Digoxin × telmisartan

Telmisartan moderately inhibits intestinal P-glycoprotein. Digoxin AUC rises by 20–50%, which may trigger toxicity, especially in older patients and in chronic kidney disease.

Nausea, vomiting, loss of appetite, confusion, yellow-green halos around lights, arrhythmia (bigeminy, AV block). Symptoms appear earlier in older patients and chronic kidney disease.

On telmisartan start, check digoxin levels at 1–2 weeks. In significant chronic kidney disease (clearance below 50 mL/min), reduce digoxin by 25%. In older patients, target 0.5–0.8 ng/mL. Alternatives: losartan or valsartan, with less effect on P-glycoprotein.