Addiction to prescription painkillers — which kill thousands of Americans a year — has become a largely unrecognized epidemic, experts say. In fact, prescription drugs cause most of the more than 26,000 fatal overdoses each year, says Leonard Paulozzi of the Centers for Disease Control and Prevention.

The number of overdose deaths from opioid painkillers — opium-like drugs that include morphine and codeine — more than tripled from 1999 to 2006, to 13,800 deaths that year, according to recently released CDC statistics.

In the past, most overdoses were due to illegal narcotics, such as heroin, with most deaths in big cities. Prescription painkillers have now surpassed heroin and cocaine, however, as the leading cause of fatal overdoses, Paulozzi says.

Experts say it's easy to see why so many Americans are abusing painkillers. As Americans age and carry extra pounds, more are asking for pain relief to cope with joint problems, back pain and other ailments.