Accidental overdoses and side effects from attention deficit drugs likely send thousands of children and adults to emergency rooms, according to the first national estimates of the problem.

Scientists at the U.S. Centers for Disease Control and Prevention estimated problems with the stimulant drugs drive nearly 3,100 people to ERs each year. Nearly two-thirds — overdoses and accidental use — could be prevented by parents locking the pills away, the researchers say.

Other patients had side effects, including potential cardiac problems such as chest pain, stroke, high blood pressure and fast heart rate.

Concerns over those effects have led some doctors to urge the Food and Drug Administration to require a "black box," its most serious warning, on package inserts for drugs such as Ritalin, Concerta and Adderall. Yet even doctors advising the FDA don't agree on whether that's warranted.

The issue was discussed in a series of letters in the New England Journal of Medicine, including some from doctors worried about the dangers of not treating attention deficit hyperactivity disorder.

"The numbers (of side effects) are puny compared to the numbers of stimulant prescriptions per year," said Dr. Tolga Taneli, a child and adolescent psychiatrist at University of Medicine and Dentistry of New Jersey in Newark. "I'm not alarmed."

Other health experts assert their positions that Ritalin and other ADHD drugs are completely unnecessary to treat ADHD and that there are healthier and safer alternatives such as educational, behavioral, nutritional and herbal therapies which are touted as far more effective with little or no risk at all.

An estimated 3.3 million Americans who are 19 or younger and nearly 1.5 million ages 20 and older are taking ADHD medicines. Ritalin is made by Novartis Pharmaceuticals Corp. of East Hanover, N.J.; Concerta by Johnson & Johnson of New Brunswick, N.J., and Adderall by Shire US Inc. of Newport, Ky.

Twenty-five deaths linked to ADHD drugs, 19 involving children, were reported to FDA from 1999 through 2003. Health officials estimate the problem could be significantly large since most deaths linked to ADHD remain unreported to the FDA. Fifty-four other cases of serious heart problems, including heart attacks and strokes, were also reported. Some of the patients had prior heart problems.

Still, there hasn't been a clear estimate of the scope of side effects. The CDC report, while not a rigorous scientific study, attempts to provide that by using a new hospital surveillance network.

From August 2003 through December 2005, the researchers counted 188 ER visits for problems with the drugs at the 64 hospitals in the network, a representative sample of ERs monitored to spot drug side effects.

Doctors linked use of stimulant ADHD drugs to 73 patients with side effects or allergic reactions. Another 115 accidentally swallowed ADHD pills, including a month-old baby, or took too much.

"These are cases where a young child took someone else's medication or they took too much of their own," CDC epidemiologist Dr. Adam Cohen said of the second group.

Nearly 1 in 5 patients was admitted to the hospital, 1 in 5 needed stomach pumping or treatment with medicines, and 1 in 7 had cardiac symptoms. Sixteen percent of the side effects involved interaction with another drug.

Besides cardiac problems, common symptoms included abdominal pain, rashes and spasms, pain or weakness in muscles, according to Cohen. No patients died.

Extrapolating to all U.S. hospitals, the researchers estimated 3,075 ER visits occur each year.

In another letter in the journal, the heads of the American Psychiatric Association and the American Academy of Child and Adolescent Psychiatry wrote they are concerned a black box warning would discourage use of ADHD drugs, raising patients' risks of academic failure, substance abuse and other problems.

This past February, an FDA drug safety advisory panel voted 8-7 for a black box warning. The next month, another FDA panel instead recommended data on cardiac and other risks go in a new "highlights" section the agency plans to add to the top of drug inserts.

Dr. Marsha Rappley, pediatrics professor at Michigan State University, and two other doctors on the advisory panels believe the vote for a black box was premature.

She said studies show the drugs raise blood pressure and pulse rates a bit, but it's unknown whether that would harm children taking them for years, and that cardiac risks may be higher for adults.

Dr. Steven Nissen, cardiology chief at the Cleveland Clinic, who had pressed for a black box warning at the FDA panel meeting, said ADHD drugs are powerful stimulants and inherently risky. Nissen and other doctors say the drugs are being prescribed to some who don't need them.

This week, the FDA said it is "working diligently" on "labeling changes that we feel accurately reflect the available data and the advice of the committees." The agency declined interview requests.