Overdoses of methadone prescribed as a pain medication are the biggest reason for a spike in poisoning deaths in the U.S., USA Today reported April 2.

The National Center for Health Statistics released a report showing that poisoning deaths outnumbered deaths caused by firearms for the second straight year in 2005. Accidental poisoning is now the second-leading cause of injury death in the U.S., trailing only automobile crashes.

Death rates from car crashes and firearms have remained relatively steady, but poisoning deaths have been rising, mostly because of narcotic drugs. Methadone overdose deaths alone have risen 500 percent between 1999 and 2005.

"When most people think of poisoning, they think of a kid getting under the sink and drinking Drano," says researcher Lois Fingerhut. "That does happen, but it doesn't cause most of the deaths we're talking about now."

Most of the methadone deaths cited by poison-control experts are related to prescription pills, not the liquid version of the drug given to opiate addicts in methadone clinics.

The report was published in the March 2008 edition of the Centers for Disease Control and Prevention's Health E-Stats.