"Children often react differently to drugs than adults do," said Health and Human Services ( news - web sites) Secretary Tommy Thompson. "We need to conduct testing now to fully understand the effects of these medications in children."

The 12 drugs include azithromycin, an antibiotic that's used to treat different types of bacterial infections, and baclofen, a muscle relaxant used to relieve muscle problems caused by multiple sclerosis or spinal injuries.

Dr. Jane M. Orient, executive director of the Association of Physicians and Surgeons, questioned whether most of the drugs on the list should not be tested in children because of potential risks.

"Safety testing needs to be done, but adults should bear the risks," she said. "Once in use, it would seem that careful aftermarket surveillance of any usage in children, as medically indicated and under the supervision of a personal physician, would be greatly preferable to clinical trials."

The National Institute of Child Health and Human Development developed the list of drugs to be tested in consultation with the Food and Drug Administration ( news - web sites) and experts in pediatric research. It will be updated annually.

The FDA issued regulations in 1998 requiring drug companies to test adult medicines commonly given to children. A federal judge threw out the rule last year, saying Congress never intended to give the agency the power to require such tests.

Congress enacted legislation last year giving drug makers financial incentives for conducting the tests. It also set up a grant program to provide federal dollars for pediatric studies that manufacturers won't do, despite the incentives.

Thompson said tests on the 12 drugs listed Monday will be the first sponsored by the government under that new law. The National Institutes of Health ( news - web sites), which will oversee the tests, has set aside $25 million from its current budget, and the FDA, which will review the test results, has set aside $6.6 million.

Thompson said President Bush ( news - web sites)'s budget request for the fiscal year that begins in October will include another $61.5 million for the testing program.

He said the administration also will ask Congress this year to clearly establish FDA's authority to require drug manufacturers to conduct pediatric clinical trials on new drugs. Legislation requiring such trials was introduced in the Senate last year by Sens. Mike DeWine, R-Ohio, Hillary Rodham Clinton ( news - web sites), D-N.Y., and Chris Dodd, D-Conn.

The 12 drugs listed Monday are no longer under patent. Officials said the tests, which will take about two years for each drug, will be done by private contractors under the supervision of NIH. The contractors have not been selected.