This is a prospective study of montelukast efficacy in addition to standard treatment of status asthmaticus in children from 2-5 years old who are in the PICU. Children who meet eligibility requirements will be randomized to receive a rapid-dissolving oral dose of montelukast or placebo. Once enrolled, a baseline modified Wood's-Downes clinical asthma severity score will be recorded pre and post completion of a standard nebulized albuterol treatment of 0.15 mg/kg/dose (min2.5mg/dose). Patients who are able will have FEV1 measurements obtained at predetermined intervals for determination of clinical asthma severity score. Blood samples for PK analysis will be collected prior to study drug administration and at predetermined time intervals to determine the plasma level of montelukast. In addition, a blood sample will be obtained for genetic study of polymorphisms of CYP3A4, CYP3A5, and CYP2C9.