St. Pierre, who was in Spring Training camp with Boston, will begin serving his ban immediately upon signing with another Major League organization.
The Quebec City native, who turns 32 next week, signed with the Boston Red Sox as a Minor League free agent on Jan. 17, 2012, and had been assigned to Triple-A Pawtucket on March 23 before being released.
St. Pierre is the 30th player suspended in 2012 for violating the Minor League program.
St. Pierre has spent most of his career in the Tigers system -- he made his Major League debut on Sept. 4, 2010, becoming the oldest Tigers position player to make his big league debut since 1961 (Mike Roarke).
A MiLB.com Organization All-Star and a Path of the Pros subject in 2010, St. Pierre admitted he has previously battled with substance abuse.
"That's when  things got out of hand a little bit and I realized that I needed some help," St. Pierre told Baseball Prospectus in 2010. "I basically just wanted to quit and go on with my life -- the drinking and party thing. I was starting to hurt people who were close to me. That's when I realized that it had to stop. If I don't have anybody -- my family and the people close to me -- if I end up with no friends, what am I going to do? I wouldn't have anybody to help me."
Players are typically issued a warning following a first positive test for a drug of abuse, followed by a suspension for a second offense. Substances considered "drugs of abuse" by Major League Baseball include cocaine, marijuana, heroin, LSD, ecstasy and other opiates. Minor Leaguers who test positive for a performance-enhancing substance are subjected to an immediate 50-game suspension.
St. Pierre appeared in six Major League games with Detroit in 2010 but spent all of last season at Triple-A Toledo, where he batted .207 with four homers and 25 RBIs in 77 games.
The 2005 Eastern League All-Star also spent time with the Brewers and Royals as well as playing for Canada at the 2006 World Baseball Classic.