What is therapeutic drug monitoring (TDM) and give an example of a drug commonly monitored?

• A. Measuring drug levels to optimize efficacy and minimize toxicity; example: vancomycin trough or digoxin level.
• B. Measuring patient satisfaction with drug therapy.
• C. Only used for vaccination efficacy.
• D. Used to monitor drug manufacturing quality.

Answer: (A)

Therapeutic drug monitoring is measuring drug levels in a patient’s blood to guide dosing so the drug remains effective while minimizing toxicity. It’s especially important for drugs with narrow therapeutic windows or highly variable pharmacokinetics. By checking levels—often a trough just before the next dose or a peak after dosing—clinicians adjust the dose or dosing interval to hit a target concentration. An example commonly monitored is vancomycin, where trough levels help ensure the drug provides enough exposure to treat infection while reducing kidney toxicity. Digoxin levels are also checked for similar reasons, due to its potential toxicity if concentrations become too high. The other options don’t involve using drug levels to tailor therapy to the patient.