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
[{'content': 'Which of the following statements about theophylline is TRUE \nSelect and explain. \nA. Its use in asthma has declined because of narrow safety margin, B. Its dose needs to be reduced in the smokers, C. It acts by increasing the formation of cAMP, D. Its plasma half life is longer in children as compared to that in adults', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Theophylline has a narrow therapeutic index. Its use has been declined due to narrow safety margin.\nIt inhibits the enzyme phosphodiesterase and thus decreases the metabolism of cAMP. It does not increase the forma\xadtion of cAMP.\nSmoking is a powerful enzyme inducer. Dose of theophylline should be increased in smokers.\nChildren metabolize theophylline faster than adults whereas elderly metabolize it slowly. Therefore, the half-life of theophylline is shorter in children as compared to adults.', 'role': 'assistant'}]