"I never had seen him take anything, but ... the aftermath was devastating," Jackson's close friend Uri Geller told Britain's ITV1 this weekend. "I couldn't wake him up one day. I said Michael open your eyes. Are you OK?"
Geller and others close to Jackson had good reason to worry, according to Dr. Omar Manejwala of the William J. Farley Center at Williamsburg Place in Virginia.
Manejwala, an expert on propofol, also known by its trade name Diprivan, said the drug is particularly dangerous compared with other sedatives.
"I would say that people die much quicker from this agent than they would from other agents," he said.
Thayne Flora, a former nurse anesthetist, first tried propofol in the early 1990s looking for relief from chronic headaches and family problems. Soon, she was addicted.
"You know, part of it is wanting to sleep and part of it is wanting to escape from pain, emotional, physical," she said. "And it just makes you go away for a while and you don't have to cope with those things anymore."
Jackson died June 25 of an apparent cardiac arrest, weeks before he was to kick off his 50-concert "This Is It" tour at London's O2 Arena.
Several of Jackson's doctors are now under investigation by the Los Angeles Police Department and the federal Drug Enforcement Administration with the focus narrowing on Dr. Conrad Murray, the doctor who last saw Jackson alive. Investigators want to know whether Murray administered propofol to the entertainer. Murray and his lawyer have refused to answer questions about whether he administered the powerful drug to Jackson.
The coroner's office is also being looked at to determine whether employees leaked or sold information relating to Jackson's death.
Murray has repeatedly denied giving Jackson anything that could have killed him, but a raid on his Houston office last week collected evidence that could be used against the doctor on possible manslaughter charges.
Law enforcement officials close to the investigation have told ABC News that propofol was among the evidence removed from the rented Los Angeles mansion where Jackson died.
Jackson's nurse Cherilyn Lee, whose medical records were also subpeonaed last week, spoke out in the days after the singer's death, saying she refused to give him propofol even as she could hear him pleading on the phone.
Lee said she was especially concerned about Jackson when, in the days before he died, she got a call from someone at the house.
"And I could hear Michael in the background, 'Tell her. Tell her that one side of my body is hot ... and one side of my body is cold,'" she said last month.
Experts say people who abuse propofol run the risk of sudden respiratory arrest.
TMZ reported overnight that paramedics found Jackson with an IV in his arm alongside an empty IV bag and an oxygen tank, and that Murray got in the way as emergency workers tended to Jackson at the scene.
Geller, an author and psychic, said he knew his friend couldn't survive as an addict.
"'Michael,' I shouted, 'You will kill yourself!'" Geller said.