After a sharp rise, the number and rate of methadone-related overdose deaths have fallen since 2007, the CDC report shows.
Health officials describe the recent trend as closer to a leveling off than a reversal. But they also acknowledged it was a bit of good news in what has been a deteriorating situation.
"There aren't a lot of problems that have gotten so much worse so quickly as prescription-drug overdose has," CDC Director Thomas Frieden said.
Methadone is a powerful drug that can be underestimated. It accounted for just 2 percent of painkiller prescriptions in 2009 but more than 30 percent of overdose deaths, according to the CDC.
The drug mimics the effects of heroin and has been used to wean users off their addiction. Regular doses of methadone can reduce heroin cravings and withdrawal symptoms.
Roughly 15 years ago, doctors started prescribing methadone more often for pain, partly because they were looking for an alternative to OxyContin, a narcotic pain reliever that increasingly was being tied to drug abuse and death. Methadone seemed like a safer alternative, said Len Paulozzi, the CDC study's lead author.
Insurers also encouraged doctors to prescribe methadone because it's cheaper than some other painkillers.
But too much methadone can disrupt breathing, causing death. It also can cause a fatal irregular heartbeat, CDC officials say.
The CDC said the number of methadone-related deaths rose from fewer than 800 in 1999 to more than 5,500 in 2007, before slipping the next two years to 4,900 and 4,700.
What's behind the change? The researchers note that the Food and Drug Administration in 2006 warned doctors to be more careful in prescribing the drug. And in 2008, methadone manufacturers voluntarily limited distribution of the largest doses to only hospitals and to addiction-treatment programs.
Meanwhile, more states started or toughened up programs to monitor prescriptions for painkillers and look for signs of abuse.