The report by the department's National Drug Intelligence Center identified the main drug threats in the United States for the coming year.
"In some areas, such substitutions among prescription drug abusers have been widespread, creating new challenges for local law enforcement and public health agencies compelled to address a widening local heroin user population," it said.
The study also found rates of pharmaceutical drug abuse, including pain relievers, tranquilizers, stimulants and sedatives, exceeded that of all other drugs, except marijuana.
According to reports from California, Florida, Michigan, Ohio and Wisconsin, some opiate abusers in those states who began using OxyContin have progressed to heroin.
Nearly 79 percent of state and local law enforcement agencies reported high or moderate availability of diverted pharmaceuticals in their area. Demand for the drugs has remained high, with use by an estimated 15,172,000 people.
The report also identified a growing influence of Mexican and Asian criminal groups in drug distribution and easier availability of more potent forms of marijuana and methamphetamine.
"The production of high potency marijuana in Canada and the United States by Asian criminal groups has been a leading contributor to rising marijuana potency throughout the United States," the report said.
It said Mexican drug traffickers have recently begun producing more potent marijuana and have expanded their control over methamphetamine distribution.
The report also said cocaine availability and use in the United States has not significantly changed despite record interdictions and seizures. Southern Texas remains the leading area of entry for cocaine smuggled into the United States.
source - Reuters