Major
Digoxin × diltiazem
Cardiac glycosides (digitalis)×Calcium channel blocker, non-DHP (benzothiazepine derivative)
Mechanism
Diltiazem blocks intestinal P-glycoprotein – a key digoxin absorption route. Digoxin plasma levels rise by 20–30%. Diltiazem also slows AV conduction.
Symptoms
Nausea, anorexia, visual disturbances (yellow-green halos around lights), arrhythmias ranging from premature beats to ventricular tachycardia. Older adults: confusion, dizziness. Symptoms appear within 1–2 weeks of co-administration.
Management
When diltiazem starts, reduce digoxin by 25%; check level at 1 week. Alternatives: amlodipine (no P-glycoprotein effect) or a beta-blocker for rate control.
Check the full regimen, not just this pair
Opens the checker with these two drugs prefilled. Add the rest of the regimen and recompute additive risks.