New York ? When Christy Olson’s daughter developed asthma as a toddler 12 years ago, she was reluctant to put her on prescription drugs.

“I was so worried about side effects. I didn’t want to give it to her unless I had to,” said Olson, who lives in Rochester, Minn., and is a nurse herself. She decided it was a necessary move, and her daughter, now 15, still takes medicine for her condition.

While parents then and now are often nervous about medicating children, it is becoming more common. Use of prescription drugs is growing faster among children than it is among senior citizens and baby boomers, the two traditionally high consumer groups, according to a new study.

Spending on prescription drugs for those under 19 grew 28 percent last year, according to the survey by Medco Health Solutions, a Franklin, N.J.-based pharmacy benefits manager.

Meanwhile, spending per patient rose 23 percent for those between the ages of 25 and 49 and less than 10 percent for those above 65.

Children are also spending 34 percent more time on medication than they were five years ago, the study found.

Treating children is still relatively inexpensive, costing an average of $84.72 per patient each year. That compares to an average expense of $944.40 per year for people aged 65 to 79.

The Centers for Medicare and Medicaid Services, a government agency, estimates that overall spending on prescription drugs rose 16.4 percent to $142 billion last year.

Among children, the most prescribed drugs were for allergies, asthma and infections. Prescriptions for Ritalin and other medicines for neurological and psychological disorders were also substantial a finding that renewed concern among some experts who worry that such drugs may be over-prescribed for children.

Some doctors also were alarmed that spending on prescription drugs to treat heartburn and other gastrointestinal disorders surged 660 percent over five years, according to the study. The jump was seen as linked to the increasing number of overweight children in the United States.

Some of the findings on prescription drugs mirrored trends seen in disease patterns. For example, the incidence of asthma and allergies are generally increasing, so doctors said it wasn’t surprising that children’s’ prescriptions for such ailments would also grow.

“It is good news that more kids are getting treated for asthma because it means less trips to emergency rooms and hospitals,” said Dr. Robert Epstein, chief medical officer of Medco Health.

About 7 percent of children have asthma and 25 percent have allergies, approximately double the incidence 25 years ago, according to Dr. Michael Blaiss, a pediatrician who specializes in such ailments.

The survey also found that spending on antibiotics among children increased 42 percent. Doctors say antibiotic resistance is a widespread problem.

Spending on drugs for Attention Deficit Hyperactivity Disorder increased 122 percent over the past four years and accounted for 8 percent of the total spent on prescription drugs for children, up from 7 percent in 1997. Spending for depression medicines held steady at 5 percent of the total.

The vast majority of prescription drugs are developed for adults, and drug makers are not obliged to test them on children. In 1997, Congress passed legislation that gave drug companies an additional six months of market exclusivity if they tested their drugs on children.