But taken the wrong way, methadone can be deadly. It has not yet been determined what drugs — if any — were in Anna Nicole Smith's body when she died, but in her Bahamas refrigerator, next to the SlimFast, there was methadone, according to authorities.
It's unclear whether Smith ever used it, but her son Daniel apparently did. According to a medical examiner hired by the family, a combination of methadone and antidepressants killed him. Experts say he's one of a growing number of young people who've lost their lives to the drug.
"Methadone may be the most underrated problem in drug abuse in the country today," Kay Sanford, a methadone expert at the North Carolina Department of Health and Human Services, told The Early Show national correspondent Tracy Smith.
A recent report found that the number of methadone-related deaths the United States increased by 390 percent between 1999 and 2004. Experts say most kids get the drug from home, so parents need to lock their medicine cabinets.
Methadone stays in the system for days, so any drug taken after it can cause a lethal reaction. And often, teens have no idea what they're taking until it's too late.
"With methadone there are no warning signs," Sanford said. "A person who takes too much methadone simply gets very tired, falls asleep and doesn't wake up."
In Florida — where deaths from methadone have skyrocketed — undercover agents from the Palm Beach Sheriff's Department showed Tracy Smith just how easy it was to get the drug.
"Today we're going to go down to lake worth and attempt to buy some methadone from a lady I've been talking to for the last few weeks," a police officer told Tracy Smith.
The officer told Smith that he believed the dealer he was after would sell to anyone, possibly even a child. Smith and the police officers took positions outside the suspect's home in broad daylight. They hid in the car while an agent went to the door to buy methadone. He rang a cowbell which summoned the woman who would supply him.
Right on schedule, the suspect showed up, looking more like she was on her way to a bingo game than a drug deal. After checking out the street a few times, she approached the agent's vehicle.
She insisted on doing business away from her house, and drove off with the officer. The transaction was brief. A police surveillance tape showed her handing something to the agent, and a few seconds later she was on her way.
She sold the agent methadone pills of 40 milligrams each. A pill costs $20.
For a long time, methadone was considered reasonably safe, as long as people take the proper amount. A 40 milligram methadone pill is divided into quarters and a person should probably only take one of those portions. But children buying it recreationally do not know what amount is safe and might take the entire pill. The result could be fatal.
Some school programs such as "Nope" warn teens about methadone, but they're still not common, even as methadone deaths become more and more common. No matter what killed Anna Nicole Smith and her son — all the attention brought to methadone may be the strongest lesson of all.
"This is a message to everyone," Sanford said. "Even though we have a tendency to focus on our celebrities, most of the people who die from drug overdoses are people just like you and me."