On the heels of massive concussion litigation that the NFL is still trying to resolve, the league now faces a new courtroom challenge that takes aim at the way professional football teams distributed drugs to players for the past four decades.

More than 600 players, led by former stars Jim McMahon and Richard Dent, filed a class-action complaint in U.S. District Court in San Francisco on Tuesday alleging the league illegally supplied them with painkillers to conceal injuries and mask pain. The players say addictive drugs were administered without proper prescriptions, in illegal doses, without medical supervision and with little or no explanation of risks and dangers.

“Rather than allowing players the opportunity to rest and heal, the NFL has illegally and unethically substituted pain medications for proper health care to keep the NFL’s tsunami of dollars flowing,” the complaint reads.

The NFL’s lawyers declined to comment on the suit Tuesday afternoon, saying they had yet to read it, a league spokesman said. Last year, NFL Executive Vice President Jeff Pash told The Washington Post: “The whole issue of pain meds is a big, important issue in our society well outside the NFL. It’s something that needs to be addressed on a broad basis, not just in [the] NFL, and it is something our doctors are looking at.”

NFL Commissioner Roger Goodell said at the conclusion of Tuesday’s NFL owners meeting in Atlanta that he had not yet been able to study the details of the lawsuit.

The NFL reached an agreement last year to settle concussion-related litigation with former players for $765 million. A federal judge in Philadelphia rejected the deal, though, asking both sides to review the terms and make certain the funds are sufficient. Six of the eight named plaintiffs in Tuesday’s lawsuit are also involved in concussion-related cases.

“I can’t say for certain that what we’re alleging is more numerous or more widespread than concussions, but common sense tells me that it probably is,” said Steven Silverman, one of two attorneys representing the plaintiffs.

Similar to the concussion litigation, Tuesday’s filing portrays a culture within the NFL in which common medical practices deviate from the norm. It describes a league in which players were given a variety of opioids, non-steroidal anti-inflammatory medicines and anesthetics to prep them for the physical toll awaiting them on the football field. Many players, the suit says, still struggle with addiction or the health trauma associated with excessive drug use during their playing careers.

Drugs aimed at treating pain have long been a part of the NFL. As part of a five-part series examining medicine in the NFL last year, The Post surveyed more than 500 former players and one in four said he felt pressure from team doctors to take medication he was uncomfortable with. Nearly nine in 10 reported playing games while hurt, and an overwhelming number — 68 percent — said they did not feel like they had a choice but to take the field.

In the lawsuit, McMahon says he suffered a broken neck and ankle during his career as an NFL quarterback from 1982 to ’96 and was “pushed back on to the field” with the aid of medications. He became addicted to painkillers, according to the lawsuit, at one time consuming more than 100 Percocet pills in a month.

For many ex-players, drugs were a regular part of game preparation, according to the lawsuit. They allege that trainers would ply them with medication to sleep and distribute different medication the next morning to prepare them for kickoff.

Plaintiff Jeremy Newberry, an NFL offensive lineman from 1999 to 2008, would receive as many as six injections during the course of a game, in addition to pills before and after games, according to the lawsuit. He suffers from renal failure and high blood pressure. Roy Green received “hundreds if not thousands” of injections as an NFL wide receiver from 1979 to ’92, the suit alleges. Now 56 years old, he has suffered three heart attacks and in 2012 had a kidney transplant because of failing kidneys.

The lawsuit alleges that dependency on pain medication outlasts football careers. One plaintiff, J.D. Hill, an NFL wide receiver from 1971 to ’79, says after he retired from football, he “was forced to purchase [drugs] on the streets to deal with his football-related pain” and eventually became homeless.

In addition to seeking unspecified compensatory and punitive damages, the class of ex-players seeks a medical monitoring program and wants the league to pay for treatment.

“The NFL pushes profits; they put their own profits above the players’ health,” said Mel Owens, the other attorney representing the plaintiffs. “You cannot play in this league without medication; it’s too arduous.”

Sally Jenkins contributed to this report.