The 28-year-old Pridie is on Triple-A Sacramento's roster, and his suspension will start at the beginning of the season. He signed with the A's this offseason as a Minor League free agent after hitting .231 with four homers and 20 RBIs in 101 games for the Mets in 2011.
Tampa Bay's second-round pick in 2002, Pridie was part of the six-player trade in November 2007 in which Minnesota acquired Delmon Young and Tampa Bay acquired Matt Garza and Jason Bartlett.
The Phoenix native has seen time in the Majors in each of the last four seasons with the Twins and Mets. He batted .186 in 14 Minor League games with Triple-A Buffalo last season.
Minor Leaguers are warned after testing positive for a drug of abuse and then suspended after a second violation. The Commissioner's Office does not disclose the specific substance in these cases. Substances considered "drugs of abuse" by Major League Baseball include cocaine, marijuana, heroin, LSD, ecstasy and other opiates.
The Office of the Commissioner has suspended 21 players this year for violations of the Minor League Drug Prevention and Treatment Program.