AJ Allmendinger has been reinstated from his indefinite suspension from NASCAR and can return to competition, the sanctioning body announced on Tuesday.
The 30-year-old has successfully completed NASCAR's Substance Abuse Policy Road to Recovery Programme after first being temporarily suspended on July 7.
This followed a positive test for banned substances performed on June 29, which was then confirmed by a further 'B' sample test that led to an indefinite suspension on July 24.
Allmendinger was later released by Penske Racing, with Sam Hornish Jr taking over his seat in the #22 Dodge from July's Daytona race. Joey Logano has since secured the drive for 2013.
"I want to thank everyone for their support. I am grateful for the opportunity to return," said Allmendinger in a statement.
"The Road to Recovery programme was really helpful to me in getting my priorities reset away from the racetrack. And, honestly, that helped find my love of racing again and why I began racing in the first place."
Champ Car race-winner Allmendinger visited the IndyCar season finale at Fontana last weekend, igniting speculation over a potential return to open-wheel racing.
His former boss Roger Penske, who signed him to replace 2004 Sprint Cup champion Kurt Busch this year, told reporters at Fontana that he would consider hiring Allmendinger again.
"He could be an option for us, for sure," Penske said on Saturday.
He added: "Hopefully they'll give him a clean bill of health so he can move on. Obviously, it's a speed bump in his career.
"He's certainly an option for people on the NASCAR side and on the Indy side. He did a great job [in] Champ Car."
Following Allmendinger's suspension, Grand-Am team owner Michael Shank also said he would like to have Allmendinger in one of his cars following their victory together in this year's Daytona 24 Hours.