YOUR HEALTH:Drugs found in the singer's body suggest he may have been addicted to a number of prescription drugs over a period of time, the combination of which ultimately proved fatal, writes Dr MUIRIS HOUSTON
WITH POP STAR Michael Jackson’s death ruled a homicide from drug overdose last week, the spotlight is now on the drugs found in his system and the actions of his personal physician, Dr Conrad Murray.
The Los Angeles County Coroner said in his ruling that the powerful anaesthetic propofol, dubbed “milk of amnesia” by some doctors, as well as the sedative lorazepam were the primary drugs responsible for Jackson’s sudden death on June 25th at the age of 50.
However, other medication found in the singer’s body were midazolam, diazepam, lignocaine and ephedrine, suggesting he may have been addicted to a number of prescription drugs over a period of time.
Court document filed in Texas state Dr Murray told investigators that in the six weeks before death, he administered propofol intravenously to Jackson at night to help him sleep. On June 25th, Dr Murray again gave him propofol, briefly left the bedroom of the singer’s home and returned to find him unconscious.
Dr Murray has denied any responsibility for Jackson’s death.
The use of propofol outside an operating theatre, emergency department or intensive care unit is highly unusual. Administering it in a person’s home is downright suspicious. Without using a blood pressure and heart rate monitor, along with devices to check the level of oxygen saturation in the blood as well as a person’s breathing, it is difficult to see how any doctor could justify its use outside the hospital setting.
Propofol’s benefits have made it one of the most widely used anaesthetic agents (see panel). It wears off quickly, leaves no grogginess and doesn’t cause nausea.
A white liquid, which explains the reference to “milk of amnesia”, propofol can be extremely dangerous if not constantly monitored because it can slow breathing and fatally lower blood pressure. Its effects are compounded by other drugs in a person’s system.
Unfortunately for Jackson, he had quite a cocktail of drugs in his body at the time of death. Midazolam is an anti-anxiety and sedative medication, used in palliative care and also for certain dental procedures.
Diazepam (Valium) is a commonly prescribed benzodiazepine useful in the short-term treatment of anxiety and insomnia; however, it is also a commonly used drug of abuse. Lignocaine is a local anaesthetic used to relieve skin itching as well as pain, while ephedrine is both a stimulant and decongestant. Lorazepam, specifically mentioned as a probable cause of death by the coroner, is also a benzodiazepine.
In terms of drug interactions, giving a patient two different benzodiazepine drugs creates an additive effect which, depending on the dosage, could lead to depression of the brain’s respiratory centre and the possibility of respiratory arrest.
Midazolam and propofol could also interact to produce unexpected blood pressure changes, as well as other side effects. A number of studies have found this interaction is more than simply additive, thereby increasing the intensity of sedation by an even greater degree.
Propofol and lignocaine interact to produce a greater hypnotic effect than that found when propofol is used alone.
The coroner’s specific reference to both lorazepam and propofol suggests high levels of both drugs were found in Jackson’s system when post mortem toxicology results were completed. Depending on the levels found, either drug could, on its own or as part of an interaction, have caused the singer’s cardiac arrest.
How could Dr Murray or other doctors involved in Jackson’s medical care be part of what appears on the surface to be reckless prescribing? In the first instance, the physicians may not have been aware of other medication the star was taking unless he volunteered the information to them. But as a recently hired personal physician, Dr Murray would be expected to be up to speed on his patient’s past medical history as well as current medication.
But in prescribing propofol without monitoring, the doctor has at least opened himself to the allegation that he was prescribing well outside normal practice.
He would also have had to consider the possibility that Jackson had a number of drug addictions and the implications of this for the continuing administration of these drugs.
Significantly, however, it has been reported that Dr Murray did not prescribe the propofol he administered, and that Jackson had another source for the anaesthetic.
An important consideration also is that despite the considerable involvement of regulatory authorities in approving drugs and deciding on limitations as to their use, an individual doctor has the right to prescribe any drug “off label”.
This means he or she can prescribe medication for children which has been approved only for adults or he or she can decide to use a drug licensed for epilepsy for pain relief. The doctor has the final say in his prescribing; however, in straying outside both regulators and manufacturers’ guidelines he or she may be asked, in the event of problems, for evidence to back up his decision.
Hollywood and the music industry have always attracted a small number of “high-end” personal doctors who offer personal care to individuals willing to pay high fees. It is up to the California Medical Board, the local medical licensing body, to monitor these physicians and their sometimes dubious practices.
Propofol: the ‘milk of amnesia’
Propofol has been used as an anaesthetic since 1986. It is especially popular as a sedating agent during invasive procedures such as colonoscopy, which involves the insertion of a flexible tube containing a fibre optic camera into the large bowel.
Propofol is a powerful anaesthetic; one of its attractions is its ability to induce amnesia as well as drowsiness during unpleasant but relatively quick medical procedures. It is not available in tablet form and must be given intravenously by someone trained in its use.
It is a fast-acting drug, the effects of which wear off within minutes.
There is no specific antidote to propofol. It was never designed to be used as a sleeping agent and its use outside a hospital or clinic setting is questionable.
Unfortunately, it has become a drug of abuse. Although physical dependency is rare, psychological dependency occurs because of associated feelings of euphoria, relief of stress, pleasant dreams and an ability to induce sexual disinhibition when the recipient wakes up.
Just under 40 cases of dependency on the anaesthetic agent have been reported in the medical literature. This represents only a fraction of cases, many of which go undetected because of the fleeting nature of the drug’s effects.