BOSTON — The winner of the CBS reality show "Big Brother 9" pleaded guilty Monday to a drug charge and for failing to file a tax return for the year he won the show's $500,000 prize.

Adam Jasinski, of Delray Beach, Fla., was arrested outside Boston last October and charged with attempting to sell 2,000 pills of oxycodone, the main active ingredient in OxyContin and other painkillers.

He had originally pleaded not guilty to possession with attempt to distribute oxycodone but changed his plea to guilty during a hearing Monday in U.S. District Court in Boston. He also pleaded guilty to the tax charge, which was added Monday by prosecutors.

Sentencing is not scheduled until Jan. 11, but Jasinski was immediately handcuffed and taken into custody to begin serving his time.

Jasinski, 32, was arrested after showing a government witness two plastic bags filled with oxycodone, police said.

While reciting a summary of the evidence prosecutors would have presented if the case had gone to trial, Assistant U.S. Attorney Linda Ricci said the cooperating witness purchased 2,000 oxycodone pills from Jasinski in February 2009. She said Jasinski agreed to fly to Boston in October 2009 to sell the witness another 2,000 pills.

After the witness picked Jasinski up at Boston's Logan International Airport on Oct. 17, 2009, they drove to North Reading, where Jasinski removed a white sock from his pants, Ricci said. The sock contained two plastic bags filled with blue pills later determined to be oxycodone.

After Jasinski won the $500,000 prize on "Big Brother 9" in April 2008, he failed to file an income tax return and failed to pay taxes owed on the money, Ricci said. The series features contestants who live under constant surveillance and vote once a week to evict each other.

Judge William Young said that under federal sentencing guidelines, Jasinski faces a maximum of 14 years on the drug charge. The tax charge is a misdemeanor that carries a maximum sentence of one year.

It was unclear what sentence prosecutors will recommend. A plea agreement was filed in court but was sealed from public view.

Jasinski's lawyer, Valerie Carter, said she planned to recommend a sentence of house arrest. Carter asked Young to allow Jasinski to remain free on bail, with strict conditions, until he is sentenced, but Young rejected that request.

During questioning from Young before he entered his guilty pleas, Jasinski said he is being treated for bipolar disorder and drug addiction.

"I'm actually seeing results," he said.

Carter said Jasinski spent four months in a drug rehabilitation center in Massachusetts, and since then has been in nonresidential treatment in New Jersey, near his parents. She said he has passed every drug test he's been given since his arrest.

In an affidavit filed in court shortly after his arrest, a Drug Enforcement Administration agent said Jasinski told him he had been using some of his winnings from "Big Brother 9" to buy thousands of oxycodone pills and resell them along the East Coast.

At the time, Carter disputed that, saying Jasinski didn't have any recollection of telling agents he used a portion of his winnings to buy oxycodone.