Reports of prescription drug abuse have dogged Michael Jackson for much of his career, and now a close associate has come forward to talk about the late singer's battle with addiction.
Jackson's former video producer said the pop star, who died Thursday at age 50 from cardiac arrest, had a "20-plus year" addiction to the painkiller Demerol, as well as to a cocktail of other drugs, such as Oxycontin.
Jackson became so addicted that the video producer and other close associates tried to stage an intervention in 2003, but it derailed because of a world tour, said Marc Schaffel, who was named as an unindicted co-conspirator in Jackson's 2005 child molestation trial.
Schaffel's accusations were backed by a senior law enforcement official who told ABC that Jackson was "heavily addicted" to Demerol and received "daily doses" of Oxycontin.
Jackson even wrote and performed a song about the drug Demerol, called "Morphine," released in 1997. Both drugs are opioids.
"Everybody around him knew about it," Schaffel told ABCNews.com. "He didn't advertise it to the world, but anybody in his inner circle knew."
"I was shocked, but I knew it was only a matter of time that something like this would happen," Schaffel said. "I have said before, that if he continued using drugs at this rate, he'd be dead by the time he was 50."
Schaffel won a $3 million suit against Jackson, claiming the star failed to pay him $800,000 for his work on two television specials, and $2.3 million in payments and loans over a number of years.
The Los Angeles police were told that Jackson received a Demerol injection one hour before his death, according to a senior law enforcement official. Paramedics at the Los Angeles hospital where Jackson died Thursday, according to the British tabloid the Sun, said the star's breathing got "slower and slower until it stopped."
Doctors Say Drugs Likely
Medical experts speculated that drug abuse was a likely cause of death, though partial autopsy results will not be available until later today.
"Demerol may be responsible," said Dr. Christopher Gharibo, director of pain medicine at New York University Hospital for Joint Diseases. Demerol is usually administered by nurses, said Gharibo. "If the respiratory arrest occurred immediately after the Demerol injection, there was an overdose situation that either caused a seizure or respiratory depression leading to cardiac arrest."
Dr. Bruce Goldberger, chief of forensic pathology at the University of Florida, said, "Any time you have a 50-year-old man pass away in generally good hearth who's recently had a physical exam, the first thing you think about are drugs."
Primary death from cardiac arrest with this cocktail of drugs is highly unlikely unless Jackson was also using amphetamines or had a history of heart disease, according to Dr. Darin Correll, an anesthesiologist at Brigham and Women's Hospital in Boston.
The 911 audio tapes revealed that a "personal doctor" was present when paramedics were called..
"This whole thing is a little bizarre," said Correll. "You'd think that person would have been able to adequately perform CPR and stop it. If it truly was from opioids, it's easily fixed."
An overdose can be "reversible," he said, by administering mouth-to-mouth rescusitation and then an antidote -- Naloxone.
Schaffel, who produced Jackson's "Private Home Movies" in 2003, said his friend's addiction to Demerol began as early as 1984, when the pop star suffered burns when his hair caught fire filming a Pepsi commercial. He was later was treated at the Betty Ford Clinic.
In 2002, Jackson was ordered to undergo a medical examination after he failed to show up in a California court room in a trial over breach of contract because the pop star said he had a spider bite.
"He had the IV stuff back then," said Schaffel, "It wasn't a spider bite. It was an IV he pulled out his leg. The needle broke off."
Jackson had complained of a series of medical maladies since the beginning of the 2002 civil trial in which he was accused of backing out on a pair of millennium concert performances.
He arrived at the Santa Monica courthouse on crutches and wearing only one shoe, telling reporters that he had awakened to find his left foot too swollen to fit in a shoe.
Michael Jackson's Demerol Use
At the time, Jackson claimed the bite had not come from one of the tarantulas he kept as pets at his Neverland Ranch, but rather a small spider when the compound was being fumigated.
It has been widely reported that in addition to Demerol and Oxycontin, Jackson also abused the anti-anxiety drug Xanax and the anti-depressant Zoloft in the months before his death.
