This study proposal will determine the pharmacokinetics (PK) of montelukast (cysteinyl leukotriene receptor-1 or CysLT1 inhibitor) in very low birth weight (VLBW) infants between 500 - 1500g birth weight at risk for developing bronchopulmonary dysplasia (BPD). Montelukast (Singulair) is a FDA approved specific CysLT1 antagonist widely used clinically in the prophylaxis of asthma in children older than 12 months of age and blocks leukotriene signaling in the lung. BPD shares some pathogenic mechanisms with asthma, however Cysteinyl LT receptor blockade has not been studied in preterm infants. Montelukast is metabolized by the cytochrome P450 system which is immature in the preterm infant and hence the need for this study. The investigators' long-term hypothesis is that inhibition of leukotriene signaling in the VLBW preterm lung will decrease inflammation, remodeling and the incidence of BPD. The data will be used to design future efficacy trials of Montelukast in the prevention of bronchopulmonary dysplasia.