MSFinals-5081
An 80-year-old man with a history of hypertension, gout, and complex regional pain syndrome is currently recovering from a total hip replacement surgery for a subcapital fracture neck of the femur. He is taking amlodipine 10 mg OD, allopurinol 100 mg OD, pregabalin 150 mg BD, and paracetamol 1g QDS. The patient is using a patient-controlled analgesia (PCA) pump for regular administration of IV morphine. He contacts the ward sister complaining of suprapubic pain and difficulty in passing urine.
Which medication is the most likely cause of these symptoms?