Demerol, a powerful prescription painkiller and opioid, often used in childbirth labor, is highly habit-forming.
A well-known side effect of Demerol and other pain medications is respiratory depression, according to Sanjay Sethi, chief of pulmonary, critical care and sleep medicine at University at Buffalo in New York.
"A large dose, especially if given intravenously, can act on the respiratory center of the brain, reduce respiratory drive, cause cessation of breathing, leading to cardiac arrest because of lack of oxygen," Sethi told ABCNews.com. "Antidotes are available, but they have the best effect only when used prior to cardio-respiratory arrest."
Both rock icon Elvis Presley and movie star Heath Ledger died of combination drug overdoses, the former in 1977 and the latter in 2008.
Lisa Marie Presley, who was briefly married to the pop star, said on her MySpace page that Jackson feared he would die like Elvis.
"At some point he paused, he stared at me very intensely and he stated with an almost calm certainty, 'I am afraid that I am going to end up like him, the way he did,'" wrote Presley.
According to the U.S. Drug Enforcement Administration, more than 8,500 deaths nationwide involved prescription pain relievers in 2005, an increase of 114 percent since 2001.
In addition, nearly one-third of individuals who began abusing drugs in the past year reported their first drug was a prescription drug. About 19 percent of those were opioids.
Jackson's family lawyer, Brian Oxman, compared the star's death to that of Anna Nicole Smith, who died in 2007 of a drug overdose.
"This family has been trying for months and months and months to take care of Michael Jackson," said Oxman. "The people who have surrounded him have been enabling him."
But producer Schaffel said it was a coterie of "pseudo doctors," including a South Florida physician and a New York City anesthesiologist, who provided Jackson with drugs, often prescribed to others.
Demerol Abuse Uncommon
Demerol is as addictive as morphine and levels can store up in the body and cause such serious effects as seizures and tremors. When used with alcohol, other opioids or drugs that induce central nervous system depression, it can be particularly dangerous.
Demerol interacts dangerously with "about a hundred" other drugs, according to Dr. Christopher Cannon, a cardiologist at Brigham and Women's Hospital in Boston.
"Like any narcotic, people build up tolerance to opiates," he told ABCNews.com. "They need higher doses to get the pain effects. But to be on IV Demerol is practically unheard of from someone who hasn't had surgery. It's very unusual."
With Demerol, "there is a whole laundry list of things that are counterindicated, to be avoided or caution is advised," said Cannon.
"Once you start taking additional medications, six, seven or eight at a time, interactions start happening and it's a set up for this -- the feared complication -- that's why we do EKGs on various medications that are known to affect the heart."
Plastic surgery aside, looking over Jackson's physical decline over the past decade, drug use certainly make sense, according to Cannon.
"Emaciation is a classic thing [in drug addiction] and he fits that in his face," said Cannon. "It's very possible that it's part of his physical change and decline. Certainly mentally -- he has been very erratic in his behavior. "
During the 2005 child molestation trial, the judge ordered prosecutors to return hundreds of items that were not deemed "contraband," according to The Associated Press at the time.
Those items included syringes, the drug Demerol and prescriptions for various drugs, mainly antibiotics, that were in different people's names.
Prior to Jackson's arrest and the raid on his Neverland ranch, some of the star's doctors talked about staging an intervention, according to Schaffel.
"We actually didn't do it, but we were talking about it when we were getting ready to leave on a six month trip," he said. "We had spent Christmas and New Year's at Elizabeth Taylor's place in the Swiss Alps and we were headed to do an award show in German and France and South America."
"The misconception is talking about people enabling him," said Schaffel. "About 90 percent of the people had nothing to do with the drug use. His regular doctors didn't give him drugs."
Schaffel said he had last seen Jackson a few years ago, when a British television network approached the producer about running the private home movies.
"When you've got that kind of money, you can get your drugs," he said of Jackson. "We call them Dr. Feel Goods. We tried to intercept and block them, but when you have that kind of money, you can get them on your own."
ABC News' Karin Halperin contributed additional reporting for this story.