Oleander: Beautiful but Deadly to Pets

Nerium oleander is a popular ornamental garden plant due to its beauty and tolerance of poor soil and drought, but unfortunately it’s very toxic to many species of animals.

Dogs, cats, goats, cattle, sheep, camelids, budgerigaries, rabbits and horses are all species that have been affected by oleander. Studies indicate mice, rats and chickens may be more resistant to the cardiac effects of Oleander; however, at higher doses neurological signs may be seen in these animals.

Mechanism of Action   

Oleander contains cardiac glycosides, which inhibit the sodium/potassium ATPase pump, causing hyperkalemia and also increased intracellular calcium leading to early depolarization, cardiac irritability and arrhythmias. 

Last but not least, glycosides decrease sympathetic tone and increase vagal tone, resulting in bradycardia and heart block.

Clinical signs may include:

• Gastrointestinal (vomiting, diarrhea)
• Arrhythmias (bradycardia, tachycardia, ventricular tachycardia, premature ventricular contractions, AV block)
• Blood pressure changes (hypotension or hypertension)
• Neurological signs (lethargy, depression, ataxia, tremors, seizures)
• Dehydration
• Shock

Laboratory Findings

Hyperkalemia is the most common; however, hypoglycemia has been reported as a direct result of the toxins.

Due to potential severity of signs, other changes such as hemoconcentration, prerenal azotemia and electrolyte abnormalities may be seen secondary to the gastrointestinal effects and/or poor perfusion. 

Treating the Asymptomatic Pet

If the pet has presented without symptoms and is a recent exposure (generally three hours or less post exposure), emesis may be considered.  Activated charcoal also should be considered, with repeated doses considered in large exposures.

Monitor the patient in hospital for a minimum of 12 hours. If signs develop, they may last up to three days. Encouraging passage of plant material, particularly in large exposures, is advised. Obtaining baseline electrolytes, glucose, and biochemistry profile is ideal.

Treating the Symptomatic Pet

• Manage vomiting with an antiemetic if needed.
• Administer IV fluids with a balanced electrolyte solution (avoid calcium containing fluids) for rehydration and cardiovascular support.
• Evaluate and address cardiovascular signs—typically hypotension is secondary to arrhythmias. Atropine is appropriate for bradycardia or AV block, lidocaine for tachyarrhythmias.  
• Benzodiazepines may be used for seizures.
• Hyperkalemia may need to be addressed with sodium bicarbonate or insulin/dextrose therapy.
• Specific antagonist: digibind (if available).

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