A reformulation of OxyContin that makes it harder to abuse has curtailed the drug's illicit use. But some 25 percent of drug abusers entering rehab said they still abused the prescription painkiller despite package labeling that emphasizes its abuse-deterrent properties, new research indicates.

The study, by researchers at Washington University School of Medicine in St. Louis, is published March 11 in JAMA Psychiatry.

Surveying almost 11,000 drug users at 150 drug-treatment facilities in 48 states, the researchers found that an abuse-deterrent formulation of the prescription drug OxyContin was successful in getting abusers and addicts to stop using the drug, but only to a point.

"We found that the abuse-deterrent formulation was useful as a first line of defense," said senior investigator Theodore J. Cicero, PhD, a professor of neuropharmacology in psychiatry. "OxyContin abuse in people seeking treatment declined, but that decline slowed after a while. And during that same time period, heroin use increased dramatically."

The original formulation of OxyContin contained high levels of the pain-killing drug oxycodone. It was designed so that small amounts of the drug were released over a long period of time. However, abusers in pursuit of an intense high found they could crush the pills and snort the powder, or dissolve the pills in liquid and then inject the drug.

To discourage abuse, the newer formulation of OxyContin was designed to make it harder to crush or dissolve the pills.

The abuse-deterrent formulation was introduced in 2010 at a time when 45 percent of study participants entering drug treatment reported they had used OxyContin to get high at least once in the previous 30 days. Two years later, the percentage of those who got high with the abuse-deterrent form of the drug in the month before entering a treatment center had fallen to 26 percent.

These abusers continued to use OxyContin to get high by either taking the drug orally or finding new ways to snort or inject it.

Perhaps even more worrisome, almost half of the drug abusers surveyed in 2014 reported they had used heroin in the 30 days before they entered treatment.

"Some people found ways to get around the abuse-deterrent formulation so that they could snort or inject it, and others simply swallowed the pills," Cicero explained. "But many people switched to heroin, and that's a major concern."

Cicero, also vice chairman for research in the Department of Psychiatry, explained that of those who had stopped using OxyContin and switched to another drug, 70 percent started using heroin instead. Many said they made that switch for economic reasons.

"A few years ago when we did interviews with people in treatment, many would tell us that although they were addicts, at least they weren't using heroin," he said. "But now, many tell us that a prescription opioid might run $20 to $30 per tablet while heroin might only cost about $10."

In addition, he said, many of the people who sell heroin aren't quite as frightening as they once seemed. Addicts no longer have to find dealers in dark alleys in rough neighborhoods. It has become easy to find heroin virtually anywhere, including suburban and rural areas.

"Some people have come to see it as a cost-effective method of getting high," Cicero said. "If they can tolerate the intravenous injection and overcome their reluctance to give themselves a shot, many of the people in our study said it was a fairly simple decision and that heroin now represents a cheaper, more attractive alternative."

Limiting access to a prescription drug by making it harder to abuse does not change the demand side of the drug abuse equation, he said. People who want to get high find ways to continue doing so.

"The newer formulations are less attractive to abusers, but the reality is -- and our data demonstrate this quite clearly -- it's naïve to think that by making an abuse-deterrent pill we can eliminate drug abuse," he said. "There are people who will continue to use, no matter what the drug makers do, and until we focus more on why people use these drugs, we won't be able to solve this problem."

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The data were collected as part of the SKIP (Survey of Key Informants' Patients) program, a component of the RADARS (Researched Abuse, Diversion and Addiction-Related Surveillance) system, funded through an unrestricted research grant sponsored by the Denver Health and Hospital Authority, which collects subscription fees from 14 pharmaceutical firms. The researchers also were supported by private university funds.

Cicero TJ, Ellis MS. Abuse-deterrent formulations and the prescription opioid abuse epidemic in the United States. JAMA Psychiatry, published online March 11, 2015. doi:10.1001/jamapsychiatry.2014.3043

Washington University School of Medicine's 2,100 employed and volunteer faculty physicians also are the medical staff of Barnes-Jewish and St. Louis Children's hospitals. The School of Medicine is one of the leading medical research, teaching and patient-care institutions in the nation, currently ranked sixth in the nation by U.S. News & World Report. Through its affiliations with Barnes-Jewish and St. Louis Children's hospitals, the School of Medicine is linked to BJC HealthCare.