By Pat Anson, PNN Editor

Anti-opioid activists have long claimed that opioid pain medication is a gateway drug to heroin, often citing a 2013 study that found about 80% of heroin users had first misused prescription opioids. The gateway drug theory soon became doctrine in the national debate over opioids.

“The connection between prescription opioid abuse and heroin use is clear, with 80% of new heroin abusers starting their opioid addiction by misusing prescription medications,” the DEA claims.

The 80% figure sounds alarming, but it is misleading. Only about 5% of people who misuse opioid medication switch to heroin, according to the National Institute of Drug Abuse. The vast majority of people who use prescription opioids responsibly never try street drugs.

A new study of heroin users in Oregon, published in the Journal of Addiction Medicine, adds some much needed context to the claim that prescription opioids are gateway drugs.

Researchers looked at a database of over 10,000 people being treated for opioid use disorder, and identified 624 individuals who started using heroin between 2015 and 2017. About half (49%) had filled a prescription for opioids in the year before heroin initiation.

Forty-nine percent having a valid opioid prescription might seem alarming too, until you look at what else the new heroin users had in common. Compared to a control group, many were already showing signs of diversion and substance abuse. They were more likely to have multiple prescribers and pharmacies, and to have prescriptions for other controlled substances, such as benzodiazepines and buprenorphine (Suboxone).

Importantly, 41% had stopped using opioid medication prior to their use of heroin; only 13% had an opioid prescription longer than 90 days; and only 7% were on high daily doses of 90 MME (morphine milligram equivalent) or more – which was about the same as the control group. This suggests that pain medication plays only a minor role, if any, on the path to heroin.

“To our knowledge, this is the first study to quantify patterns of prescription opioid (use) preceding self-reported heroin initiation,” wrote lead author Daniel Hartung, PharmD, an Associate Professor of Pharmacy at Oregon State University. “Although prescription opioid use commonly preceded self-reported heroin initiation, long-term opioid therapy was not common.”

“The take home message for me is that, in contrast to what has been purported by some individuals, the use of long-term opioids does not increase risk of using heroin,” says Dr. Lynn Webster, a PNN columnist and past president of the American Academy of Pain Medicine. “They also report that doses above 90 MME did not increase the risk of using heroin.

“This study underscores that prescription opioids are not a gateway to heroin use. The use of prescription opioids is less of a factor that leads to any drug abuse than the genetics and environment of the person who abuses opioids.” 

Hartung and his colleagues cautioned that the gateway drug theory should not be used to forcibly taper patients off opioid medication, which might lead to “unintended harms” such as overdoses.

“Although the harms of long-term opioid therapy are well-described, emerging evidence is beginning to suggest risks associated with discontinuation or disruption of long-term therapy,” they said. “There remains an urgent need to identify factors that predict transition to heroin as well as delineate the adverse sequelae of rapid or forced de-escalation of chronic opioid therapy.”