What is digoxin toxicity and what signs should the nurse monitor?

Digoxin toxicity occurs when serum digoxin levels exceed the narrow therapeutic range of 0.5 to 2.0 nanograms per milliliter. Early signs include gastrointestinal symptoms such as anorexia, nausea, and vomiting, and visual disturbances including blurred vision and seeing yellow-green halos around lights. Cardiac signs include bradycardia, premature ventricular contractions, and heart block. Hypokalemia increases the risk of toxicity because digoxin and potassium compete for the same binding sites on the heart muscle.