A former lawyer for Michael Jackson's family has expressed concern about the star's use of pain relief medication. Unconfirmed reports suggest the singer had been taking a daily dose of a demerol.
Demerol is an addictive painkiller
Demerol is a strong painkiller, also known as pethidine.
It is an opioid drug in the same drug class as morphine and is addictive. It can be given by tablets or injection.
It works by mimicking the action of naturally-occurring pain-reducing chemicals found in the brain and spinal cord called endorphins.
The drug is usually prescribed in hospitals after operations, and is used as a painkiller during childbirth in the UK.
In the UK, it is classified as a controlled drug, meaning there are strict controls on its supply to prevent it being obtained illegally.
You get a very quick rush from the drug, but the effects wear off after three to four hours, so an addict might risk taking a toxic amount by taking doses through the day.
If taken for prolonged periods, the body can also build up a tolerance to the effects of the drug, so higher doses may be needed to control pain.
Because the drug is addictive, users run a risk of becoming dependent on it if they take it for too long, and may then develop withdrawal symptoms if medication is stopped too abruptly.
The risk of toxicity can depend on what other medications the person is taking, how long they have been taking it, and underlying health problems.
High doses or long-term use can lead to delirium and seizures. High doses can also slow breathing and ultimately stop breathing. This can lead to cardiac arrest.
Other side effects can include nausea, vomiting, headaches, sweating, dizziness and confusion.
US country music singer Tammy Wynette was allegedly addicted to the drug. She died of heart failure at her home in 1998, aged 55.