Digoxin toxicity is a poison

Poison

In the context of biology, poisons are substances that can cause disturbances to organisms, usually by chemical reaction or other activity on the molecular scale, when a sufficient quantity is absorbed by an organism....

ing that occurs when excess doses of digoxin

Digoxin

Digoxin INN , also known as digitalis, is a purified cardiac glycoside and extracted from the foxglove plant, Digitalis lanata. Its corresponding aglycone is digoxigenin, and its acetyl derivative is acetyldigoxin...

 (from plants of the genus Digitalis

Digitalis

Digitalis is a genus of about 20 species of herbaceous perennials, shrubs, and biennials that are commonly called foxgloves. This genus was traditionally placed in the figwort family Scrophulariaceae, but recent reviews of phylogenetic research have placed it in the much enlarged family...

) are consumed acutely or over an extended period. The classic features of digoxin toxicity are nonspecific: fatigue, blurred vision, change in color vision (eg. "yellow" vision"), anorexia, nausea, vomiting, diarrhea, abdominal pain, headache, dizziness, confusion, delirium.

Characteristic EKG changes include bradycardia (the most frequent vital sign abnormality in toxicity), a prolonged PR interval

PR interval

In electrocardiography, the PR interval is measured from the beginning of the P wave to the beginning of the QRS complex. It is usually 120 to 200 ms long. On the usual 25 mm/s ECG tracing, this corresponds to 3 to 5 small boxes. The PR interval reflects the time the electrical impulse takes to...

. Anaccelerated junctional rhythm

Junctional rhythm

Junctional rhythm describes an abnormal heart rhythm resulting from impulses coming from a locus of tissue in the area of the atrioventricular node, the "junction" between atria and ventricles....

 or bidirectional ventricular tachycardia

Ventricular tachycardia

Ventricular tachycardia is a tachycardia, or fast heart rhythm, that originates in one of the ventricles of the heart...

 suggests digoxin toxicity until proven otherwise.

Classification

Digoxin toxicity is often divided into acute or chronic. The therapeutic level for digoxin is 0.5-0.8 ng/mL. Low serum potassium increases the risk of digoxin toxicity and cardiac dysrhythmias. The classic arrhythmia is a paroxysmal atrial tachycardia with block. Digoxin toxicity occurs because it is very easy to overdose. Overdose commonly occurs because it's therapeutic effect works only within a very narrow window. The most common source of digoxin is from the Foxglove plant.

Symptoms

Symptoms include hypersalivation, fatigue, nausea/vomiting, changes in heart rate and rhythm, loss of appetite (anorexia), diarrhea, visual disturbances (yellow or green halos around objects), confusion, dizziness, nightmares, agitation, and/or depression, as well as a higher acute sense of sensual activities.

Treatment

The primary treatment of digoxin toxicity is digoxin immune Fab

Digoxin Immune Fab

Digoxin Immune Fab is the generic name for an antidote for overdose of digitalis. It is made from immunoglobulin fragments from sheep who have already been immunized with a digoxin derivative, digoxindicarboxymethoxylamine...

. Digoxin should not be given if the apical heart rate is below 60 BPM (beats per minute).

Other treatment that may be tried to treat life-threatening arrhythmias, until digoxin Immune Fab is acquired are magnesium

Magnesium

Magnesium is a chemical element with the symbol Mg, atomic number 12, and common oxidation number +2. It is an alkaline earth metal and the eighth most abundant element in the Earth's crust and ninth in the known universe as a whole...

, phenytoin

Phenytoin

Phenytoin sodium is a commonly used antiepileptic. Phenytoin acts to suppress the abnormal brain activity seen in seizure by reducing electrical conductance among brain cells by stabilizing the inactive state of voltage-gated sodium channels...

, and lidocaine

Lidocaine

Lidocaine , Xylocaine, or lignocaine is a common local anesthetic and antiarrhythmic drug. Lidocaine is used topically to relieve itching, burning and pain from skin inflammations, injected as a dental anesthetic or as a local anesthetic for minor surgery.- History :Lidocaine, the first amino...

.

Atropine is also used in cases of bradyarrhythmias.