Plasma drug monitoring is done for
**Core Concept**
Plasma drug monitoring is a clinical practice aimed at measuring the concentration of a specific drug in a patient's plasma to ensure therapeutic efficacy and minimize toxicity. This process involves analyzing the pharmacokinetic properties of the drug, including its absorption, distribution, metabolism, and excretion (ADME).
**Why the Correct Answer is Right**
Plasma drug monitoring is essential for medications with a narrow therapeutic index, such as antiepileptics, anticoagulants, and certain antibiotics, which require precise dosage adjustments to prevent adverse effects. The concentration of these drugs in plasma is typically measured using techniques like high-performance liquid chromatography (HPLC) or immunoassays. This monitoring allows clinicians to adjust the dosage to achieve optimal therapeutic effects while minimizing the risk of toxicity.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because plasma drug monitoring is not typically performed for over-the-counter medications, which generally have a wider therapeutic index and are less likely to cause toxicity.
**Option B:** This option is incorrect because plasma drug monitoring is not a routine practice for medications with a broad therapeutic index, such as acetaminophen or ibuprofen, which can be safely used at a wide range of doses.
**Clinical Pearl / High-Yield Fact**
One key aspect of plasma drug monitoring is the concept of trough levels, which refer to the lowest concentration of a drug in plasma during its dosing interval. Maintaining a trough level within a therapeutic range is crucial for ensuring the effectiveness of medications like warfarin and phenytoin.
**Correct Answer: C. Medications with a narrow therapeutic index.