WASHINGTON (CNN) - A Food and Drug Administration advisory committee has recommended that the strongest possible safety labels, or "black box" warnings, be added to medicines used to treat attention deficit hyperactivity disorder, after reports that 25 patient deaths may be linked to their use.

Nineteen of those deaths were children, who often take drugs such as Ritalin, made by Novartis (Research), to control behavior that is restless, impulsive and distracted.

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The drugs, taken by millions of patients, also may increase the risk of cardiovascular problems, according to FDA data.

Some of the medicines are amphetamines that already carry warning labels about possible cardiovascular problems, but they are usually aimed at people with existing heart problems.

The FDA does not have to follow the recommendations of their advisory committees, but usually does.

The black box warnings are meant to highlight special problems and potential side effects. The committee said it feels the increased warnings are warranted, until further studies can be done.

The scientific advisers want to determine whether the drugs pose risks, and how much, according to Dr. David Graham, associate director of the FDA's Office of Drug Safety.

In addition to Ritalin, the drugs that would be relabeled include Strattera, Concerta and Adderall. Adderall is an amphetamine; the other medicines are methylphenidates.

While some parents blame the drugs for their children's deaths, Susannah Budington said they are a godsend for her 12-year-old daughter, Allison, who began taking them six years ago.

"Without medication, really, the ADHD severely impacts her life, her ability to stay focused, her ability to do well in school," Budington told CNN. She said Allison has had no side effects.

U.K.-based Shire Pharmaceuticals, the maker of Adderall XR, which has 25 percent of the market share, said its medicine already carries a warning, and it is committed to working with the FDA to make any needed changes.

-- CNN Medical Correspondent Christy Feig contributed to this report.

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