Leukotriene (LT)‐receptor antagonist is more effective in asthmatic patients with a low baseline ratio of urinary LTE4 to 2,3‐dinor‐6‐keto‐prostaglandin (PG)F1α

Background: To test the hypothesis that urinary levels of arachidonic acid metabolites may be a predicting factor of the effects of pranlukast, a selective leukotriene (LT) antagonist, on chronic adult asthma, we investigated the relationship between its clinical efficacy and urinary eicosanoid levels. Methods: An open, multicenter trial was conducted involving 38 stable moderate and severe asthmatic patients (mean percent predicted FEV1 was 71%). All patients received pranlukast (225 mg twice daily) for 4 weeks after a 2-week run-in period. Urinary levels of LTE4, 11-dehydro-thromboxane (TX) B2, 2,3- dinor-6-keto-prostaglandin (PG) F1α, and creatinine were measured in 3-h urine collected on day 1 of the treatment. The responder was defined by an improvement of asthma symptom scores and peak expiratory flow rate (PEFR). Results: One patient was excluded because of an adverse effect, nausea. Thirteen out of 37 subjects were responders and 24 were nonresponders. There were no significant differences in patients' backgrounds and urinary arachidonate levels between the two groups. The urinary LTE4 to 2,3-dinor-6-keto-PGF1α ratio in the responder was significantly lower (P=0.01) than that in the nonresponder. In all patients, a significant inverse correlation was revealed between the baseline urinary LTE4/2,3-dinor-6-keto-PGF1α ratio and the improvement of PEFR in the morning (r=−0.43, P=0.007). Conclusions: These data suggested that the urinary ratio of LTE4 to 2,3-dinor-6-keto-PGF1α might be one of the predictive markers of the clinical efficacy of this LT-receptor antagonist in asthmatic subjects.