Respiratory syncytial virus (RSV) bronchiolitis is the most common cause of pneumonia and bronchiolitis in infants and accounts for one in six infant hospitalizations. Acute infections with RSV bronchiolitis often are followed by periods of reactive airway disease, perhaps partly because of the release of leukotriene compounds, which can cause bronchial obstruction, mucosal edema, and bronchial hyperresponsiveness. The Study Group on Montelukast and Respiratory Syncytial Virus conducted a randomized, double-blind, placebo-controlled trial of montelukast for post-RSV reactive airway disease.

During a four-week treatment period, 130 infants from three to 36 months of age were randomized to receive montelukast or placebo. The median age was nine months (the mean age of the typical infant with RSV is three months). Children with documented asthma were not eligible. A total of 116 infants completed the required treatment and initial follow-up, and 87 infants completed the two-month follow-up. Primary end points were 24-hour symptom-free periods scored by the following criteria: night cough, day cough, wheezing, dyspnea, and activity level. Secondary outcomes were exacerbations, emergency department visits, and hospitalizations.

Acute RSV symptoms were moderate to severe; postbronchiolitis symptoms were mild. The treatment benefit became apparent after two weeks of treatment. Infants in the treatment group had five more symptom-free days and nights than infants in the placebo group (six of 28 days for treatment, one of 28 days for placebo). The treatment group experienced a significant reduction in daytime cough and delayed time to exacerbations. However, there were no significant differences at the two-month follow-up assessment.

The authors conclude that treatment with leukotriene-receptor antagonists leads to improved clinical symptoms in RSV post-bronchiolitis. Benefits likely are due to effects on reactive airway disease after bronchiolitis rather than effects on the acute inflammatory phase. The authors also note that the average symptom score was mild in both groups, leaving limited room for improvement following treatment.

editor's note: A report released in January 2003 by the Agency for Healthcare Research and Quality concluded that there is insufficient evidence demonstrating the effectiveness of a number of RSV treatments, including inhaled bronchodilators, inhaled corticosteroids, and inhaled epinephrine. Larger, better-designed trials of these interventions are recommended before their efficacy can be established. This trial shows promise for a new type of treatment for the sequelae of RSV. In this case, larger prospective trials of a more diverse and symptomatic population are needed to better evaluate leukotriene-receptor antagonist treatment after RSV infection.—c.c.