"Jen is recovering fully and speedily," spokeswoman Lacey Wickline told Reuters.
Wickline said the medication had been prescribed for Capriati by her doctor but did not elaborate.
The Palm Beach Post reported that an ambulance crew rushed Capriati, 34, from her apartment in a hotel-condominium building in Riviera Beach, Florida, to St. Mary's Medical Center in West Palm Beach early on Sunday.
Her father Stefano Capriati told TMZ on Sunday that she was recovering well.
Capriati, formerly the top-ranked women's tennis player in the world who won 14 career titles, including three Grand Slams, and a gold medal at the 1992 Olympics, has a history of drug problems.
In 1994, at the age of 18, she voluntarily entered a drug and alcohol rehabilitation center two days after her arrest on a misdemeanor charge of marijuana possession.
At the time it was alleged that Capriati used heroin, crack cocaine, alcohol and painkillers during a two-day party at a Coral Gables, Fla., motel.
Tom Wineland, who was arrested at the time with Capriati, told police that she was "whacked out on heroin" when they arrested her. He was also quoted as saying that he and Capriati "smoked crack together in the bathroom. She was also eating painkillers and drinking. That makes you pretty high."
Capriati's attorney, John Ross, cast doubt on Wineland's statements, telling a Ft. Lauderdale television station that the tennis champ "exercised extremely poor judgment in associating with the people that she associated with."
Her father also downplayed the incident, telling the Ft. Lauderdale Sun-Sentinel: "She is a teenager. It's a teenage thing."
Capriati's History of Drug Use
Capriati's legal problems -- she was arrested previously in 1993 for shoplifting a $35 ring -- briefly derailed her tennis career, which began at the prodigious age of 13, when she turned pro. The Chicago Sun-Times once called her "the poster child for burned-out sports prodigies."
In 1996, she staged a comeback that culminated in a No. 1 world ranking and captured three Grand Slam titles during 2001 and 2002.
Capriati played her last professional match in 2004 before undergoing shoulder surgery. By her third shoulder surgery in 2007, she had given up hopes of another comeback at age 30. She admitted to the New York Daily News in 2007 that the prospect of life without tennis left her depressed and suicidal.
"When I stopped playing, that's when all this came crumbling down," she said. "If I don't have [tennis], who am I? What am I? I was just alive because of this. I've had to ask, 'Well, who is Jennifer? What if this is gone now?' I can't live off of this the rest of my life."
Reuters contributed to this report.