USADA announced Thursday that a three-member panel of the American Arbitration Association North American Court of Arbitration for Sport handed Bobby Lea a 16-month suspension for failing an anti-doping test at track national championships earlier this summer.

Lea, 32, a two-time Olympian on the track, was found to have noroxycodone, a metabolite of oxycodone, in a sample he provided on August 8 at nationals in Carson, California. Lea won the points race, which was held on the same day that he provided the anti-doping sample. Oxycodone is an opiate, commonly known as OxyContin, a brand-name painkiller. It is classified as an S7 narcotic by WADA, the same class as drugs like heroin and morphine, and is banned in competition but not out.

Lea published an open letter to the sport on his website Thursday evening, explaining that he took the prescription painkiller Percocet (oxycodon is the active ingredient) without realizing that it was banned in competition.

“Because it was late at night, and I was trying to sleep, I failed to check my prescribed medication against the prohibited list, an action I have correctly executed hundreds of times over the years,” Lea said. “Had I done that I would have seen that Percocet is not banned when used out of competition, but is banned in-competition. Had I done that simple check, the same simple check I’ve done in pharmacies all over the world, I would have reached for another beer or two and I would not find myself here today.

“I live with my mistake and I accept full responsibility for it. To my family, friends, coach, fans, sponsors, and the sport that I love: I am deeply sorry.”

The two-time Olympian will appeal the decision to the Court of Arbitration for Sport (CAS). “I want to end my career on the track and not in a lawyer’s conference room,” he said.

Lea did leave open the possibility that he has raced his last race, and that the ban could mark the end of his career. “Now that I’ve lost the ability to write my own ending, I’m left to answer some very hard questions,” he said. “When I look back at my career, how do I feel about what I’ve done knowing that I may have raced my last race?”

USA Cycling CEO Derek Bouchard-Hall released a statement as well. “We were very saddened and disappointed to learn that Bobby Lea tested positive for the narcotic noroxycodone, a metabolite of oxycodone, at the 2015 Track National Championships in August,” he said. “It is not acceptable for an elite athlete to compete with unauthorized prohibited substances in his or her system, and we support USADA’s findings and the sanctions imposed. This case demonstrates the effectiveness of USADA’s testing and adjudication process, and that it is absolutely essential for athletes to be vigilant in competing according to anti-doping regulations.”