The 30-week trial, called MARS (Montelukast or Azithromycin for Reduction of Inhaled Corticosteroids in Childhood Asthma), is part of a national study sponsored by the National Heart, Lung, and Blood Institute.

"This study is important because long-term inhaled steroid use may have side effects, such as reduced growth," said Robert C. Strunk, M.D., professor of pediatrics and the principal investigator of the St. Louis study site.

"Through this study, we will also learn more about the characteristics of children with moderate to severe asthma."

Children who qualify will be assigned to receive either a placebo or one of two drugs approved by the Food and Drug Administration: Zithromax or Singulair.

In adult studies, Zithromax, an antibiotic, and Singulair, an asthma drug, have allowed adults to reduce the amount of inhaled steroids needed to control asthma.

Volunteers will receive 10 health assessments and study medication for free as well as compensation for their time.

Children with severe asthma make up only about 5 percent to 10 percent of children with the disease, according to Strunk.

"But these children have the most problems because of their asthma, take more asthma medications and are more likely to be hospitalized and miss school," he said.

For more information about the study, call 286-1173.