NEW YORK (CNNMoney.com) - Do ADHD drugs cause heart attacks in children?

Following a temporary suspension of Adderall XR in Canada last year, the Food and Drug Administration wants to find ways to study the long-term heart risks of drugs for Attention Deficit Hyperactivity Disorder.

Although this sort of news can cause parental panic, there's no proof that these drugs cause fatal heart attacks. And Ritalin, the most recognizable name in ADHD treatments, has been FDA-approved and on the market for half a century. The first kids who took Ritalin are now old enough to be concerned about the new Medicare bill. So Ritalin, a Novartis (up $0.44 to $55.60, Research)-produced drug that lost patent protection decades ago, is not a new drug with unseen long-term side effects.

The FDA will be taking a close look at ADHD drugs at an advisory committee on Feb. 9. It is responding to reports of sudden death, heart attack, stroke and hypertension in children and adults taking ADHD drugs, the agency said.

The committee will try to find the best way to test the drugs for cardiovascular risks in long-term use.

Although it won't get specific about ADHD products or drug makers, the agency appears to be talking primarily about Adderall XR, the market leader produced by the British company Shire (Research). The FDA issued an alert in 2005 that a Canadian health care agency had pulled Adderall XR off the market because of reports of sudden unexplained death in children taking the drug. It was returned to shelves six months later.

ADHD is a mental disorder that impairs concentration and the ability to control behavior in four percent of U.S. adults and three percent to seven percent of children, according to the American Psychiatric Association. The three drugs are based on separate compounds: methylphenidate hydrochloride for Ritalin; atomoxetine hydrochloride for Strattera, produced by Eli Lilly & Co (up $0.27 to $56.89, Research).; and Adderall XR is an amphetamine. Sold as a generic by various companies, methylphenidate sales totaled $60 million in 2004, according to the most recent figures from Verispan/Drug Topics. This pales in comparison to revenue from its branded competitors: $552 million in 2005 sales for Lilly's Strattera, and $607 million in 2004 sales for Shire's Adderall XR, in the most recent figures available.

On its label, Adderall XR warns that amphetamine misuse may "cause sudden death and serious cardiovascular adverse events." Since 2005, Strattera has carried an FDA warning label that the drug could increase the risk of suicidal thinking in children and teens, which is the type of warning generally applied to antidepressants. Strattera and Ritalin do not carry warnings of potentially fatal heart problems -- although Ritalin's label urges caution in use with patients with hypertension.

Adderall XR, a longer-acting version of Adderall, was yanked off the Canadian market for six months in 2005 because of reports of 20 sudden deaths and 12 strokes in adults and children using the drug. In February, 2005, the FDA sent out an alert that Health Canada, a government health care agency, had suspended marketing of Adderall XR products "due to concern about reports of sudden unexplained death in children taking Adderall and Adderall XR."

But the FDA alert also said there was "a very small number of cases" and that the agency "cannot conclude that recommended doses of Adderall can cause [sudden unexplained death.]" The FDA did not pull Adderall XR from the market. Health Canada allowed Adderall XR to return to the market in August 2005, with a warning about misuse of the drug and the fact that it should not be used in patients with "structural cardiac abnormalities."

Matt Cabrey, a spokesman for Shire, said there is no proven link between Adderall and sudden deaths in any patients, and that there have been more than 50 million prescriptions for Adderall products since their FDA approval in 1996. Referring to the upcoming FDA meeting, Cabrey said it's "an important process and Shire is supportive of the committee evaluation."

Dr. Andrew Adesman, chief of Developmental and Behavioral Pediatrics at Schneider Children's Hospital in Lake Success, N.Y. and an ADHD expert, believes that Adderall XR did not likely cause the pediatric deaths.

Sudden death from heart attacks does occur in children, but it is rare, and no link to ADHD drugs has been proven.

"Adderall XR is back on the market in Canada, because after review it was not clear that Adderall XR was contributing to these risks," said Adesman. "As rare and horrible as these cases are, there's no clear link to medication. So the issue [for the FDA] is teasing out whether there's a risk specific to medication, or whether this is an expected outcome given the numbers of children treated."

But if the risk of death seems slim or nonexistent, why is the FDA scrutinizing ADHD drugs?

Adesman said the FDA was "put in an awkward light" by the Adderall XR's temporary suspension in Canada last year and "is obligated to make sure it has the information it needs to be sure that the medicines are as safe as they believe they are."

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