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
Most common side effect of 5-HT 3 antagonist drug alosetron is ? 
Select and explain. 
A. Pulmonary fibrosis, B. Cardiac arhythymmias, C. Constipation, D. Headache
C: Constipation
Answer: C: Constipation 
Explanation: Ans. is 'c' i.e., Constipation Alosetron has sometimes caused fatal intestinal side effects including constipation and ischemic colitis.