TRENTON, N.J. - As more children pop pills for attention deficit and other behavior disorders, new figures show spending on those drugs has for the first time edged out the cost of antibiotics and asthma medications for children.

A 49 percent rise in the use of attention deficit/hyperactivity disorder drugs by children under 5 in the last three years contributed to a 23 percent increase in usage for all children, according to an annual analysis of drug use trends by Medco Health Solutions Inc.

"Behavioral medicines have eclipsed the other categories this year," said Dr. Robert Epstein, Medco's chief medical officer. "It certainly reflects the concern of parents that their children do as well as they can."

Antibiotics still top the list of the most commonly used children's drugs, but parents are paying more for behavioral drugs, such as stimulants or antidepressants, according to the analysis of drug use among 300,000 children under 19.

Medco, the nation's largest prescription benefit manager, was to release the data culled from its customers' usage on Monday.

The most startling change was a 369 percent increase in spending on attention deficit drugs for children under five. That's in part because of the popularity of newer, long-acting medicines under patent, compared with twice-a-day Ritalin and generic versions available for years.

But the use of other behavioral drugs also jumped in the last three years. Antidepressant use rose 21 percent and drugs for autism and other conduct disorders jumped 71 percent, compared to a 4.3 percent rise in antibiotics.

Epstein said 17 percent of total drug spending last year for the group of children under 19 was for behavioral medicines, compared with 16 percent each for antibiotics and asthma drugs, 11 percent for skin conditions and 6 percent for allergy medicines.

Use of such behavior medicines has been controversial, with some experts questioning whether parents and school officials are too eager to medicate disruptive children.

Some experts say no.

"It's not necessarily a bad thing that these medicines are being used more," said Dr. James McGough, associate professor of clinical psychiatry at the UCLA Neuropsychiatric Institute.

McGough said kids on attention deficit drugs tend to avoid substance abuse and other problems and do better in school.

However, McGough said increasing adolescent use of antidepressants is a concern, because there's little proof they work in young people and evidence they may increase suicidal tendencies.

Overall, 5.3 percent of children took some type of behavioral medicine in 2003, including 3.4 percent on attention deficit medicines and 2.3 percent on antidepressants, according to the study. Some children are on both types of drugs. That compares with 44 percent who used antibiotics at some point, 13 percent on asthma medicines and 11 percent who used allergy drugs.

Use of asthma medicines increased 15 percent from 2000 to 2003 and use of medicines for gastrointestinal problems jumped 28 percent, mainly due to new drugs for the stomach gas that gives babies colic.

Dr. Richard L. Gorman, director of the American Academy of Pediatrics' drugs committee, said while there may be "initial overprescribing" of attention deficit disorders, the children are typically taken off the drugs if they don't work.

"Either it's better and everyone's relieved, or nothing happens, the kid's still wild and then the parents say to the school, `We tried this stuff and it didn't work,'" he said.

New attention deficit drugs such as Strattera, Adderall and Concerta require only one morning dose, which helps keep children on an even keel all day and eliminates having to line up to get an afternoon dose from busy school nurses or day-care officials.

The side effects are mainly reduced appetite and growth.

Estimates of how many American children have attention deficit problems vary, from 3 percent to 10 percent. According to the National Center for Health Statistics, the number of children aged 3 to 17 with the disorder rose from 3.3 million in 1997 to 4.4 million in 2002.

Franklin Lakes, N.J.-based Medco said average monthly spending per member was still lowest for those 19 and under, $12.31 a month, compared with $125.58 for those 65 and older.

However, the average cost of a daily dose for one medicine was much higher for children than for senior citizens - $2.12 per day versus $1.29 per day - because many more generic drugs are available for conditions of the elderly.