This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Asthma, Subject name: Pharmacology
[{'content': 'Which of the following drugs has been found to be useful in acute severe asthma? \nSelect and explain. \nA. Magnesium Sulphate, B. Anti-leukotrine, C. Cromolyn Sodium, D. Cyclosporine', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Ans. (A) Magnesium sulphate(Ref: Harrison 17th/e p1605)Magnesium sulphate by i.v. or inhalational route has been used for the treatment of acute severe asthma. All other drugs mentioned in the options are used for prophylaxis of asthma.', 'role': 'assistant'}]