A nurse close to Michael Jackson said that the pop legend was asking for the powerful drug Diprivan in the days before his death, but some pain specialists say such use of the drug would be highly unusual since it's ordinarily given in a hospital setting due to its health risks.
The drug -- known generically as propofol -- is most often used to sedate patients before a medical procedure, but it is also one that palliative care workers have been known to administer to terminal patients who are in pain or who have weeks or days to live as a form of "palliative sedation."
An injection of the drug requires someone to be present in order to continuously administer it intravenously, said Dr. Howard Nearman, chair of anesthesiology at University Hospitals Case Medical Center in Cleveland.
Nearman added there "absolutely" had to be a second party with Jackson if indeed he was using the drug to remain asleep.
Of course, the questions of whether or not Diprivan was in Jackson's system at the time of his death will only be answered with the release of the pop star's autopsy results. However, Los Angeles registered nurse and nutritionist Cherilyn Lee, who worked for Michael Jackson, has come forward saying the pop star begged her give him the drug in the days before he died.
Diprivan is far from the first drug, however, that has been labeled as a possible contributor to his death on June 25. Those close to the star have said that he may have been taking such drugs as OxyContin and Demerol.
While a lawyer for Dr. Conrad Murray, Jackson's personal physician, said the doctor had not prescribed either of those drugs for the pop icon. He has not commented on Diprivan.
Pain control experts say propofol is not intended as a treatment for insomnia, and it isn't even obtainable via a prescription. Its use could have led to respiratory depression and subsequent cardiac arrest if Michael Jackson indeed used the powerful anesthetic to battle insomnia, emergency physicians say.
"There's a big risk here," Dr. John Dombrowski of the American Board of Anesthesiology told "Good Morning America" on Wednesday, listing respiratory failure and the collapse of the patient's heart rate and blood pressure as possible side effects.
And, Dombrowski said, if Jackson was on other painkillers and prescription drugs, adding Diprivan could have created a lethal combination.
Diprivan Known as 'Milk of Amnesia'
The potency of Diprivan as an anesthetic is widely known; in anesthesiology circles, the drug, a white liquid, is termed "milk of amnesia" by some medical professionals.
"Propofol is an agent that requires very close monitoring and is often limited only to use by anesthesiologists," said Dr. Richard Page, head of cardiology at the University of Washington medical center. "The main issue with this agent is respiratory depression, which in turn could cause cardiac arrest."
"It is a very dangerous drug," said Dr. Brian Olshansky, a cardiologist at the University of Iowa who said he often uses the drug to place patients in deep sedation for certain heart procedures. "It is not for sleep. I cannot imagine anyone would use this outside a very regulated environment such as the availability of emergency respiratory equipment."
One main reason for this, he said, is the speed with which the drug has its effect.
"It rapidly induces unconsciousness and apnea," Olshansky said. "People stop breathing within seconds of being given the drug."
These characteristics of the drug make it an exceedingly unusual choice for abuse, said Dr. Jeff Guy of Vanderbilt University, who said such a situation would represent "a quantum leap in the issue of substance abuse."
But despite the effects and risk profile of the drug, Nearman said that patients who've had the drug describe it as inducing "a very pleasant sleep" that "has the potential to be habit-forming."
Odd Effects Come With Diprivan
And Dr. Bruce Goldberger, chief of forensic pathology at the University of Florida, noted that the drug "also acts as an aphrodisiac in men -- it has been reported that men have very vivid sexual dreams while under propofol anesthesia."
Reports from ABC News' Sarah Netter, Luchina Fisher and Russell Goldman contributed to this report.