Review Question - QID 214863

A 33-year-old man presents to the emergency department after a motor vehicle collision. He was the front seat restrained passenger in a head-on collision at 45 miles per hour. He is having 10/10 left hip pain. His medical history is unremarkable and he takes no medications. His temperature is 97.5°F (36.4°C), blood pressure is 139/99 mmHg, pulse is 128/min, respirations are 25/min, and oxygen saturation is 99% on room air. Physical exam reveals a shortened and internally rotated right hip. A radiograph of the hip and pelvis is shown in Figure A. The patient is given a medication prior to applying traction to the leg. Shortly after administration of this medication, the patient demonstrates a rotary nystagmus followed by a calming effect with minimal patient response when significant force is applied to his leg. Which of the following is the mechanism of the medication administered?