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
Fastest acting antithyroid drug is? 
Select and explain. 
A. Potassium iodide, B. Propylthiouracil, C. Carbimazole, D. Cholestyramine
A: Potassium iodide
Answer: A: Potassium iodide 
Explanation: Ans. is 'a' i.e., Potassium iodide o Iodine is the fastest acting thyroid inhibitor.