This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Respiratory system, Subject name: Pharmacology
Drugs which increase level of theophylline include: 
Select and explain. 
A. chloramphenicol, B. Cimetidine, C. Allopurinol, D. All of the above
D: All of the above
Answer: D: All of the above 
Explanation: Drugs which inhibit theophylline metabolism and increase its plasma level are-erythromycin, ciprofloxacin, cimetidine, oral contraceptives,allopurinol, chloramphenicol- all enzyme inhibitors dose should be reduced to 2/3rds of the usual dose KD TRIPATHI Page No:227