This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Pharmacology
This antihistaminic drug can cause cardiac arrhythmia at a high dose by blocking cardiac K+ channels. It is most likely to be : 
Select and explain. 
A. Levocetirizine, B. Fexofenadine, C. Astemizole, D. Loratadine
C: Astemizole
Answer: C: Astemizole 
Explanation: None