With which medication should caution be exercised when using digoxin?

Caution should be exercised when using digoxin with diltiazem due to the potential for increased serum digoxin levels. Diltiazem is a non-dihydropyridine calcium channel blocker that can inhibit the metabolism of digoxin, primarily through effects on the cytochrome P450 system. This inhibition can lead to increased bioavailability of digoxin, raising the risk of digoxin toxicity, which may present with symptoms such as nausea, vomiting, visual disturbances, and arrhythmias.

While the other medications listed, including amlodipine, lisinopril, and captopril, have their own interactions and considerations, they do not significantly affect digoxin levels in the same way diltiazem does. Amlodipine primarily acts as a vascular smooth muscle relaxant and does not have a significant impact on digoxin metabolism. Lisinopril and captopril, both ACE inhibitors, are used to manage heart failure and hypertension without causing clinically significant interactions with digoxin. Thus, the caution with diltiazem is particularly highlighted due to its impact on digoxin's pharmacokinetics.