A 62-year-old male with a 10-year history of hepatitis B presents with hematemesis, melena, and subsequent clouding of consciousness. Examination reveals: BP 80/50 mmHg, icteric sclera, slurred speech, loss of orientation, decreased calculation ability, hallucinations, reversed sleep-wake cycle, flapping tremor (asterixis), increased muscle tone (hypertonia), abnormal electroencephalogram (EEG), hemoglobin 40 g/L, blood pH 7.48, serum potassium 2.8 mmol/L, and elevated blood ammonia. If the patient develops agitation, which medication should be administered?