Calls to poison control centers for U.S. teenagers who have overdosed on attention deficit drugs rose 76 percent over eight years, researchers reported on Monday.

This is nearly the same as the 80 percent rise in prescriptions for such drugs, Dr. Jennifer Setlik and colleagues at Cincinnati Children's Hospital Medical Center reported.

They took data from the American Association of Poison Control Centers for 1998 to 2005 for all cases of ADHD drug misuse involving 13- to 19-year-olds.

In 1988, these call centers only logged about 317 calls, but by 2005 they were getting 581 calls a year, they reported in the journal Pediatrics.

Clearly, we are seeing a rising problem with the abuse of these medications, Setlik said in a statement.

The findings suggest that more teens are abusing and misusing stimulant ADHD medications because they have access to those medications, not because a higher percentage of those treated have turned to abusing their medication.

Millions of people take ADHD drugs including Novartis AG's Ritalin, known generically as methylphenidate, and Shire Plc's Adderall and Vyvanse. Annual U.S. sales totaled about $4.8 billion in 2008, according to data from IMS Health.

Attention deficit hyperactivity disorder is marked by restlessness, impulsiveness, inattention and distractibility that can interfere with a child's ability to pay attention in school and maintain social relationships. Amphetamines or methylphenidate drugs can calm and focus the brain.

Prescriptions of amphetamines rose 133 percent from 1998 to 2003, and abuse of these drugs rose, too, the researchers found. We're seeing a disproportionate rise in the calls related to amphetamines, said Dr. G. Randall Bond, director of the Drug and Poison Information Center at the hospital.

One thing we don't know for sure is whether the increased calls for help are the result of simply more abuse or the escalating severity of consequences.

ADHD affects between 8 percent and 12 percent of children and 4 percent of adults worldwide.

The National Institute on Drug Abuse has been investigating reports suggesting that more than 7 million people in the United States have abused methylphenidate to get high or to improve academic performance.

Medicine