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Rise in HCV infection rates linked to OxyContin reformulation.

PUBLIC HEALTH EXPERTS have attributed the alarming rise in hepatitis C virus (HCV) infection rates in recent years to the opioid epidemic, and a new Rand study suggests that an effort to deter opioid abuse--namely, the 2010 abuse-deterrent reformulation of OxyContin--is partly to blame.

Between 2004 and 2015, HCV infection rates in the United States nearly tripled. A closer look showed that states with above-median rates of OxyContin misuse prior to the reformulation had a 222% increase in HCV rates, compared with a 75% increase in states with below-median OxyContin misuse, said David Powell, PhD, a senior economist at Rand in Arlington, Va., and his colleagues, Abby Alpert, PhD, and Rosalie L. Pacula, PhD.

The coauthors of the report published in Health Affairs found that hepatitis C infection rates were not significantly different between the two groups of states before the reformulation (0.350 vs. 0.260). But after 2010, there were large and statistically significant differences in the rates (1.128 vs. 0.455; P less than 0.01), they wrote, noting that the above-median states experienced an additional 0.58 HCV infections per 100,000 population through 2015 relative to the below-median states).

HCV infection rates declined during the 1990s followed by a plateau beginning around 2003, then rose sharply beginning in 2010, coinciding with the introduction of the release of the abuse-deterrent formulation of OxyContin, which is one of the most commonly misused opioid analgesics, the investigators said, explaining that the reformulated version was harder to crush or dissolve.

"Prior studies have shown that, after OxyContin became more difficult to abuse, some nonmedical users of OxyContin switched to heroin (a pharmacologically similar opiate)," they noted. The investigators assessed whether the related increase in heroin use might explain the increase in HCV infections.

Using a quasi-experimental difference-in-differences approach, they examined whether states with higher exposure to the reformulated OxyContin had faster growth of HCV infection rates after the reformulations, and as a falsification exercise, they also looked at whether the nonmedical use of pain relievers other than OxyContin predicted post-reformulation HCV infection rate increases.

HCV infection rates for each calendar year from 2004 to 2015 were assessed using confirmed case reports collected by the Centers for Disease Control and Prevention, and nonmedical OxyContin use was measured using self-reported data from the National Survey on Drug Use and Health.

There was small relative increase in HCV infection rates in 2010 in the above-median OxyContin misuse states, and the gap between above- and below-median misuse states widened more rapidly from 2011 to 2013. "This striking inflection point in the trend of hepatitis C infections for high-misuse states after 2010 mimics the inflection in heroin overdoses that occurred as a result of the reformulation," they said, noting that heroin morality per 100,000 population was nearly identical in the two groups of states in the pre-reformulation period (0.859 and 0.847).

The falsification exercise looking at nonmedical use of pain relievers other than OxyContin in the two groups of states showed that after 2010 groups' rates of hepatitis C infections grew at virtually identical rates.

"Thus, the differential risk in hepatitis C infections was uniquely associated with OxyContin misuse, rather than prescription pain reliever misuse more generally," they said. "This suggests that it was the OxyContin reformulation, not other policies broadly affecting opioids, that drove much of the differential growth."

The investigators controlled for numerous other factors and cited several limitations, including the possibility that true hepatitis C infection rates might have been underestimated in the study.

Dr. Powell and Dr. Pacula received funding from the National Institute on Drug Abuse. Dr. Powell also cited funding from the Rand Alumni Impact Award.

SOURCE: Powell D et al. Health Aff. 2019;38(2):287-94.



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Author:Worcester, Sharon
Publication:Internal Medicine News
Date:Mar 1, 2019
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