A version of this story was published in The Washington Post.

As the U.S. Senate Finance Committee launched an investigation Tuesday into makers of narcotic painkillers and groups that champion them, a leading pain advocacy organization said it was dissolving "due to irreparable economic circumstances."

The American Pain Foundation, which described itself as the nation’s largest organization for pain patients, was the focus of a December investigation by ProPublica in The Washington Post that detailed its close ties to drugmakers.

The group received 90 percent of its $5 million in funding in 2010 from the drug and medical-device industry, ProPublica found, and its guides for patients, journalists and policymakers had played down the risks associated with opioid painkillers while exaggerating the benefits.

It is unclear whether the group's announcement Tuesday evening — that it would "cease to exist, effective immediately" — was related to letters sent earlier in the day from Sens. Max Baucus, D-Mont., the finance panel chairman, and Charles Grassley, R-Iowa, to the foundation, drug companies and others.

In the letters, the senators cited an "an epidemic of accidental deaths and addiction resulting from the increased sale and use of powerful narcotic painkillers," including popular brand names like Oxycontin, Vicodin and Opana.

Growing evidence, they wrote, suggests that drug companies "may be responsible, at least in part, for this epidemic by promoting misleading information about the drugs' safety and effectiveness."

The American Pain Foundation's website carried a statement Tuesday night saying its board had voted May 3 to dissolve the organization because it couldn't stay "operational." The foundation did not respond to requests for comment Tuesday.

The senators are targeting a who's who of the pain industry, seeking extensive records and correspondence documenting the links, financial and otherwise, between them and the makers of the top-prescribed narcotic painkillers.

Letters went to three pharmaceutical companies, Purdue Pharma, Endo Pharmaceuticals and Johnson & Johnson, as well as five groups that support pain patients, physicians or research: the American Pain Foundation, American Academy of Pain Medicine, American Pain Society, Wisconsin Pain & Policy Studies Group, and the Center for Practical Bioethics.

The Federation of State Medical Boards, the trade group for agencies that license doctors, received a letter, as did The Joint Commission, an independent nonprofit that accredits hospitals nationwide and made pain management a national priority in 2001.

A report by the U.S. Government Accountability Office in 2003 noted that the commission partnered with Purdue Pharma, the maker of Oxycontin, to distribute pain educational materials nationwide. The committee's letter to Purdue noted that the company pleaded guilty in 2007 to federal criminal charges that it misled regulators, physicians and consumers about Oxycontin's risk of addiction.

The senators requested payment information since 1997 to 10 groups and eight people, including two doctors featured in ProPublica's December report. They asked about any influence the companies had on a 2004 pain guide for physicians that was distributed by the Federation of State Medical Boards; on the American Pain Society's guidelines; and on the American Pain Foundation's Military/Veterans Pain Initiative.

In addition to citing ProPublica's work, the letters also mention the reporting of the Milwaukee Journal Sentinel and MedPage Today.

Patients in serious pain need access to opioids, the senators wrote, but drugmakers and health-care groups "must distribute accurate information about these drugs in order to prevent improper use and diversion to drug abusers."

"The problem of opioid abuse is bad and getting worse," Sen. Grassley said in a statement. "Something has to change."

"When it comes to these highly addictive painkillers, improper relationships between pharmaceutical companies and the organizations that promote their drugs can put lives at risk," Baucus said in a prepared statement.

Dr. Andrew Kolodny, chairman of psychiatry at Maimonides Medical Center in Brooklyn, N.Y., and president of Physicians for Responsible Opioid Prescribing, applauded the investigation.

"These groups, these pain organizations … helped usher in an epidemic that's killed 100,000 people by promoting aggressive use of opioids," Kolodny said. "What makes this especially disturbing is that despite overwhelming evidence that their effort created a public health crisis, they're continuing to minimize the risk of addiction."

Concerns about the overuse and abuse of painkillers have intensified in recent years. As sales of the powerful drugs have boomed — rising 300 percent since 1999 — so, too, have overdose deaths. Opioids were involved in 14,800 overdose deaths in 2008, more than cocaine and heroin combined, according to the U.S. Centers for Disease Control and Prevention.

In 2009, the use and misuse of the drugs were cited in more than 475,000 emergency department visits, nearly doubling the 2004 number, the CDC said.

Pain doctors and patient groups say that while drug overdoses are a legitimate concern, only a small percentage of deaths involves patients who receive them from their doctors. Most deaths involve illicitly obtained drugs, statistics show.

The groups also say that patients' risk is low if they do not have addictive personalities, and that any restrictions should not punish patients who suffer from serious pain.

In recent weeks, two articles in medical journals have documented different aspects of abuse.

According to a paper published online this week by the Archives of Pediatrics & Adolescent Medicine, one of every eight high school seniors surveyed said they had used prescription opioids for nonmedical reasons.

A paper released last month by The Journal of the American Medical Association found that the rate of newborns diagnosed with drug withdrawal jumped threefold from 2000 to 2009. And the rate of mothers using opioids at the time of delivery was five times higher in 2009. (Not all babies born to mothers using the drugs exhibit signs of withdrawal.)

Janssen Pharmaceuticals, a Johnson & Johnson subsidiary that makes the painkiller Nucynta, said in a statement that it "is committed to the responsible prescribing and appropriate use of opioid pain medications" and has supported educational websites about safe use.

The company is reviewing the senators' letter and "will work with them to fulfill their request for information," spokesman Mark Wolfe said via email.

Purdue Pharma acknowledged in a statement that it had received the letter, was reviewing it and looked forward to "cooperating with the committee on this matter."

Endo did not return a request for comment. A spokeswoman for The Joint Commission said the group had just received the senators' letter and had no comment yet. The Federation of State Medical Boards responded but did not offer immediate comment.