Which agent is usually monitored for its narrow therapeutic index?

The agent that is typically monitored for its narrow therapeutic index is digoxin. A narrow therapeutic index indicates that there is a small margin between the minimum effective dose and the minimum toxic dose of a medication. This necessitates careful monitoring to ensure that drug levels remain within a safe and effective range.

Digoxin is commonly used in the treatment of heart failure and certain types of arrhythmias, and due to its pharmacokinetics, the serum levels can be influenced by factors such as renal function, interactions with other medications, and electrolyte imbalances. Because of these variables, digoxin requires regular monitoring of serum drug levels along with patient symptoms to avoid toxicity, which can lead to serious complications, including arrhythmias and gastrointestinal disturbances.

In contrast, warfarin, while also having a narrow therapeutic index, is managed through INR monitoring rather than routine serum levels. Ibuprofen and amoxicillin have wider therapeutic indices and do not require the same level of monitoring, focusing instead on clinical response and side effects. This distinction emphasizes why digoxin is primarily associated with the need for monitoring due to its risk of toxicity when serum levels stray outside of the therapeutic range.