Prescription painkillers may seem a world away from heroin, but experts say that moving between the two is actually quite common.

Prescription drug abuse took off more than a decade ago, partly because the medication came in exact dosages and lacked the stigma of more illicit drugs, according to Theodore Cicero, a psychiatry professor at Washington University in St. Louis.

"These are safe, they're predictable," Cicero said. "It makes the use socially acceptable."

The Centers for Disease Control and Prevention called prescription drug abuse the fastest-growing drug problem in the U.S.

Cicero authored a study in July about the effects of the change in Oxycontin's formula in 2010. Oxycontin was one of the most popular drugs among abusers, but it saw a downslide in use when a new version that was harder to crush and inject or inhale was introduced. Meanwhile, heroin was only getting cheaper and purer.

While 35.6 percent of opioid patients surveyed by Cicero listed Oxycontin as their primary drug in 2009, only 12.1 percent said the same thing when the study concluded in 2012. Cicero compared the effect to pressing on one part of a balloon, only to see the air pop up somewhere else.

"What was not thought about was, 'Where are these drug users going to go?' " he said. "A significant percentage went right to heroin."

The shift out to the suburbs is having other consequences, said Wilson Compton, director of the Division of Epidemiology, Services and Prevention Research at the National Institute on Drug Abuse. Compton noted a significant increase in hepatitis C -- a disease transmitted almost completely through infected needles -- among younger people.

"It's a reflection of this resurgent heroin epidemic," Compton said. "Families and communities need to realize that this can happen almost anywhere." - Matt Connolly