digoxin and erythromycin

Erythromycin inhibits the P-glycoprotein efflux transporter in the renal tubules and the intestine, which reduces the renal and biliary clearance of digoxin and may increase its absorption. It may also reduce the metabolism of digoxin by gut bacteria in some individuals.

Plasma digoxin concentrations can rise substantially, typically within a few days, increasing the risk of digoxin toxicity. Symptoms include nausea, vomiting, visual disturbances, arrhythmias, and, in severe cases, heart block or ventricular tachycardia.

Monitor serum digoxin concentrations and renal function before and after starting erythromycin. Watch for signs of digoxin toxicity. A digoxin dose reduction may be needed, and alternative antibiotics should be considered if possible. If erythromycin is used, adjust the digoxin dose according to the measured levels.

This interaction is well documented in clinical case reports and pharmacokinetic studies. The effect is more pronounced with intravenous erythromycin and in patients with renal impairment or pre-existing high digoxin levels.