This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: FMGE 2019, Subject name: Pharmacology
Which anti-asthma drug is avoided with erythromycin? 
Select and explain. 
A. Salbutamol, B. Ipratropium, C. Theophylline, D. Terbutaline.
C: Theophylline
Answer: C: Theophylline 
Explanation: Erythromycin decreases the plasma clearance of theophylline hence may manifest theophylline toxicity. Theophylline follows zero order kinetics. It is metabolised by microsomal enzymes. hence prone to drug interaction. ENZYME INHIBTORS -Agents which inhibit its metabolism are - Erythromycin Ciprofloxacin Cimetidine Oral contraceptive Allopurinol ENZYME INDUCERS - Like rifampicin increases its clearance hence higher dose is required for action. Smoking Phenytoin phenobarbitone