**Question:** TDM is a process where plasma concentration of drug is constantly monitored. Recommended levels of plasma concentration for Theophylline is

A. 10-20 μg/mL
B. 10-200 μg/mL
C. 10-20 μg/mL
D. 10-200 μg/mL

**Core Concept:** TDM (Treatment Drug Monitoring) is a process where the plasma concentration of a drug is continuously monitored to ensure that the therapeutic effects of the drug are achieved while minimizing potential side effects. In the context of Theophylline, a drug commonly used for asthma treatment, the therapeutic plasma concentration range is crucial for optimal therapeutic outcomes.

**Why the Correct Answer is Right:** The correct answer, "10-20 μg/mL", represents the therapeutic range for plasma concentration of Theophylline. Theophylline is a methylxanthine drug that increases bronchodilation and suppresses bronchoconstriction in asthma patients. The therapeutic range ensures that the drug is effective in treating asthma symptoms while minimizing potential side effects, such as nausea, vomiting, and headache.

**Why Each Wrong Option is Incorrect:**

A. 10-200 μg/mL: This option is incorrect because it includes an excessive range, both lower and higher than the therapeutic range, leading to potential side effects at higher concentrations and inadequate treatment at lower concentrations.

B. 10-200 μg/mL: This option is also incorrect because it includes an excessive range, similar to option A.

C. 10-20 μg/mL: This option is close to the correct answer but still too narrow, potentially resulting in inadequate treatment due to the narrow therapeutic range.

D. 10-20 μg/mL: This option is the correct answer, as it represents the appropriate therapeutic range for plasma concentration of Theophylline, ensuring effective treatment and minimizing side effects.

**Clinical Pearl:** Monitoring and maintaining the plasma concentration within the therapeutic range of 10-20 μg/mL is crucial for the optimal management of asthma patients on Theophylline therapy. Regular monitoring allows healthcare providers to adjust the dosage of Theophylline accordingly, ensuring that the drug effectively reduces bronchoconstriction while minimizing potential adverse effects.