The purpose of this study is to evaluate the efficacy and the safety of DA-9501 (Dexmedetomidine) in sedation during the surgery or medical procedure without intubation under monitored sedation care.

Phase III, randomized, placebo controlled, double blind, parallel comparative study (Therapeutic confirmatory trial), to evaluate the efficacy and the safety of Dexmedetomidine in non-intubated patients who require sedation during surgery or medical procedure under monitored sedation care.

Inclusion Criteria:

1. Patient has signed and dated the Informed Consent after the study had been fully explained.

2. Patient is male or female, at least 20 years of age when the Informed Consent is obtained.

3. American Society for Anesthesiologists (ASA) I to III Class at the preoperative diagnosis.

4. New York Heart Association (NYHA) classification is I to III (Only patients who need classification of cardiac performance.)

5. Patient who requires sedation during the following elective surgery or procedure which require ≥30mins (expected time) without intubation under monitored sedation care.

   - Orthopedic, Otorhinologic, Oral surgeries, AV fistulas, Plastic, Excision of lesion, Breast biopsy, Catheter ablation, Vascular stents and AV shunt

6. Patient who requires local or regional anesthesia.

Exclusion Criteria:

1. Patient who underwent general anesthesia within 7 days, or who received other study drugs within 30 days from the date of consent.
2. Patient with <92% SpO2 at the physical examination prior to the study drug administration, or ventilatory failure which requires intubation or Laryngeal Mask.
3. Patient with central nervous system pathology which may lead to increased intracranial pressure, uncontrolled seizures, psychiatric disorder which may be confused with the response to sedation treatment.
4. Patient who require neurosurgical or cerebrovascular catheter procedures or interventions.
5. Patient who require general anesthesia, epidural anesthesia or spinal anesthesia for surgery or procedure.
6. Patient who receives treatment by alpha-2 agonists or alpha-2 antagonists within seven days of scheduled surgery or procedure.
7. Patient in whom opioids, DA-9501 or other alpha-2 agonists, or drugs which may be used in the study are contraindicated.
8. Patient diagnosed unstable angina or acute myocardiac infarction within 6 weeks from the date of consent.
9. Patient whose heart rate less than 50 bpm, systolic blood pressure less than 90 mm Hg by the physical examination prior to the study drug administration.
10. Patient has third degree heart block, unless the patient has a pacemaker.
11. Patient who has experienced an increase in alanine transaminase (ALT) and/or aspartate aminotransferase (AST) more than double the upper normal limit within 2 months of the date of consent, or who has a history of liver insufficiency.
12. Pregnant or lactating woman.
13. In the Investigator's or subinvestigator's opinion, patient has any symptom or factor, which might increase risk to the patient by conducting the study or preclude obtaining satisfactory study data.