It's confirmed, MJ died of an overdose

The leaked toxicology report of Michael Jackson claims that the pop star had lethal levels of potent painkillers and drugs in his body at the time of his death, triggering suspicion that it may be a case of homicide.

Jackson was on a diet of deadly cocktail potent enough to have killed a normal person instantly but his body had developed a tolerance due to the longtime use of huge doses, the British newspaper Sun claimed quoting the findings of his preliminary toxicology reports

High levels of Demerol found in the leaked toxicology report submitted to the Los Angeles county coroner's office, the paper said.

Demerol drug (commonly known as Pethidine (INN) or meperidine (USAN), Demerol is indicated for the treatment of moderate to severe pain, and is delivered as its hydrochloride salt in tablets, as a syrup, or by intramuscular or intravenous injection. For much of the 20th century, Demerol was the opioid of choice for many physicians; in 1983 60% of doctors prescribed it for acute pain and 22% for chronic severe pain

Compared to morphine, Demerol was supposed to be safer and carry less risk of addiction, and to be superior in treating the pain associated with biliary spasm or renal colic due to its putative antispasmodic effects. In fact, Demerol is no more effective than morphine at treating biliary or renal pain, and its low potency, short duration of action, and unique toxicity (i.e., seizures, delirium, other neuropsychological effects) relative to other available opioid analgesics have seen it fall out of favor in recent years for all but a very few, very specific indications. Several countries, including Australia, have put strict limits on its use. Nevertheless, some physicians continue to use it as a first line strong opioid.

Effects of Demerol

Demerol is quickly hydrolysed in the liver to pethidinic acid and is also demethylated to norpethidine, which has half the analgesic activity of Demerol but a longer elimination half-life (8-12 hours); accumulating with regular administration, or in renal failure. Norpethidine is toxic and has convulsant and hallucinogenic effects. The toxic effects mediated by the metabolites cannot be countered with opioid receptor antagonists such as naloxone or naltrexone and are probably primarily due to norpethidine's anticholinergic activity probably due to its structural similarity to atropine though its pharmacology has not been thoroughly explored. The neurotoxicity of Demerol's metabolites is a unique feature of Demerol compared to other opioids. Demerol's metabolites are further conjugated with glucuronic acid and excreted into the urine.


Notable individuals
Well-known people who have been involved in hazardous use[nb 1] or harmful use[nb 2] of Demerol, or who have exhibited dependence[nb 3] on the drug, include:

• David Kennedy, son of Robert F. Kennedy. The cause of his death in 1984 was ruled a "multiple ingestion" of cocaine, Demerol and Mellaril
• Tammy Wynette, singer. Wynette's daughter Jackie Daly alleged in a 2000 book that Wynette had been "hopelessly addicted" to Demerol, Dilaudid, Versed, and other painkillers prior to her death in 1998.
• Michael Jackson, pop singer. Jackson's use of painkillers has been linked to the accidental burning of his scalp on set while filming a Pepsi commercial in 1984. He was treated for painkiller addiction at a rehabilitation clinic in 1993 and later famously referred to Demerol specifically in his track Morphine from the History album, released in 1995. Demerol was among several painkillers found in Jacksons rental house after his death in July of 2009.
• Harold Shipman, "the killer doctor", was also addicted to Demerol.

References
Demerol RxList. Retrieved 19 Jun. 2006.
Babor T, et al., compilers (1994). Lexicon of alcohol and drug terms. Geneva: World Health Organization. ISBN 9241544686. http://whqlibdoc.who.int/publications/9241544686.pdf.