What is the purpose of therapeutic drug monitoring (TDM)?

• A. To identify the mechanism of drug action.
• B. To assess bioavailability in healthy volunteers.
• C. To optimize efficacy and minimize toxicity by adjusting dosing based on measured concentrations.
• D. To estimate population PK parameters.

Answer: (C)

Therapeutic drug monitoring focuses on tailoring dosing to an individual patient by measuring the drug’s concentration in the blood and adjusting the dose or dosing interval to keep levels within a safe and effective range. This approach recognizes that people vary in how they absorb, distribute, metabolize, and excrete a drug, and that drugs with a narrow therapeutic window can cause toxicity if levels are too high or fail to work if too low. By targeting a specific trough or steady-state concentration, clinicians optimize efficacy while minimizing adverse effects, often with iterative measurements and dose adjustments.

This isn’t about discovering a drug’s mechanism, assessing bioavailability in healthy volunteers, or estimating population pharmacokinetic parameters. Those are about general properties or research methods, whereas TDM is about applying measured concentrations to individualize therapy for better outcomes.