Twins prospect Anthony Swarzak had been suspended 50 games for violating the minor league drug prevention and treatment program.
This isn't a PED suspension. Instead, he apparently was caught using marijuana or something worse. Swarzak is the Twins' top pitching prospect below Triple-A. He struggled mightily to begin this season.

he commissioner's office announced this afternoon that Twins righthander Anthony Swarzak, 21, had been suspended 50 games for testing positive for "a drug of abuse," in violation of the minor league drug prevention and treatment program.

Drugs of abuse as defined in baseball rules do not include steroids or other performance-enhancing substances, but instead amphetamines and illegal drugs such as cocaine or marijuana.

Swarzak, a second-round pick out of a Florida high school in 2004, was ranked as the Twins' No. 5 prospect in the offseason after going 11-7, 3.27 at high Class A Fort Myers in 2006. He had opened the season 0-2, 11.12 at Double-A New Britain, striking out seven and walking five in 5 2/3 innings.

http://www.baseballamerica.com/blog/prospects/?p=186