While the drug Methadone only makes up two percent of painkiller prescriptions, it is responsible for a third of painkiller overdose deaths.
The new report from the Centers for Disease Control and Prevention analyzed national drug data from 1999 to 2010. During that time, four out of every ten deaths from a painkiller involved Methadone. That's two times higher than any other pain reliever.
Methadone was originally used to help heroin addicts, but has been increasingly used as a painkiller. The drug builds up in the body over time and can disrupt breathing and heart rhythm.
Researchers found six times as many people died from Methadone overdoses in 2009 compared to ten years earlier.
Many general practitioners, who don't have experience prescribing complex drugs like Methadone, are writing prescriptions for the drug. Experts say Methadone should not be a first choice pain reliever.