Because of their role in initiating a calamitous opioid epidemic that has killed half a million Americans — almost as many as COVID-19, a once-in-a-century pandemic — U.S. pharmaceutical companies have been hit with an avalanche of lawsuits and criminal investigations.

And rightly so.

Big drug companies orchestrated a market for prescription opioids through false marketing claims that deceptively downplayed the risk of addiction.

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But one key player in this ongoing national disaster has so far escaped accountability: the FDA.

In 1995, the federal Food and Drug Administration gave its approval to Purdue Pharma for a powerful new opioid. OxyContin, the company claimed, would alleviate chronic pain and limit the risk of addiction through an extended-release formulation that made it harder for users to get high.

That decision, and the approval of other similar opioids, played a pivotal role in igniting the drug scourge afflicting the nation now for more than 25 years. As the Biden administration searches for a nominee for permanent FDA commissioner, it is long past time to investigate fully how the FDA failed to properly regulate opioid manufacturers or correct its devastating and scientifically unsupportable decisions. Only then can the nation have confidence a similar public health failure won’t happen again.

One person who appears consistently throughout this regulatory fiasco is Janet Woodcock, the FDA’s current acting commissioner. Woodcock was head of the FDA division that approved the initial OxyContin application in 1994 and held the position during a period in which the FDA approved a steady stream of other extended-release opioids. Woodcock has never given a persuasive accounting of how FDA policy took such as disastrous turn, nor explained the conflict of interest of key FDA officials directly involved in the approving new opioids.

Following the FDA approval of OxyContin in December 1995, other big drugmakers soon came out with their own extended-release opioids for long-term use. Within a few years, prescriptions for opioids in the United States quadrupled. So too did rates of addiction and overdose deaths. Prescription rates have since declined, but overdose deaths continue to rise, underscoring the ongoing virulence of the epidemic.

Yet it turns out the FDA never had reliable scientific evidence supporting the claim of safety and efficacy of opioids for chronic pain, according to an analysis in the New England Journal of Medicine. To test a drug that physicians would soon be prescribing to patients for months, if not years — and at far higher doses than were used in that brief clinical trial — Purdue Pharma had conducted only one adequate and well-controlled clinical trial of two weeks’ duration, according to FDA documents.

The problem with chronic pain treatment is that the longer patients remain on opioids, the greater the likelihood of tolerance and addiction. They may even become more sensitive to pain, according to the same New England Journal of Medicine analysis.

While the application was flimsy, the FDA approval was rife with conflicts. According to a 2006 Justice Department memo, investigators obtained evidence that primary FDA medical review officer, Curtis Wright, invited Purdue officials to assist in drafting the FDA response in a hotel room, away from FDA headquarters.

Early drafts indicated that OxyContin could be as easily abused as other prescription opioids. But later drafts said OxyContin’s extended-release formulation “is believed to reduce the abuse liability of the drug,” a claim that was included on the package label used by physicians to guide use of the drug. Purdue had proposed this language be included.

That claim had little scientific basis, and it turned out to be inaccurate since OxyContin soon became widely abused.

But it did square neatly with Purdue’s marketing plan to reassure physicians. Two years later, Wright joined Purdue as a senior scientist, at a salary of $379,000 a year.

In 2019, Sens. Maggie Hassan (D., N.H.) and Edward Markey (D., Mass.) wrote the FDA asking what scientific basis the agency had for approving widespread use of opioids.

Woodcock’s response was a masterpiece of bureaucratic evasion. No one, least of all Woodcock, took responsibility.

That’s not good enough. Given the enormous consequences, the FDA must explain in detail where the process went wrong and what steps the agency is taking to make sure such a disaster never occurs again.

Andrew Kolodny, a graduate of Temple University Medical School, is medical director of the Opioid Policy Research Collaborative at Brandeis University and has served as an expert witness in the national litigation over the opioid epidemic. Chris Mondics is a legal affairs journalist based in Philadelphia.