A 77-year-old man undergoes surgery for a fractured neck of femur. Post-operatively, he develops delirium, becoming acutely confused, agitated, and experiencing visual hallucinations. His observations are stable, and routine blood tests including FBC, U&Es, LFTs, Calcium, TFTs, and CRP are normal. Urine dipstick is negative. What is the most appropriate initial pharmacological management if non-pharmacological measures fail and he is severely distressed or poses a risk?