The team confirmed early Tuesday evening that Dunbar has been released from the reserve/suspended list. He was suspended Aug. 14 for violation of the league's policy on performance-enhancing drugs.
At the time, Dunbar offered only a short statement saying he was not guilty of taking a performance-enhancing drug but that something else had gone awry to lead to a positive test.
"First and foremost, I just want to say I did not take a performance-enhancing drug," Dunbar said then. "I mistakenly took something that prompted a failed drug test. I want to say that I sincerely apologize to my teammates, the organization, coach [Jeff] Fisher, [Les] Snead (Rams general manager), my family and friends. I am deeply saddened by this but I plan to serve my four-game suspension and get back to playing football as soon as possible."
Dunbar, who started all 16 games for the Rams in 2012, would have been eligible to return to the team's active roster Sept. 27, one day after the team plays at home versus San Francisco in a Thursday night contest.
After the suspension was announced, Dunbar went from working with the first-team defense to getting limited repetitions as a backup. Veteran Will Witherspoon replaced him in the starting lineup.
Dunbar finished second on the team in tackles in 2012 with 115 after signing with the Rams from New Orleans in the offseason. He added 4.5 sacks, 13 tackles for loss and a pair of interceptions.
Scheduled to be an unrestricted free agent in the offseason, Dunbar was scheduled to make $1.3 million in base salary this season, although a quarter of that had already been wiped away by the suspension.