NEW YORK (Reuters Health) May 29 - Tobacco exposure increases leukotriene-related albuterol usage and the response to montelukast in children with asthma, according to a report in the April 24th online issue of the Journal of Allergy and Clinical Immunology.

"The airway response to biological mediators and susceptibility to therapies can differ based on factors such as gender and type of environmental exposure," Dr. Nathan Rabinovitch from National Jewish Medical and Research Center, Denver, told Reuters Health. "Therefore, it's important to tailor the treatment to the individual patient...to maximize efficacy and minimize side effects."

Dr. Rabinovitch and colleagues investigated biological and subject-level predictors of increased individual susceptibility to the effects of cysteinyl leukotrienes and montelukast treatment among 27 school children with asthma.

Increased urine levels of leukotriene E4 (LTE4) were strongly associated with increased albuterol usage, the authors report. Treatment with montelukast virtually eliminated the increased albuterol usage associated with LTE4 levels, the report indicates.

Declines in LTE4-related albuterol usage with montelukast treatment tended to be greater in girls than in boys, the investigators say, and the response to montelukast was significantly greater in children with higher cotinine levels (reflecting exposure to tobacco smoke).

Declines in LTE4-related albuterol usage after montelukast treatment were most apparent among children with higher LTE4:FENO (fractional exhaled nitric oxide) ratios, the researchers note.

"These findings suggest that changes in cysteinyl leukotriene levels (as defined by urinary LTE4 excretion) are related to asthma control," the authors explain. "Among subsets of children with asthma on inhaled corticosteroid therapy, environmental and subject-level characteristics may lead to a distinctive pathogenic pathway predominantly mediated by cysteinyl leukotrienes, and susceptibility to treatments with leukotriene receptor antagonists."

"Based on this study, I would recommend measurement of the LTE4:FENO ratio before starting montelukast in children," Dr. Rabinovitch said. "As in all studies with new findings, it will be important to replicate these findings in other populations and settings. For example, we plan to study whether LTE4:FENO predicts asthma responsiveness in adults as well as children."

J Allergy Clin Immunol 2008.