Opioid addiction remains an alarming epidemic in the United States — in fact, it may even be getting worse. The National Institute on Drug Abuse estimated that there are approximately 2.1 million people in the U.S. who have substance abuse issues related to prescribed opioids and another 467,000 who are addicted to heroin.

In 2016, more than 63,000 people died from drug overdoses, and 42,000 were related to opioids. That means there are now more opioid addiction-related deaths in the United States than breast cancer deaths.

Providing treatment for those struggling with opioid use disorder to prevent overdose or even death remains the primary focus of healthcare professionals. Between 1997 and 2011, opiate addiction treatment had grown by an astonishing 900 percent.

Partial agonists such as buprenorphine, sold under the brand name Subutex, are prescribed to treat opioid addiction and represent the latest advance in medication-assisted treatment. Unlike methadone, which is classified as a Schedule II substance under the Controlled Substances Act, buprenorphine is classified as a Schedule III substance because its potential for abuse is lower.

By producing enough agonist, patients who have become addicted to other opioids are able to discontinue abuse by taking buprenorphine with minimal withdrawal side effects. Buprenorphine has a slow onset and a long half-life of 24 to 60 hours. However, buprenorphine use may pose issues for some patients.

A new study at the UT Medical Center found that buprenorphine impairs the ability of obese mice to vary their breathing, which could translate into causing breathing problems in some obese patients since the ability to vary breathing helps people achieve tasks such as climbing stairs and responding to challenges such as disease and surgical stress.

Ralph Lydic, Robert H. Cole Endowed Professor of Neuroscience in the UT Department of Psychology and the Department of Anesthesiology at UT Medical Center, and a team of scientists studied both mice of normal weight and diet-induced obese mice. Earlier studies in humans have shown a greater risk for respiratory failure caused by opioids among obese female patients.

The results of this study support the interpretation that leptin status, but not body weight or sex, contributed to the buprenorphine-induced decrease in minute ventilation, which is important because normal respiratory variability is essential for martialing a compensatory response to ventilatory challenges imposed by disease, obesity and surgical stress.

Although buprenorphine received approval from the Food and Drug Administration in 2002, only now, in 2018, has this side effect been discovered in mice, indicating the need to support clinical research. Lydic and his team plan to conduct more studies to determine the brain regions and neurotransmitters involved in buprenorphine's depression of respiratory variability.