At a substance abuse forum in Boston, Hillary Clinton touted her $10 billion plan to tackle drug and alcohol addiction in the country, from pouring more resources into treatment programs to pushing for tougher federal regulation of prescription painkillers.

But the Democratic presidential candidate also took a moment to chide federal regulators over a controversial recent decision: The Food and Drug Administration's approval this summer of the narcotic pain reliever OxyContin for certain children ages 11 to 16.

"I am very concerned that the FDA has approved a form of opioids for children, and I find that absolutely incomprehensible," Clinton told the Boston audience on Thursday.

She isn't alone.

The agency's August decision triggered a fierce backlash on social media, with people accusing FDA of acting irresponsibly and putting the interests of OxyContin’s manufacturer, Purdue Pharma, ahead of the welfare of children. Sen. Joe Manchin III (D-W.Va.), whose state has been battered by the epidemic of prescription drug and heroin abuse, wrote that the FDA “should be absolutely ashamed of itself for this reckless act."

Activists such as Andrew Kolodny, a New York psychiatrist and director of Physicians for Responsible Opioid Prescribing, said the FDA failed to weigh the heightened risk of addiction in young people and expressed concerns that Purdue would use the recent approval to market the drug for use in more children -- a claim the company has denied.

Top FDA officials have stood by the decision, as have some pediatric pain specialists and parents who have had children with cancer or other painful conditions.

For starters, they say the approval of OxyContin, an extended-release form of the opioid painkiller oxycodone, applies only to a small subset of children who require “daily, round-the-clock, long-term” pain relief that can’t be treated adequately with other medications. They noted that doctors already had the ability to prescribe the drug "off label" in children -- and that they often do in young patients dealing with terminal cancer, major surgeries and other serious conditions. And they said the move was intended to give doctors better guidelines about how to use OxyContin safely in pediatric patients.

“We understand there is a terrible problem with opioid abuse and addiction,” Janet Woodcock, director of FDA’s Center for Drug Evaluation and Research, told the Post last month. “But this is about evidence-based medicine for children — seriously ill children who are suffering pain.”

Still, as Clinton's comments Thursday underscore, it's a topic that generates intense passion on both sides. It's also a slice of a broader, thorny debate about the heroin and prescription painkiller epidemic, and about what the federal government -- or anyone -- can do to combat a problem that continues to kill thousands of Americans each year.