Vienna, Austria ? Abuse of prescription drugs is about to exceed the use of illicit street narcotics worldwide, and the shift has spawned a lethal new trade in counterfeit painkillers, sedatives and other medicines potent enough to kill, a global watchdog warned Wednesday.

Prescription drug abuse already has outstripped traditional illegal drugs such as heroin, cocaine and Ecstasy in parts of Europe, Africa and South Asia, the U.N.-affiliated International Narcotics Control Board said in its annual report for 2006.

In the United States alone, the abuse of painkillers, stimulants, tranquilizers and other prescription medications has gone beyond “practically all illicit drugs with the exception of cannabis,” with users increasingly turning to them first, the Vienna-based group said.

Unregulated markets in many countries make it easy for traffickers to peddle a wide variety of counterfeit drugs using courier services, the mail and the Internet.

“Gains over the past years in international drug control may be seriously undermined by this ominous development if it remains unchecked,” Narcotics Control Board President Philip O. Emafo said.

Discount medications that seem to be authentic often turn out to be powerful knockoffs concocted from recipes posted on the Web, he added.

“Instead of healing, they can take lives,” Emafo said, characterizing the danger as “real and sizable.”

Up to 50 percent of all drugs taken in developing countries are believed to be counterfeit, the board said, citing estimates from the World Health Organization.

Buprenorphine, an analgesic, is now the main injection drug in most of India, and it is also trafficked and abused in tablet form in France, where the Narcotics Control Board estimates 20-25 percent of the drug sold commercially as Subutex is being diverted to the black market.

The number of Americans abusing prescription drugs nearly doubled from 7.8 million in 1992 to 15.1 million in 2003, the Narcotics Control Board said. Among their prescription drugs of choice: the painkillers oxycodone, sold under the trade name OxyContin, and hydrocodone, sold as Vicodin and used by 7.4 percent of college students in 2005.

Although the number of U.S. high school and college students abusing illicit drugs declined in 2006 for a fourth consecutive year, “the high and increasing level of abuse of prescription drugs by both adolescents and adults is a serious cause for concern,” it said.

Counterfeiters are exploiting intense demand for prescription drugs that can give a “high” comparable to cocaine, heroin or methamphetamine, the watchdog group said.

It singled out Scandinavia, where demand for flunitrazepam – a sedative sold as Rohypnol and widely known as a “date rape drug” – increasingly is being met by unauthorized production, and North America, where widespread abuse of prescription drugs, including the narcotic fentanyl – 80 times as potent as heroin – has been blamed for a spike in deaths.