• The percent of patients not requiring midazolam for rescue sedation based on achieving and/or maintaining an Observer's Assessment of Alertness/Sedation Scale (OAA/S) score < 4
  

• Total amount (mg) of rescue midazolam required to achieve and/or maintain sedation (OAA/S score < 4)
  
• time from onset of study drug infusion to first dose of rescue midazolam
  
• percentage of subjects who convert to alternative sedative and/or anesthetic therapy due to failure of treatment with study drug and rescue
  
• time to recovery and readiness for discharge from Post-Anesthesia Care Unit (PACU)
  
• total amount of fentanyl required for pain control
  
• anesthesiologist assessment of ease of management
  
• subject cooperation
  
• incidence of post-operative nausea and vomiting in the PACU
  
• subject satisfaction and anxiety assessed 24 hours after study drug
  

Monitored anesthesia care (MAC) is a specific anesthesia service that involves an anesthesiologist administering sedatives and analgesics to a patient while monitoring his/her vital signs. MAC is often used to supplement local and regional anesthesia for non-intubated patients undergoing non-invasive procedures and minor surgery. The goal of MAC is to relieve anxiety by inducing a minimally depressed level of consciousness while the patient is able to continuously and independently maintain a patent airway and to respond appropriately to verbal commands.

Respiratory depression is the major concern with most of the medications (midazolam, fentanyl, propofol) currently used for MAC. There is clearly an unmet need for a sedative agent that can safely be used during MAC in both healthy and high risk populations with limited adverse side effects. A medication that can attenuate anxiety and the stress response associated with surgery and procedures without causing respiratory depression is highly desirable. A medication that reduces the total amount of opioids administered during a procedure could substantially reduce complications. Such a medication could be used either alone or in combination with other agents, thereby reducing the dose and side effects of the other agents.

Dexmedetomidine (DEX) has sympatholytic, sedative, analgesic, and anxiolytic effects that attenuate the catecholamine response to perioperative stress.

DEX has not been associated with respiratory depression when used alone, despite sometimes deep levels of sedation.

An estimated 325 patients (260 DEX, 65 PBO) requiring MAC sedation for an elective surgery/procedure will be randomized at approximately 25 investigative sites.