All 8 species of Thevetia are native to Central America and are now widely cultivated in tropical and subtropical areas globally.
Humans and any animal eating the plants and especially the fruits
Several cardenolides have been identified in yellow oleander, predominantly thevetin A and B. Others include peruvoside, neriine, ruvoside, thevetoxin, and theveridoside. These cardenolides are structurally similar to digitalis cardenolides in foxgloves.
Cardiac glycosides act by inhibiting the cellular membrane sodium/potassium (Na+-K+ ATPase enzyme system) pump. This results in a progressive decrease in electrical conductivity through the heart causing irregular heart activity, and eventually complete block of cardiac activity.
Perennial, branching shrubs to small trees, with simple, linear, alternate, glossy, green leaves and a milky sap. The flowers are produced terminally, and are funnel-shaped, fragrant, showy, with sepals fused basally, and petals ranging from bright yellow to orange or white. Fruits are green, angular drupes that turn red to black when ripe.
The glycosides act directly on the gastrointestinal tract causing hemorrhagic enteritis, abdominal pain, and diarrhea.
Humans suspected of eating yellow oleander should be seen by a physician immediately. Likewise animals eating the plant and showing signs should be treated by a veterinarian. Gastric lavage or vomiting should be induced in dogs and cats as soon as possible. Activated charcoal orally decreases further absorbtion of the cardenolides. Hyperkalemia is a common feature of yellow oleander poisoning, the administration of potassium containing fluids should be done 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.
Sudden onset of weakness, rapid breathing, irregular heart rate, shock-like symptoms may be observed initially. A variety of severe dysrhythmias and conduction disturbances through the myocardium that result in decreased cardiac output, heart block, and death.
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