WASHINGTON -- NFL teams frequently violated federal laws that govern how they should store, track and distribute prescription painkillers, according to sealed court documents obtained by The Washington Post.

The court documents are part of an ongoing federal lawsuit, filed by more than 1,800 former NFL players, and include testimony from team doctors and trainers.

The players, who are suing the NFL in U.S. District Court in Northern California, claim they suffered long-term health problems as a result of the improper and deceptive drug-distribution practices by NFL teams, according to the court filing.

"Every doctor deposed so far ... has testified that they violated one or more" federal drug law and regulation "while serving in their capacity as a team doctor," the court filing states.

Anthony Yates, the Pittsburgh Steelers' team doctor and past president of the NFL Physicians Society, testified in a deposition that "a majority of clubs as of 2010 had trainers controlling and handling prescription medications and controlled substances when they should not have," according to the Post report.

Bud Carpenter, the Buffalo Bills' longtime trainer, "admitted under oath that he witnessed team doctors give players injections of prescription medications without telling them what the drug was they were receiving or its side effects. ... He further testified that doctors provided prescription medications at places other than where they were allowed to do so in violation of federal and state laws," according to the court filing reviewed by the Post.

The Drug Enforcement Administration has clear guidelines on how doctors should store, transport and distribute prescription painkillers, which are considered controlled substances.

But the documents reviewed by the Post suggest teams had a "cavalier attitude" toward those federal guidelines.

In August 2009, for example, Cincinnati Bengals head trainer Paul Sparling wrote in an email: "Can you have your office fax a copy of your DEA certificate to me? I need it for my records when the NFL 'pill counters' come to see if we are doing things right. Don't worry, I'm pretty good at keeping them off the trail!"

Sparling was not made available to the Post for comment and did not respond to questions from the newspaper about his 2010 email.

"The documents, emails and testimony referenced in the complaint are the tip of the iceberg," lead plaintiffs' attorney Steve Silverman said.

The NFL Players Association, which is not a plaintiff in the federal case, said in a statement Friday that the documents were "cause for our continued concern and vigilance for holding the League accountable to its obligations. We will monitor this case closely and take all steps necessary to ensure the health and safety of our players."

NFL teams frequently violated federal laws regarding prescription painkillers, according to court documents obtained by the Washington Post. Rich Graessle/Icon Sportswire

In January 2011, Outside the Lines ran a series of reports on painkiller misuse by former NFL players. The central component of that reporting was a first-of-its-kind study of painkiller use by retired NFL players.

The study, funded by ESPN and the National Institute on Drug Abuse, a division of the U.S. Department of Health and Human Services, was published in the peer-reviewed journal Drug and Alcohol Dependence.

Researchers from the School of Medicine at Washington University in St. Louis interviewed 644 retired NFL players, asking them extensive questions about their use and misuse of prescription painkillers, both as active players and in their present lives.

The study found that retired NFL players misuse opioid pain medications at a rate more than four times that of the general population and suggested that occurred because players misused the drugs during their NFL careers.

Other key findings from the study:

• Of the retired players, 52 percent said they used prescription pain medication during their playing days. Of those, 71 percent said they misused the drugs then, and 15 percent of the misusers acknowledged misusing the medication within the past 30 days.

• Those who misused prescription painkillers while playing were three times more likely to misuse the drugs after their careers than those who used the pills as prescribed while playing.

• Of the retired players, 63 percent who used prescription pain pills while playing obtained the medications from a nonmedical source, such as a teammate, coach, trainer, family member, dealer or the internet.

Several retired NFL players told researchers and Outside the Lines at the time that it was commonplace for trainers to hand out prescription pain pills. Under the law, only a doctor with the authority to write prescriptions can distribute controlled substances such as Vicodin and OxyContin. While it's illegal for team doctors to transport and distribute medications outside of the states where they have the authority to prescribe the painkillers, several retired players told Outside the Lines that, too, was a common practice.

The court filing, reviewed by the Post, reveals that NFL teams "dispensed painkillers and prescription-strength anti-inflammatories in numbers far beyond anything previously acknowledged or made public."

Almost 8,000 doses of nonsteroidal anti-inflammatory drugs and controlled medications were prescribed to players in the 2012 calendar year, according to an internal document from NFL medical adviser Lawrence Brown obtained by the Post.

Those numbers could average out to about six to seven pain pills or injections a week per player over the course of a typical NFL season, according to the report.

"It sounds like an incredible amount of intervention with some pretty risky drugs, some of which, in the case of Vicodin, have a high addiction potential," Arthur Caplan, director of the Division of Medical Ethics at New York University's Langone Medical Center and co-founder of the NYU Sports and Society Program, told the newspaper.

"It makes you think, are the physicians looking out for the health of the players, or are they just trying to keep them on the field?" Caplan added.

NFL spokesman Brian McCarthy told the Post that the allegations contained in the court filing "are meritless, and the league and its clubs will continue to vigorously defend these claims."

"The NFL clubs and their medical staffs are all in compliance with the Controlled Substances Act," McCarthy said in an email. "... The NFL clubs and their medical staffs continue to put the health and safety of our players first, providing all NFL players with the highest quality medical care. Any claim or suggestion to the contrary is simply wrong."

The NFL declined to make its medical advisers available to comment to the Post.

Information from The Associated Press contributed to this report.