I think the investigation is still going on but as I have read he was taking up to 10 xanax a day.
It appears that Michael Jackson did die of an overdose. The overdose was mainly the result of Propofol, a powerful anesthetic used in surgeries and reportedly given to him to treat insomnia. Other drugs were also found in his system, including the sedatives midazolam and diazepam, the painkiller lidocaine and the stimulant ephedrine. However, his death was ruled a homicide--not accidental or the result of self-administered drugs. Michael Jackson's his personal physician Dr. Conrad Murray was charged with involuntary manslaughter for administering the lethal dose.
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