A 75-year-old man is admitted with acute confusion. He has a background of hypertension and BPH. He was recently started on a new medication by his GP. His examination is unremarkable apart from the confusion. Routine bloods including FBC, U&Es, LFTs, Calcium, Glucose, and TFTs are normal. Urine dipstick is negative. CT head is normal. Which of the following medications is most likely to be causing his confusion?