Toxic Principle

Oleandrin and neriine are two very potent cardiac glycosides (cardenolides) found in all parts of the plant. Red flowered varieties of oleander appear to be more toxic. Oleander remains toxic when dry. A single leaf can be lethal to a child eating it, although mortality is generally very low in humans. The lethal dose of the green oleander leaves for cattle and horses has been found to be 0.005% of the animal's body weight. The minimum lethal dose of oleander for cattle was found to be 50mg/kg body weight. Horses given 40mg/kg body weight of green oleander leaves via nasogastric tube consistently developed severe gastrointestinal and cardiac toxicosis. Cardiac glycosides that act by inhibiting the cellular membrane sodium-potassium (Na+-K+ ATPase enzyme system) pump with resulting depletion of intracellular potassium and an increase in serum potassium. This results in progressive decrease in electrical conductivity through the heart causing irregular heart activity, and eventual complete block of cardiac activity, and death.

Description

A perennial, evergreen shrub or small tree up to 25 feet tall with whorled, simple, narrow, sharply-pointed, leathery leaves 3-10 inches long with prominent mid-vein. The showy white, pink or red flowers with five or more petals are produced in the spring and summer. Fruit pods contain many seeds, each with a tuft of brown hairs.

Gastrointestinal

Colic, vomiting in some species of animal,

Treatment

Cattle and horses should be given adsorbents such as activated charcoal (2-5gm/kg body weight) orally to prevent further toxin absorbtion. In ruminants known to have eaten oleander, a rumenotomy to remove all traces of the plant from the rumen may be life saving. The cardiac irregularities may be treated using anti-arrhythmic drugs such as potassium chloride, procainamide, lidocaine, dipotassium EDTA, or atropine sulfate). The use of fructose-1,6-diphosphate (FDP) has been shown to effectively reverse hyperkalemia, dysrhythmias and improve cardiac function in dogs experimentally poisoned with oleander. The mechanism of action of FDP is not known but it apparently restores cell membrane Na+-K+ ATPase function. As hyperkalemia is a common feature of oleander poisoning, the use of potassium containing fluids should be used very cautiously, and not at all unless serum potassium levels can be monitored closely. Intravenous fluids containing calcium should not be given as calcium augments the effects of the cardiac glycosides. Poisoned animals should be kept as quiet as possible to avoid further stress on the heart. Inactivation of the absorbed oleander glycosides can be inactivated by using digoxin specific antibodies. These antibodies cross react with oleander glycosides. The digoxin specific antibodies must be given early in the course of poisoning to be effective. ( Reference: Shumaik GM et al. Oleander poisoning: treatment with digoxin-specific Fab antibody fragments. Ann Emerg Med 1988. 17: 732-735.)

Cardiovascular system

Sudden death may be the presenting sign. Cardiac arrhythmias, rapid, weak pulse. Signs of shock including cold extremities, weakness, collapse, and death.

Respiratory System

Difficulty in breathing

Ocular System

Dilated pupils, impaired vision.

Diagnosis

Cardiac arrhythmias, increased serum potassium. Detection of cardiac glycosides in the serum, urine, tissues and stomach contents is possible using high performance liquid chromatography. Oleander glycosides will cross react with digoxin radioimmunoassays.

Special Notes

Livestock are usually poisoned when they are allowed to graze in places where oleander is abundant or when prunings are carelessly thrown into animal pens. Oleander should not be planted in or around livestock enclosures. References