Abuse of opiate-based prescription painkillers such as oxycodone and morphine peaked around 2010-2011 and now may be on the decline in the United States, according to an analysis of databases designed to track illicit use of the drugs.

New laws, programs and policies, such as prescription tracking systems and the reformulation of oxycodone to make it harder to abuse, may be combining to reverse the once-growing trend, researchers said.

"I think we're at an inflection point and we're starting to turn this steamship around," said Dr. G. Caleb Alexander, co-director of the Johns Hopkins’ Center for Drug Safety and Effectiveness, who was not involved in the research.

But he noted that there might be reason for concern because the results also suggest that a move toward cheap heroin could be a factor in bringing the prescription drug abuse rates down.

"We still have a long way to go, is how I would frame it," Alexander said.

As many as 16,651 people died from abusing such drugs in 2010 and there has been a strong push by doctors, lawmakers, regulators and drug manufacturers to reduce those numbers, he told Reuters Health.

"In a way, it would be hard to imagine things getting much worse, when the U.S. accounts for only 5 percent of the world's population and more than 80 percent of the prescription opioids consumed," he said. "More people die from prescription opioids than automobile accidents."

The new study, published in the New England Journal of Medicine, looked at data collected between 2002 and 2013 from substance-abuse treatment centers, poison centers, college students and drug-diversion investigators.

There were "large increases in the rates of opioid diversion and abuse from 2002 to 2010, but then the rates flattened or decreased from 2011 through 2013. The rate of opioid-related deaths rose and fell in a similar pattern," write the study authors, led by Dr. Richard Dart of the Rocky Mountain Poison and Drug Center at the Denver Health and Hospital Authority in Colorado.

The only gauge that didn't show a significant decline by 2013 was among college students. "College students pick stimulants a lot more than opioids. So it's a really low number, and it's hard to go down when you have a really low number," Dart told Reuters Health.

He and his colleagues also tracked heroin use and found indications that it increased significantly after development of an extended-release formulation of oxycodone made that drug, known as OxyContin, harder to abuse.

Are people shifting from prescription drug abuse to heroin?

"That's a concern, but I don't think we have the answer, Dart said. "The heroin increase started way back in 2004-05."

Both Dart and Alexander said it's impossible to pinpoint a single cause in the reduction.

There has been a leveling-off in the rate of pain prescriptions being written since 2011 and "in every state except Missouri, if a patient says they need something, you can go online and say, 'No, you just had a prescription filled a week ago.' It allows you to detect the people who are trying to trick the system," Dart said.

Another big factor in the drop may have been a crackdown in Florida. Prior to 2011, the state was notorious for having "pill mills" and pain clinics that were little more than dispensaries for pain medicines, he said. When the state closed them down, "that had a big effect. We saw immediate decreases as soon as they did that."

Dart said that, compared to other initiatives, changing the OxyContin formulation may not have had a big impact.

"It's easy for the patient to go to the doctor and say, 'I don't like the new OxyContin. Switch me to something else,'" he said.

Dart said it’s important to remember that, "This is not a disease of the indigent population or drug abusers as we typically think of them. It's a condition that a lot of employed and working people get because they get their opioids for a good reason because they had surgery, for example. Then they find out they're susceptible and get addicted. Both patients and physicians need to say, 'Do I really need this opioid?'"