From ScienceBlogs:

Judging from the press inquiries, expect focus on the Michael Jackson case to be on the anesthetic drug, propofol (Diprivan®).

California nutritionist and registered nurse Ms Cherilyn Lee gave an interview to Campbell Brown on CNN (and this AP exclusive report) describing Michael Jackson's repeated requests of her for the intravenous sedative drug for his insomnia. She wisely rejected his requests, instead providing him with a vitamin and mineral "energy" injection.

However, four days before Jackson's death she reported a frantic phone call from a Jackson staffer to her that led her to believe he had somehow procured the drug or something like it.

Diprivan is the trade name for propofol (PROPE-uh-fawl), a product of AstraZeneca whose healthcare professionals website on the drug is currently closed. Estimated US annual sales of Diprivan are $375-400 million USD. Propofol has a deceptively simple chemical structure and is known chemically as 2,6-diisopropylphenol.

It is a widely-used intravenous anesthetic used primarily for outpatient surgical procedures owing to its very rapid onset of action, sometimes as fast as 30 sec, and rapid recovery.

Propofol has a remarkably good safety record given its widespread use. The average human intravenous dose is 2 to 2.5 mg per kg body weight while the intravenous LD50 (dose that is lethal to 50% of a population) in mice is 50 mg/kg. When used alone, or in combinations with the opioid analgesic fentanyl, it produces a "dissociative analgesia" that is very rarely fatal. Hence, its safety is one of the reasons it is used for outpatient surgery, together with its rapid onset and quick recovery.

While it is a sedative, it has been reported to produce euphoria in some people (the pleasant feelings of well-being most often associated with morphine and other opioids).

The potential risk is from "propofol-related infusion syndrome" - it can produce an elevation in body temperature that is usually not fatal (not "true" malignant hyperthermia as with the rare but fatal side effect of some inhaled anesthetics) but can trigger muscle breakdown called rhabdomyolysis, a rare but devastating side effect that can also occur with statin cholesterol-lowering drugs.

An excellent and timely review of propofol-related infusion syndrome was published in the May issue of Pharmacotherapy by authors from the University of Houston College of Pharmacy and is reprinted at Medscape. Most notable in this review is that while the syndrome is rare, it is fatal in 64% of cases when it does occur.

However, most relevant to the Jackson case is that propofol can cause cardiac tachyarrhythmias (rhythmic disturbances at high heart rate), especially in people predisposed to cardiac problems.