This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Other topics and Adverse effects, Subject name: Anatomy
Which of the follwing patients is most likely to be treated with intravenous glucagon? 
Select and explain. 
A. A young man who took cocaine and has a blood pressure of 190/110 mm Hg, B. A middle aged man with type II diabetes who has not taken his regular dose of glipizide for last 4 days, C. An old man with severe bradycardia and hypotension resulting from ingestion of overdose of atenolol, D. An old woman with lactic acidosis as a complication of severe infection and shock
C: An old man with severe bradycardia and hypotension resulting from ingestion of overdose of atenolol
Answer: C: An old man with severe bradycardia and hypotension resulting from ingestion of overdose of atenolol 
Explanation: (Ref: KDT 6/e p274) Glucagon is the antidote of b-blocker poisoning. It acts by increasing cAMP in the hea stimulation of glucagon receptors. Cyclic AMP stinulates the hea. Calcium gluconate can also be used for the treatment of b-blocker poisoning.