In a patient taking Digoxin, which substance should be avoided?

• A. Calcium Chloride
• B. Potassium chloride
• C. Sodium bicarbonate
• D. Magnesium sulfate

Answer: (A)

Calcium-containing substances should be avoided with digoxin because they raise intracellular calcium, which can magnify digoxin’s effects on the heart and increase the risk of dangerous arrhythmias. Digoxin inhibits the Na+/K+ ATPase, causing more calcium to remain inside cardiac cells. Adding calcium salts like calcium chloride pushes calcium levels higher, potentially triggering ectopic beats, AV conduction disturbances, or ventricular arrhythmias, i.e., digoxin toxicity.

Other substances aren’t as directly contraindicated with digoxin in ordinary situations. Potassium management is important because low potassium can enhance digoxin binding and toxicity, but potassium itself isn’t inherently contraindicated. Sodium bicarbonate and magnesium have roles in specific clinical contexts and aren’t universally avoided with digoxin.