A Safety and Efficacy Study of Dexmedetomidine in Patients Requiring Sedation During Monitored Anesthesia Care (MAC)

Inclusion Criteria: * Adult (≥18 years of age) * American Society of Anesthesiologists (ASA) Physical Status I, II, III, or IV. * If female, subject is non-lactating and is either: 1. Not of childbearing potential, defined as post-menopausal for at least 1 year or surgically sterile due to bilateral tubal ligation, bilateral oophorectomy or hysterectomy. 2. Of childbearing potential but is not pregnant at time of baseline and is practicing one of the following methods of birth control: oral or parenteral contraceptives, double-barrier method, vasectomized partner, or abstinence from sexual intercourse. * Subject requires monitored anesthesia care (MAC) in an operating room (OR) or procedure room with an anesthesiologist in attendance. * Subject requires one of the following types of elective surgeries/procedures expected to take longer than 30 minutes: * Orthopedic * Ophthalmic * Plastic * Vascular stents * Breast biopsies * AV fistulas * Excision of lesion. * Subject requires local anesthetic block. * Subject (or subject's legally authorized representative) has voluntarily signed and dated the informed consent document approved by the Institutional Review Board. Exclusion Criteria: * Subject has received general anesthesia within 7 days prior to study entry, has received any experimental drug within 30 days prior to study drug administration, or has been previously enrolled in this study. * Subject requires endotracheal intubation or laryngeal mask airway (LMA) * Subject has central nervous system (CNS) disease with an anticipated potential for increased intracranial pressure, an uncontrolled seizure disorder, and/or known psychiatric illness that could confound a normal response to sedative treatment. * Subject requires epidural or spinal anesthesia. * Subject has received treatment with an alpha-2 agonist or antagonist within 14 days of the scheduled surgery/procedure. * Subject for whom opiates, benzodiazepines, dexmedetomidine, or other alpha-2 agonists are contraindicated. * Subject has received an intravenous (IV) opioid within one hour, or a by mouth (PO)/intramuscular (IM) opioid within 4 hours, of the start of study drug administration. * Subject has acute unstable angina, acute myocardial infarction documented by laboratory findings in the past 6 weeks, heart rate \<50 bpm, systolic blood pressure (SBP) \<90 mmHg, or third-degree heart block unless patient has a pacemaker. * Subject has known elevated serum glutamic pyruvic transaminase (SGPT/Alanine aminotransferase \[ALT\]) and/or serum glutamic oxaloacetic transaminase (SGOT/aspartate Aminotransferase \[AST\]) values of ≥2 times the upper limit of normal within the 2 months prior to screening, and/or a history of liver failure. * Subject has any other condition or factor which, in the Investigator's opinion, might increase the risk to the subject.