Pharmacology TDM is a process where plasma concentration of drug is constantly monitored. Recommended levels of plasma concentration for Theophylline is A 10 - 20 mg / ml B 10 - 45 mg / ml C 4 - 12 mg / ml D 8 - 15 mg / ml 💡 Explanation TDM is a process where plasma concentration of drug is constantly monitored. Recommended levels of plasma concentration for Theophylline is ✓ Correct Answer: D. 8 - 15 mg / ml