This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Endocrinology, Subject name: Pharmacology
[{'content': 'True about atosiban is? \nSelect and explain. \nA. Is an oxytocin receptor antagonist, B. Is an progesterone receptor antagonist, C. Is least effective in inhibiting preterm uterine Contractions, D. Is a anti-tocolytic drug', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Atosiban is a peptide analog of oxytocin that acts as an antagonist at the oxytocin receptors. It is a tocolytic. It suppress uterine contractions and postpones preterm delivery. (Ref.Essentials of medical pharmacology TD Tripathi 6th edition page no.333).', 'role': 'assistant'}]