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 high dose by blocking cardiac K +  channels. It is most likely to be: 
Select and explain. 
A. Levo-cetrizine, B. Fexofenadine, C. Astemizole, D. Loratidine
C: Astemizole
Answer: C: Astemizole 
Explanation: None