Propofol is a powerful sedative designed to be used only in the operating room.

Why Michael Jackson was using it as a sleep aid may never be known. What is known, however, is that it killed him, according to findings released by the Los Angeles County Coroner's office on Friday.

In a statement, the coroner said that propofol and the sedative lorazepam were the primary drugs responsible for Jackson's death. Other drugs detected in his system were midazolam, diazepam, lidocaine and ephedrine.

"Using this drug (propofol) for insomnia is sort of like using a shotgun to kill an ant," Dr. Howard Nearman, department chairman of anesthesia at University Hospitals Case Medical Center in Ohio, told FOXNews.com. "How someone could get a hold of this medication — and use it for the purpose that he allegedly used it for — is just incredible."

Propofol, sold under the brand name Diprivan, which is given intravenously, is used for inducing general anesthesia in the operating room or for heavy sedation of patients who are intubated in the intensive care unit, Nearman said.

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"It should not be used out of an ICU or an operating room setting," Nearman said. "Here at University Hospitals Case Medical Center … Diprivan can only be used by anesthesiologists or intensivists ... and these people, who by virtues of training and experience, can handle this drug and manage any adverse side effect should they arise."

It doesn't take a large dose of propofol to cause respiratory depression, which basically means a person will stop breathing, Nearman said, calling it a "slippery slope."

"Once the breathing is slowed down or the blood pressure drops, eventually the heart won't be able to sustain itself," he said.

Nearman said it's imperative that propofol be used only in a controlled setting where doctors can monitor the heart rate, blood pressure and breathing, and where if anything goes wrong, there is equipment in place to resuscitate a patient.

Jackson's personal physician, Dr. Conrad Murray, was with him at the time of his death and sources say he may be charged with manslaughter in connection with Jackson's death.