Which of the following drugs should be monitored for toxicity in patients taking thiazides?

Monitoring for toxicity is particularly important when patients are taking lithium alongside thiazide diuretics. Thiazides can lead to an increase in lithium levels by decreasing its renal clearance. Since lithium has a narrow therapeutic window, even small elevations in blood levels can result in toxicity, which includes symptoms such as nausea, tremors, confusion, and in severe cases, renal failure or seizures. Thus, regular monitoring of lithium levels is essential to ensure they remain within a safe range when thiazides are used, helping to prevent potentially dangerous side effects.

Other medications listed, while important to manage, do not interact with thiazides to the same extent regarding toxicity monitoring. Warfarin, for instance, is monitored primarily through INR levels to manage anticoagulation but does not have a direct toxic relationship with thiazides. Similarly, while aspirin and clopidogrel are important for their respective indications in cardiovascular diseases, they do not require increased monitoring for toxicity due to thiazide use. Therefore, the focus on lithium is crucial for patient safety when combined with thiazide diuretics.