Per MLB's joint agreement, the suspension means that Cameron tested positive twice for the banned substance.
"I wasn't trying to gain an edge," Maybin said. "I've been taking this medicine for the past three or four years."
Maybin's suspension stemmed from his attention deficit disorder. He previously had a therapeutic use exemption granted going back to February. A prescription change necessitated paperwork that he was not aware he needed to file.
"For me, the toughest part was feeling I did everything I was supposed to do," Maybin said. "I followed protocol like I was supposed to. My only mistake was not knowing that during a prescription change, when you have a TUE [therapeutic use] exemption, you got to go through the process all over again.
"It was my mistake not knowing that."
Maybin said that Major League has since approved the medicine that he was suspended for. He also said Wednesday he considered filing a grievance on the day he was notified of his impending suspension but was told there was a possibility that losing an appeal could lead to more missed time.
San Diego manager Bud Black was happy to see Maybin on Wednesday and could sense his outfielder was ready to put this behind him and play.
"He went through a lot of anguish over this," Black said.
To make room for Maybin on the 25-man roster, the team optioned infielder Jace Peterson to Triple-A El Paso. The team also designated left-handed reliever Bobby LaFromboise for assignment.
Per the terms of his suspension, Maybin was able to play in five Minor League games leading up to his return. He went 5-for-16 with two RBIs and two strikeouts for El Paso.
At the time of his suspension, Maybin was hitting .247, one point lower than his career average, with one home run and nine RBIs in 62 games.
"I just want to play baseball. I felt I was starting to become a guy putting together good at-bats," said Maybin, who missed the first 25 games of the reason while recovering from a ruptured biceps tendon from Spring Training.
"I'm eager to get out there and feel healthy. The situation was a real bummer. I've missed games with injuries. Missing games like this was a real bummer."
Maybin was not in the starting lineup Wednesday, the second of three games against the Dodgers at Dodger Stadium.
Peterson was in his fourth stint with the Padres this season. He was called up on Aug. 14 this last time and had one hit in three at-bats. Overall, he's hitting .113 in 53 at-bats with the Padres in 2014.
LaFromboise has spent the entire season with El Paso, posting a 4.75 ERA in 58 games. He was added as the team's 26th player for a doubleheader in April in Cleveland but didn't make an appearance.
The Padres now have six healthy outfielders on the roster -- Maybin; Abraham Almonte, who had a career high four hits Tuesday; Jake Goebbert; Rymer Liriano; Seth Smith; and Will Venable.
"We have some flexibility with those guys," Black said. "We'll work through it."