According to The Associated Press, Patton told The Baltimore Sun he took an Adderall pill four days before the season finished to try to improve his short-term focus.
Under the Joint Drug agreement, 25 games is the penalty for a second positive amphetamine test. A first positive results in evaluation and further testing.
According to The Sun, Patton tested positive for amphetamine use during Spring Training in 2010, also for Adderall.
"We were disappointed to learn of Troy Patton's suspension," Orioles executive vice president of baseball operations Dan Duquette said Friday. "The Orioles support MLB's policy and its efforts to eliminate performance-enhancing substances from the game."
Patton, on Baltimore's 40-man roster, posted a 3.70 ERA in 56 relief appearances for the Orioles last season. Since joining the Orioles in 2010, Patton has gone 5-1 with a 3.04 ERA in 131 appearances.
"I took one because I was stupid," Patton told The Sun. "It was the end of the season. It was just a stupid mistake."
"I don't have trouble focusing all the time, it just enhances focus in certain situations, and I was just tired, basically. I don't want to list that as an excuse. I know I took a banned substance. It was just a poor lapse in judgment," he said.
According to the AP, MLB allows an exemption for players with attention deficit disorder, but Patton told The Sun he'd never been diagnosed. He said he tried to apply for an exemption in 2012 but was rejected after an examination by doctors.
Duquette said Patton's suspension won't dramatically affect Baltimore's bullpen plans heading into Spring Training. With Brian Matusz ensconced as manager Buck Showalter's primary left-handed specialist, the Orioles have several other left-handed options from which to choose.
Duquette specifically mentioned lefties Zach Britton, T.J. McFarland, Mike Belfiore, Kelvin De La Cruz and Chris Jones as candidates for the second lefty reliever job.
"We have some depth to the left-handed relief," Duquette said. "Brian Matusz of course has been our left-on-left pitcher and he's been very reliable, so we have some other good candidates as the second left-hander in our bullpen for Buck and the staff to take a look at this spring."