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

  • 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.