This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Cardiovascular system, Subject name: Pharmacology
Anti arrhythmic drug is 
Select and explain. 
A. Phentolamine, B. Phenobarbitone, C. Procainamide, D. Pentamidine
C: Procainamide
Answer: C: Procainamide 
Explanation: Refer kDT 7/e p 529 Phentolamine is a synthetic imidazoline with alpha-adrenergic antagonist activity. As a competitive alpha-adrenergic antagonist, phentolamine binds to alpha-1 and alpha-2 receptors, resulting in a decrease in peripheral vascular resistance and vasodilatation. Phenobarbital belongs to a class of drugs known as barbiturate anticonvulsants/hypnotics. Pentamidine is an antimicrobial medication used to treat African trypanosomiasis, leishmaniasis, babesiosis, and to prevent and treat pneumocystis pneumonia in people with poor immune function