Spontaneous hypokalaemia in a man with treated hypertension

An 80 year old man with a history of hypertension, stage 3 chronic kidney disease, and paroxysmal atrial fibrillation presented feeling generally unwell and lethargic. He was taking amiodarone 200 mg, bisoprolol 10 mg, amlodipine 10 mg, and lisinopril 20 mg a day. He did not have a fever and he w...