The primary objective of this study is to characterize the safety, and efficacy of Dexmedetomidine (DEX) administered as an intravenous (IV) loading dose followed by a continuous IV infusion in preterm subjects, ages ≥ 28 weeks through < 36 weeks gestational age.

Inclusion Criteria:

1. Initially intubated and mechanically ventilated pediatric subjects in an intensive care setting anticipated to require at least 6 hours of continuous IV sedation.

2. Age: subjects must fit the following age range at screening:

   Preterm subjects ≥28 weeks through <36 weeks, gestational age;

   Note: Gestational age (in weeks) will be calculated as follows: the time elapsed between the first day of the last menstrual period and the day of enrollment.

3. Weight: subject's weight at the time of enrollment must be >1000 g.

4. Subject's parent(s) or legal guardian(s) has/have voluntarily signed and dated the informed consent document approved by the Institutional Review Board (IRB)/Independent Ethics Committee (IEC).

Exclusion Criteria:

1. Neonate subjects with neurological conditions that prohibit an evaluation of sedation such as:

   • Diminished consciousness from increased intracranial pressure.
   • The presence of catastrophic brain injury or other severe mental disorders that would make responses to sedatives unpredictable and/or measurement of the N-PASS unreliable.
   • Subjects with immobility from neuromuscular disease or continuous infusion of neuromuscular blocking (NMB) agents.

2. Subjects with second degree or third degree heart block unless subject has a pacemaker or pacing wires are in situ.

   Note: If subject's status-post Cardio Pulmonary Bypass (CPB) was managed without pacing wires in situ, the subject must not be suspected to be in second degree or third degree heart block at the time of DEX administration.

3. HR < 120 bpm prior to the initiation of DEX.

4. Exposure to any investigational drug within 30 days prior to DEX administration.

5. Previous exposure to DEX as part of an investigational study.

6. In subjects that are ex-utero for less than 72 hours, a maternal history of poly-substance drug abuse, based upon the Investigator's clinical judgment.

7. At the discretion of the Investigator, subjects in whom the risk of DEX treatment is expected to exceed its benefits.

8. Subjects who have a known allergy or contraindication to fentanyl, morphine, MDZ, DEX, or other α-2 agonists.

9. Requirement for medications other than DEX, MDZ, morphine, or fentanyl for sedation and pain control.

10. Screening ALT levels >115 U/L.