Purdue Pharma’s 2010 release of a version of OxyContin formulated to deter abuse wound up fueling the spread of hepatitis C virus (HCV) as people with opioid use disorder sought alternatives to misusing prescription painkillers.

In their past research, researchers at RAND Corporation established that the 2010 OxyContin reformulation, which made the pill difficult to crush or dissolve, led some people taking the painkillers for nonmedical reasons to adopt injecting heroin as an alternative. The result was a rise in heroin overdoses.

Publishing their findings of a follow-up study in Health Affairs, the RAND research team analyzed data on HCV infections in each U.S. state between 2004 and 2015. They found that in states that had rates of OxyContin misuse above the national median prior to 2010, hep C infections rose by 3.22-fold during the period following that year. As for the states that had OxyContin misuse rates below the national median, they saw a more moderate 1.75-fold increase in hep C infections after the drug was reformulated.

Prior to 2010, there was almost no difference in the hep C infection rates between those states with below-median misuse of OxyContin versus those with a misuse rate of the drug that was above the median.

“Even with recent advancements in the treatment for hepatitis C, the dramatic increase in infections represents a substantial public health concern that can have tremendous long-term costs if infected people are not identified and treated,” Rosalie Liccardo Pacula, a study coauthor and the codirector of the RAND Opioid Policy Tools and Information Center and the RAND Drug Policy Research Center, said in a press release.

Injection drug use, specifically the sharing of unsterilized drug paraphernalia, also drives HIV transmission, although that virus transmits somewhat less readily than HCV among people who inject drugs. After nearly two decades of declines in the national rate of HIV transmission via injection drug use, the rate has apparently begun to rise again as a result of the opioid epidemic.

“It is important that strategies that limit the supply of abusable prescription opioids are paired with polices to ease the harms associated with switching to illicit drugs, such as improved access to drug treatment and increased efforts to identify and treat diseases associated with injection drug use,” Pacula said in the same release.

To read a press release about the study, click here.