Cardiac Glycosides

Cardiac glycosides, or cardenolides are naturally occurring plant toxicants that primarily affect the heart. Digitalis cardonlides (digitioxin and digoxin) and yellow oleander are the leading sources of cardiac glycoside poisoning.

Cardioactive glycosides have ionotropic properties that enable them to increase the myocardial contractility without proportionally increasing the rate of oxygen consumption. For this reason, cardio glycosidic plants are commonly used in the treatment of heart failure and cardiac arrhythmia. Digitalis is the genus name for the family of plants that provides the majority of pharmacologically useful cardiac glycosides. Cardiac glycosides that have been elaborated by plants may be referred to as ‘cardenolides’.

Cardiac glycosides function by inhibiting the intercellular sodium-potassium pumps to prevent the extrusion of sodium. Raised sodium levels derange the action of the sodium-calcium pump leading to an increased intracellular calcium concentration. Elevated intracellular calcium levels within the sarcoplasmic reticulum causes a proportionally strong calcium release upon stimulation enabling the myocyte to achieve stronger contractility through cross-bridge cycling.


Cardiac glycosides also increase the refractory period of the atrioventriular node, creating a more regular heartbeat.


            Signs and Symptoms:

In children cardiac glycoside ingestion causes severe abdominal pain, diarrhea, nausea and vomiting.  Additional symptoms include lethargy, circumoral flush, dialated pupils, drooling, sweating, shaking, and ashy coloring.

Adults who have ingested plants containing cardiac glycosides frequently exhibit bradycardia, heart block, premature ventricular contractions, and tachydysrhythmia. A common but unusual complaint is xanthopsia (yellow vision).

Rarer symptoms include weakness, dizziness, and drowsiness.

Treatment:

Activated charcoal (1 g/kg)

Fluid Replacement

Electrolyte Correction

Antiemetic

Atropine

Digoxin-specific Fab fragments

Plants:

There are approximately 400 naturally occurring cardiac glycosides.

Foxglove (Digitalis purpurea and D. lanata)

Foxglove

Toxins: digitoxin, digoxin

Sign and Symptoms: Nausea, vomiting, diarrhea, salivation







Oleander (Nerium oleander, Thevetia peruviana)

Toxins: oleandrin, folinerin, digitoxigenin, nerium
Signs and symptoms: Abdominal pain, visual disturbances, hypotension, bradycardia and heart block, tachydysrhythmias, confusion, delirium, lethargy




Lily of the Valley (Convalaria majalis)


Yew (Taxus brevifolia)


Squill (Urginea maritima)


Strophanthus (Strophanthus species)


Wintersweet and ‘Bushman’s Poison’ (Acokantheria species)



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