the immune system produces antibodies targeted at these haptens. In the study, the researchers found such antibodies in 10 out of 19 individuals that were regularly taking prescription opioids for chronic lower back pain. "This was surprising," said Jillian Kyzer, one of the scientists involved in this work. "We saw antibody responses in people who were taking large doses for as little as 6 months."
According to Wenthur, follow-up studies will continue to build upon the team’s discovery, with the goal of mapping the prevalence of these anti-opioid antibodies in larger patient cohorts.
"The research could also be helpful in identifying efficacy biomarkers for opioid vaccines that are entering clinical trials," said Kyzer. "If our findings hold up in subsequent research, you would expect individuals with higher levels of these antibodies to be poor candidates for anti-opioid vaccine therapy."