Inclusion Criteria:

• Participant's parent/legal guardian must give written informed consent and written assent must be obtained form the subject prior to study participation.

  1. Obtain consent of the parent/legal guardian using a signed consent form;
  2. Obtain assent form minors between the ages of 7-13 using a signed assent form;
  3. Obtain assent from minors between the ages of 14-17 by having the subject sign the consent formed signed the parent / legal guardian (Or based on the assessment by the Primary Investigator that the patient is unable to comprehend the study as written in the consent form document, the patient may document assent by signing the assent form).
• Participant, male or female, must be 6 to 18 years of age.
• Participant must have a history of reactive airway disease (RAD) or asthma and must currently be admitted for an acute exacerbation of RAD or asthma.
• Primary physician must believe that patient would benefit from improved bronchodilation and improvement in clinical asthma severity score.

• Participant must have received standard therapy for status asthmaticus:

  1. Oxygen as needed
  2. >3 nebulized albuterol treatments of at least 2.5mg/dose
  3. Methylprednisolone or prednisone loading dose of 2mg/kg
  4. Ongoing methylprednisolone therapy @ 0.5mg/kg every 6 hours
• Participant must have received steroids at least 6 hours prior to their inclusion, and must still require nebulized albuterol at least every 2 hours, as determined by PICU team in accordance with the PICU standard for evaluating and treating patients with RAD or asthma exacerbations.
• Participant must have an indwelling catheter in place from which to obtain blood specimens. Catheter may be peripheral or central, arterial or venous.

Exclusion Criteria:

• Known hypersensitivity to montelukast
• Chronic lung disease other than RAD or asthma
• Known renal disease
• Known hepatic disease
• Cardiac or pulmonary congenital anomalies
• Known immunologic disorders other than allergy and atopy
• Other explanations for respiratory distress
• Use of leukotriene modifiers within 2 weeks of the acute presentation
• Pregnant females
• Intubated patients
• Inability to participate in portable spirometry for FEV1 measurement