Q:What are the drugs that have been mentioned in connection with Jackson's death and how do they work?A:Propofol (Diprovan): A powerful intravenous sedative - not a DEA controlled substance - was found on the premises. It is used by anesthesiologists to put a patient to sleep before general anesthesia and surgery, or alone in a surgical suite for an elective procedure such as a colonoscopy or biopsy. Only small doses are necessary to be effective, and it can easily be misused by an untrained health professional leading to a respiratory arrest.

Narcotics:Demoral, Percocet, Vicodan - there are varied reports of prescriptions for these being found. All can lead a patient to stop breathing or sustain a cardiac arrhythmia and cardiac arrest if overdosed - especially if used in combination. These are controlled substances and prescriptions are subject to DEA review. Misuse can lead to loss of license or criminal prosecution.

Sedatives:A prescription for Xanax was reportedly found. This can also lead to supressed breathing.

Q: What are the questions about substandard care that surrounded Jackson's death? A:Excess prescriptions of narcotics and sedatives. When he stopped breathing, no opiate antagonist (narcan) was given to reverse the effects of narcotics. The doctor in residence did not coordinate the 911 call. CPR was done on the bed without a backboard, rather than on the floor where more force could be administered to the heart. No defibrillator was available, and no mouth-to-mouth breathing was reportedly given.

Q: Why is there a delay in getting the autopsy results? A:The initial autopsy apparently showed no structural damage to the heart to explain his death. There is speculation that prescription drugs contributed to or caused Jackson's sudden death, and initial toxicology reports may soon be ready. More extensive reports take longer because they look at blood and hair to quantify the exact amounts and combinations that could have led to his death. This will include a microscopic examination of the brain itself, which could show the effects of drugs and help determine the exact cause of death.

Dr. Marc Siegel is an internist and associate professor of medicine at the NYU School of Medicine. He is a FOX News medical contributor and writes a health column for the LA Times, where he examines TV and movies for medical accuracy. Dr. Siegel is the author of "False Alarm: The Truth About the Epidemic of Fear"and "Bird Flu: Everything You Need to Know About the Next Pandemic."Read more at www.doctorsiegel.com

Dr. Marc Siegel, a practicing internist, joined FOX News Channel (FNC) as a contributor in 2008..