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
Which of the following agent increases blood levels of theophylline? 
Select and explain. 
A. Erythromycin, B. Rifampicin, C. Tobacco, D. Ethanol
A: Erythromycin
Answer: A: Erythromycin 
Explanation: Factors Affecting Clearance of Theophylline: Increased clearance: Enzyme induction (mainly CYP1A2) by co-administered drugs (e.g., rifampicin, barbiturates, ethanol) Smoking (tobacco, marijuana) CYP1A2 induction High-protein, low-carbohydrate diet Barbecued meat Childhood Decreased clearance: CYP inhibition (cimetidine, erythromycin, ciprofloxacin, allopurinol, fluvoxamine, zileuton, zafirlukast) Congestive hea failure Liver disease Pneumonia Viral infection and vaccination High-carbohydrate diet Old age