diltiazem and digoxin

Diltiazem increases digoxin serum concentrations by inhibiting P-glycoprotein (P-gp) mediated renal tubular secretion of digoxin, reducing its renal clearance. This pharmacokinetic interaction can occur within days of initiating diltiazem therapy.

Elevated digoxin levels may lead to clinical toxicity, including nausea, vomiting, bradycardia, and various cardiac arrhythmias, which can be life-threatening. Symptoms may appear even at therapeutic digoxin doses.

If co-prescription is necessary, monitor serum digoxin concentrations and clinical response closely, especially after starting or stopping diltiazem. Consider a lower digoxin dose and adjust based on levels and renal function. Monitor heart rate, blood pressure, and ECG for signs of toxicity.

This interaction is well documented in pharmacokinetic studies and numerous case reports. The effect is more pronounced in patients with renal impairment or those on higher diltiazem doses.