Smart drugs may not be so smart after all.

A new federal government study steps up concerns that Cephalon Inc.'s top-selling drug, Provigil, is addictive.

The research arrives amid reports that college students and some professionals increasingly pop Provigil, Adderal and Ritalin to improve focus and stay awake. Many people now call these pills "brain boosters" or "smart drugs."

The findings, published yesterday in the Journal of the American Medical Association, found that taking Provigil caused changes in the pleasure centers of the brains of 10 men.

The changes resembled those caused by other addictive drugs, such as amphetamines, said Nora Volkow, director of the National Institute on Drug Abuse, who led the study with a Brookhaven National Laboratory scientist.

Cephalon is based in Frazer.

A recent article in the journal Nature said people without medical problems should be able to use these drugs to work harder and longer.

"The Nature article was cavalier, equating it to dangers of drinking coffee, and that was incorrect," she said. "The implication that these drugs are safe, I think, is very misleading."

Provigil is approved to treat excessive drowsiness associated with narcolepsy, obstructive sleep apnea, and shift-work sleep disorder.

University of Pennsylvania brain scientist Martha Farah co-authored the Nature paper. Yesterday, she told the Associated Press that the new study "goes to show that we need a little caution and a little humility when we're messing around with our brain chemistry."

She added that "even now, after all the years that [Provigil] has been on the market, we are still learning things about it that are relevant to its safety."

The Provigil label has included information about the risk of abuse and addiction since the U.S. Food and Drug Administration approved the drug in 1998, Cephalon's chief scientific officer Jeffry Vaught said. He said the company agreed with Volkow that doctors should not prescribe Provigil to healthy people.

Provigil's U.S. sales totaled $943 million last year, according to data provider IMS Health. Analysts have estimated that 80 percent of Provigil prescriptions are for "off-label" treatment of sleepiness and fatigue from illnesses such as depression, Parkinson's disease and multiple sclerosis.

The company is developing a longer-acting version of the drug, called Nuvigil. Yesterday, Cephalon shares jumped 9.3 percent, to close at $69.06 each, after the company reported that Nuvigil met key study goals in a Phase II clinical trial involving adults with bipolar disorder.

Volkow and her group studied 10 men 23 to 46 years old. They received either a dummy pill or modafinil - the generic name for Provigil. PET scans showed higher levels of dopamine among those who took modafinil.

Modafinil also increased dopamine in the nucleus accumbens, a part of the brain believed to be involved with addiction.

Volkow said her research was the first evidence that Provigil affects dopamine transporters in human brains. Although the study was small, Volkow said the clear correlation between Provigil and dopamine levels in the scans was good evidence.

Earlier research had showed the same results in mice and monkeys.

In a September agreement with the Philadelphia office of the U.S. Attorney, Cephalon said it would pay $425 million to settle criminal and civil charges that it illegally marketed three of its drugs, including Provigil, for so-called off-label uses.

Doctors can prescribe a drug for any use, but drug companies can market them only for uses approved by the U.S. Food and Drug Administration. Marketing them for other purposes is known as "off-label."

Contact staff writer Miriam Hill at 215-854-5520 or