02/05/2008 at 11:40 PM EST
's death on Jan. 22 was due to an accidental mixture of prescription drugs, New York City's Chief Medical Examiner has concluded.
"Mr. Heath Ledger died as the result of acute intoxication by the combined effects of Oxycodone, Hydrocodone, Diazepam, Temazepam, Alprazolam, and Doxylamine," said an announcement released Wednesday morning by office spokeswoman Ellen Borakove.
"We have concluded that the manner of death is accident, resulting from the abuse of prescription medications," the two-paragraph statement said in its entirety.
Oxycodone is a painkiller, Hydrocodone is also known as Vicodin, Diazepam is commonly called Valium, Temazepam treats anxiety or sleeplessness, Alprazolam is known as Xanax, and Doxylamine is a sedating antihistamine often used as a sleep aid.
Dr. Michael Hunter, a prominent forensic pathologist not involved in the Ledger matter, tells PEOPLE that the combination of the powerful drugs most likely caused "poly-drug intoxication" which led to respiratory arrest. "His breathing probably got slower and slower until it stopped all together," he said.
Hunter also said it is highly unlikely a doctor would have allowed Ledger to take all the different types of drugs in his system (though another doctor, Vatsal Thakkar, a psychiatrist at NYU Medical Center, tells PEOPLE that it could be "sloppy prescribing"). Either way, "This is a dangerous mixture of drugs," said Hunter. "We are seeing more and more people dying of poly-drug intoxication from prescription drugs and it usually a combination of the narcotic-type drugs seen here."
Hunter said it's important to note that the Medical Examiner officially ruled the death an accident, which means they must have ruled out suicide. He also said they officially determined his death was caused by the "abuse" of prescription drugs, which is telling.
"When they use the term abuse it tells us that he used drugs to obtain an intoxicant effect and not for a therapeutic reason. They must have determined through their investigation that the drugs were not for therapeutic use."
The actor, 28, was found dead
in his Manhattan apartment on Jan. 22. Authorities said at the time that they did not suspect foul play but that medication was found near the body. (Six medications
, including anti-anxiety medications and sleeping pills, were found near the body.)
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