Volquez is the first player suspended under Major League Baseball's drug program sincelast May.
Volquez's suspension will go into effect Wednesday. The 26-year-old right-hander was already out of action he's recovering from reconstructive surgery on his elbow and was expected to rejoin the Reds around midseason.
An All-Star in 2008 when he went 17-6 with a 3.21 ERA for the Reds, Volquez was 4-2 with a 4.35 ERA last season before feeling pain in his arm in June. He twice went on the disabled list, the first time with back spasms and then with the elbow injury that finished his season.
"The Reds fully support Major League Baseball's drug policy and its penalties. The organization does not condone in any way the use of drugs not sanctioned by MLB's medical staff," the team said in a statement before Tuesday night's game against the Dodgers.
MLB's labor contract does not allow it to release which drug caused the positive test. A list of drugs that trigger positives is released after each season, without identifying which player used it.
Ramirez was suspended after turning over to MLB a prescription for a banned female fertility drug.
Volquez was the first player suspended for a positive test under the big league program since San Francisco pitcher Kelvin Pichardo on March 23, 2009.
The only other players suspended under the major league program last year were Yankees pitcher Sergio Mitre and Philadelphia pitcher J.C. Romero, both in January 2009.
There have been 16 suspensions this year under the minor league drug program.
Volquez made his major league debut with Texas in 2005. He was traded in December 2007 to the Reds for outfielder Josh Hamilton. Both players were at the 2008 All-Star game at Yankee Stadium.