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.