Eli Lilly and Co. (LLY) Thursday said it will add strong warnings to its label for Strattera (search), used to treat attention-deficit/hyperactivity disorder, including the risk of suicidal thoughts among children and adolescents.

Strattera will now carry a "black box" warning (search), the strongest required by U.S. regulators. Such warnings typically hurt sales of products by raising concern among doctors and patients about the safety of a drug.

The Indianapolis drugmaker said a review of clinical trials data identified a small but statistically significant increased risk of suicidal thoughts among Strattera-treated children and adolescents.

Five cases of suicidal thoughts were seen among 1,357 young patients, compared with no cases among 851 patients taking placebos during trials.

"While suicidal thinking was uncommon in patients on the medication during clinical trials, it is important for parents to be aware it can occur, and to discuss any unusual symptoms with a physician," the company said in a release.

There were no suicides among children, adolescents or adults taking the medication during the trials. But there was one suicide attempt among the 1,357 children and adolescents studied, the company said.

The new label warning comes after the Food and Drug Administration (search) asked Lilly to submit an analysis of safety data from its clinical trials.

The company said it is working with the FDA to complete the language on the label. It also is working with regulators outside the United States.

Attention deficit disorder affects 3 percent to 7 percent of school-age children, Lilly said. Symptoms include inappropriate attention and concentration, as well as hyperactivity.

Lilly stood by its sales and earnings outlook for the year, saying it expects full-year earnings per share of $1.90 to $1.96.

Shares of Lilly rose 12 cents to $53.59 on the New York Stock Exchange, amid a slight decline for the drug sector.