More from the paper:

• The Food and Drug Administration "has promoted the development of abuse-deterrent opioids ... Despite the enthusiasm for [abuse-deterrent formulations], our results suggest that the benefits of the reformulation are easily undone when there are readily-available substitutes."

The FDA's response: “The lowest cost substitute for individuals suffering from substance use disorder is often street drugs like heroin, or increasingly synthetic fentanyl products being shipped into the U.S. from other countries. Abuse deterrent formulations are not a silver bullet solution to the opioid crisis," FDA Commissioner Scott Gottlieb said.

• This, he said, is why the agency has been pushing so hard for more funding and resources dedicated to its work at international mail facilities, as illegal opioids increasingly arrive to the U.S. in the mail.

Data note: While the authors argue that there "appears to have been one-for-one substitution of heroin deaths for opioid deaths" after the 2010 reformulation, the raw numbers seem to show more fluctuation. I asked the researchers why:

• "From 2004-August 2010, you get a relatively steady increase. Then from August 2010 through the end of 2013, things are flat or decreasing slightly," said Ethan Lieber, an economics professor at the University of Notre Dame.
• "We do see a rise in opioid death rates starting at the end of 2013, but that's due to a separate event, the adulteration of opioids and heroin with fentanyl (which makes using these things far more dangerous) ... Prior to fentanyl, opioid death rates appeared to have leveled off."