• Three consecutive MOAA/S scores ≤4 after administration of sedative medication AND completing the procedure without requiring the use of alternative sedative medication AND without requiring manual or mechanical ventilation
  

• Patient's rating of experience after ready for discharge
  
• Principal Investigator's (PI's) rating at end of procedure
  
• Percentage of patients requiring alternative sedative medication
  
• Number of doses/amount of fentanyl administered
  
• Number of doses of study medication administered
  
• Time to sedation, digital rectal examination, start of procedure, reach splenic flexure, hepatic flexure, cecum, end of procedure, and ready for discharge
  
• Percentage of patients requiring repositioning
  
• Percentage of patients whose procedures are interrupted due to inadequate sedation
  
• Time to ready for discharge from end of procedure
  
• Change from baseline DSST score over time during recovery period
  
• Patient's rating at 24 hour post discharge telephone survey
  
• Duration and percent of time when a patient's MOAA/S score is at each level between the first dose of study medications and fully alert and during the procedure
  
• PI's rating of level of sedation prior to initiation of the procedure
  
• Percentage of patients with a mean MOAA/S of 2 to 4 and 0 to 1 during the procedure
  
• MOAA/S over time
  

This is a randomized, double-blind study designed to evaluate the dose-response in the sedation success rate for 4 different initial bolus doses of AQUAVAN following pretreatment with an analgesic, fentanyl, in patients undergoing a colonoscopy. A group of patients will receive midazolam as a reference therapy.

Following completion of pre-procedure assessments, patients will be randomly assigned to 1 of 5 IV treatment groups at an equal allocation ratio (25 patients per arm) on the day of the scheduled procedure. Randomization will be stratified by age and ASA status:

AQUAVAN initial bolus dose 1: 8 mg/kg AQUAVAN initial bolus dose 2: 6.5 mg/kg AQUAVAN initial bolus dose 3: 5 mg/kg AQUAVAN initial bolus dose 4: 2 mg/kg Midazolam initial bolus dose: 0.02 mg/kg

A person skilled in airway management and authorized by the facility in which the colonoscopy is performed (such as a respiratory therapist, a study nurse, or a clinician) must be immediately available during the conduct of the study. All patients will be placed on supplemental oxygen via nasal cannula (4 L/min), and a 12-lead electrocardiogram (ECG), pulse oximeter, and blood pressure monitor prior to administration of study medication. All patients will receive an injection of analgesic pretreatment followed by the administration of sedative medication, as described below. This protocol recognizes 2 distinct phases of sedation: Sedation Initiation and Sedation Maintenance. Assessments will be made to evaluate the patients for levels of sedation, clinical benefit, and adverse events as detailed in the protocol. Blood samples will be collected for pharmacokinetic (PK) analysis, also detailed in the protocol.