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
The drug of choice for the treatment of Thyrotoxicosis during pregnancy is ? 
Select and explain. 
A. Carbimazole, B. Iodine therapy, C. Propylthiouracil, D. Metimazole
C: Propylthiouracil
Answer: C: Propylthiouracil 
Explanation: Ans. is 'c' i.e., Propylthiouracil o Both carbimazole and propylthiourcil can be used during pregnancy, but propyl-thiouracil is the drug of choice because its greater protein binding allows low doses of propylthioracil to be transferred across the placenta and therefore less chance of hypothyroidism. o Historically, prophylthiouracil has been preferred over methimazole because transplacental passage was thought to be lower; However, according to recent studies, both propylthiouracil and methimazole cross the placenta equally and either may be used safety in the pregnant patient. Note : However, if you will have to choose one option, prophylthiouracil is still the best because all other books still mention prophylthiouracil as the DOC in pregnancy.