Which medication is an example of a drug with a narrow therapeutic index?

• A. Aspirin
• B. Ibuprofen
• C. Warfarin
• D. Paracetamol

Answer: (C)

A drug with a narrow therapeutic index is one where there is a small margin between the minimum effective dose and the minimum toxic dose. Warfarin exemplifies this characteristic due to its critical role in anticoagulation therapy; even slight variations in dosage can lead to significant clinical effects.

For patients on Warfarin, maintaining the correct dosage is vital to prevent serious complications such as thrombosis or bleeding. This necessitates regular monitoring of blood levels, often through INR (international normalized ratio) tests, to ensure the medication remains within the therapeutic range.

In contrast, the other medications listed, such as aspirin, ibuprofen, and paracetamol, generally have wider therapeutic indices, allowing for relatively safer dose adjustments without the same level of risk of adverse effects. This distinction helps underscore the importance of careful monitoring and individualized dosing in patients prescribed Warfarin.