Alfacalcidol is predicted to increase the risk of toxicity when given with digoxin. Manufacturer advises monitor. Despite being widely prescribed, acute overdosage with digoxin is uncommon. However, digoxin has a low therapeutic index and toxicity is common. Toxicity is the degree to which a chemical substance or a particular mixture of substances can damage an organism. Toxicity can refer to the effect on a whole organism, such as an animal, bacterium, or plant, as well as the effect on a substructure of the organism, such as a cell (cytotoxicity) or an organ such as the liver (hepatotoxicity). - ECG type I sinoatrial block - ECG type II sinoatrial block - ECG atrial tachycardia with block - ECG digoxin toxicity in AF 1 - ECG digoxin toxicity in AF 2 Digoxin toxicity, also known as digoxin poisoning, is a type of poisoning that occurs in people who take too much of the medication digoxin or eat plants such as foxglove that contain a similar substance. What is digoxin toxicity? Digoxin toxicity happens when you have too much digoxin in your body and it becomes harmful. Digoxin is a medicine that is used to treat heart failure or arrhythmias (abnormal heart rhythms). Digoxin is used to treat heart failure, usually along with other medications. It is also used to treat a certain type of irregular heartbeat (chronic atrial fibrillation). Mechanism. The ECG features of digoxin effect are seen with therapeutic doses of digoxin and are due to: Shortening of the atrial and ventricular refractory periods — producing a short QT interval with secondary repolarisation abnormalities affecting the ST segments, T waves and U waves. Chronic digoxin toxicity is diagnosed probabilistically on the basis of the serum digoxin level, the renal function and clinical features, as shown below: Clinical features Probability of digoxin toxicity based on serum digoxin level Digoxin toxicity ECG changes with dysrhythmias. Review of EKG features of digoxin toxicity and cardiotoxicity with example EKG.