Also, in a rare move, three executives of Purdue Pharma — President Michael Friedman, top lawyer Howard Udell and former medical director Dr. Paul Goldenheim — pleaded guilty Thursday to misbranding charges, a criminal violation.

They agreed to pay a total of $34.5 million in fines.

The fines will be distributed to state and federal law enforcement agencies, the federal government, federal and state Medicaid programs, a Virginia prescription monitoring program and individuals who had sued the company.

The plea agreement settled a national case and came two days after the company agreed to pay $19.5 million to 26 states and the District of Columbia to settle complaints that it encouraged physicians to overprescribe OxyContin.

"With its OxyContin, Purdue unleashed a highly abusable, addictive, and potentially dangerous drug on an unsuspecting and unknowing public," U.S. Attorney John Brownlee said.

"For these misrepresentations and crimes, Purdue and its executives have been brought to justice."

Purdue spokesman James Heins objected to any suggestion of ties between the plea agreement and the abuse of OxyContin. "We promoted the medicine only to health care professionals, not to consumers," he said in a statement.

Purdue Pharma said it accepted responsibility for its employees' actions and has taken steps to ensure "similar events" do not occur again.

OxyContin is a powerful, long-acting narcotic that provides relief of serious pain for up to 12 hours. Initially, Purdue Pharma contended that OxyContin, because of its time-release formulation, posed a lower threat of abuse and addiction to patients than traditional, shorter acting painkillers like Percocet or Vicodin.

That claim became the lynchpin of the most aggressive marketing campaign ever undertaken by a pharmaceutical company for such a drug. Just a few years after its debut in 1996, annual sales hit $1 billion.

Purdue Pharma heavily promoted OxyContin to doctors who had little training in the treatment of serious pain or in recognizing signs of drug abuse in patients.

But both experienced drug abusers and novices, including teenagers, soon discovered that chewing an OxyContin tablet or crushing one and then snorting the powder or injecting it with a needle produced a high as powerful as heroin.

By 2000, several parts of the U.S. began to see skyrocketing rates of addiction and crime related to the drug's use.

In a proceeding Thursday morning in U.S. District Court, both Purdue Pharma and those executives acknowledged that the company fraudulently marketed OxyContin for six years as a drug that was less prone to abuse as well as one that also had fewer narcotic side effects.

Federal officials said that internal Purdue Pharma documents show that company officials recognized even before the drug was marketed that they would face stiff resistance from doctors concerned about OxyContin's potential to be abused.

As a result, company officials developed a fraudulent marketing campaign to promote OxyContin as a time-released drug less prone to such problems.