Ramirez, in a statement released by the Major League Baseball Players Association, attributed the suspension to his use of a doctor-prescribed medication and waived his right to challenge the discipline.
"Recently I saw a physician for a personal health issue. He gave me a medication, not a steroid, which he thought was OK to give me. Unfortunately, the medication was banned under our drug policy. Under the policy that mistake is now my responsibility. I have been advised not to say anything more for now. I do want to say one other thing; I've taken and passed about 15 drug tests over the past five seasons.
"I want to apologize to Mr. McCourt, Mrs. McCourt, Mr. Torre, my teammates, the Dodger organization, and to the Dodger fans. LA is a special place to me and I know everybody is disappointed. So am I. I'm sorry about this whole situation."
The Los Angeles Times reported that Ramirez tested positive during Spring Training for "a banned performance-enhancing substance that is not technically an anabolic steroid," said a source not authorized to speak publicly about the issue.
The New York Times, citing people in baseball briefed on the matter, reported that urine samples provided by Ramirez showed traces of substances that raised concerns among baseball officials, but it was unclear if it was enough to suspend him. The officials investigated further, according to the New York Times, and found evidence in Ramirez's medical files that he was using human chorionic gonadotropin (HCG), a fertility drug for women that has been known to be used by athletes to generate the body's production of testosterone after steroid use.
According to USA Today, which cited a baseball official, Ramirez was notified in April that he violated the league's policy, and he initially appealed the ruling. But following talks involving MLB and union lawyers Wednesday in Los Angeles, the appeal was dropped late Wednesday, the paper reported.
Ramirez, who turns 37 on May 30, began the suspension with Thursday night's Dodgers-Nationals game. In their first game without Ramirez, the Dodgers lost, 11-9.
Ramirez would be eligible to return around July 3, depending on postponements.
"We share the disappointment felt by our fans, our players, and every member of our organization," Dodgers CEO Jamie McCourt said in a statement. "We support the policies of Major League Baseball, and we will welcome Manny back upon his return."
In a Dodger Stadium news conference during batting practice, manager Joe Torre said the news "caught us by surprise." He said Ramirez's absence would be an immediate "distraction" and leave "a void" in the clubhouse and on the field, but he was also confident the club would remain focused on the task of winning games.
Torre said rather than pointing fingers of blame, players and management need to fix the problems to "regain the trust of fans."
Torre said he spoke with Ramirez by phone twice on Thursday and that the outfielder is "devastated."
General manager Ned Colletti said he felt "sick" and "saddened" when the news was delivered to him and Torre by club chairman Frank McCourt around 12:30 a.m. Thursday.
Reaction around baseball ranged from accusatory to skeptical to even indifferent.
"You see that there's no favorites being played," San Diego pitching ace Jake Peavy said. "That shows you that baseball is serious about what they're saying and doing. I'm happy that we're heading in the right direction."
Giants manager Bruce Bochy concurred with that sentiment, saying the suspension of Ramirez is "a credit to our system."
Colletti said the club has not discussed whether the $7.7 million in salary that Ramirez forfeits of the $25 million he was due this season would be redirected to acquire and pay for other players this year. All suspensions are without pay.
Chief operating officer and president Dennis Mannion said that "Mannywood," the seats by the left-field foul pole rechristened in honor of Ramirez, would be "discontinued for the time being until it's appropriate to bring it back." Instead, the area will be rebranded in honor of the new ZIP code 90090 awarded to Dodgertown.
Ramirez -- a 12-time All-Star who immediately became the face of the Dodgers franchise upon his acquisition last summer -- is the biggest name player to be issued a 50-game suspension under MLB's more stringent drug policy that was adopted in 2006.
According to the drug policy, a player receives a 50-game suspension for a first positive drug test, a 100-game suspension for a second positive test and a lifetime ban for a third positive test.
Ramirez has been a key component in leading the Dodgers to the best record in baseball this year. In 27 games, he is batting .348 with six home runs and 20 RBIs. He is among league leaders in slugging and on-base percentage and has become the biggest drawing card the Dodgers have had since Fernando Valenzuela.
On Wednesday night, Ramirez went 1-for-3 with a two-run double as the Dodgers set a modern-day record with their 13th consecutive home win to open a season.
"[H]im being out 50 games is huge for the Dodgers lineup," said Rockies shortstop Troy Tulowitzki. "It takes the best player in the division out for 50 games. That gives us a little window of opportunity, so hopefully we can take advantage of it."
Juan Pierre is the immediate replacement for Ramirez in left field, while the Dodgers promoted rookie Xavier Paul from Triple-A Albuquerque to replace Ramirez on the active roster.
Ken Gurnick is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.