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Oleander
Nerium oleander
Oleander (Nerium oleander) is one of the most acutely toxic ornamental plants for cats. Every part — leaves, flowers, stems, roots, and even dried plant material — contains potent cardenolide cardiac glycosides, primarily oleandrin and neriine. These compounds are similar to digoxin in their mechanism and are toxic in extremely small quantities.
Important Notes
Toxic compounds: oleandrin and neriine (cardenolide cardiac glycosides); all parts are toxic, including dried material and smoke from burning
Mechanism: cardenolides inhibit Na+/K+-ATPase in cardiac muscle, disrupting electrical conduction and causing arrhythmias and heart block
Symptoms: drooling, vomiting, diarrhea, weakness, bradycardia, cardiac arrhythmias, hypotension, collapse; can be rapidly fatal
A single leaf contains enough oleandrin to kill a cat; smoke from burning oleander is also toxic
Any suspected ingestion is a veterinary emergency — do not wait for symptoms
Potentially Toxic Parts
Leaf
Entire Plant
Possible Symptoms Reported in Cats
Irregular heart rhythms (arrhythmias), abnormally slow heart rate (bradycardia) or fast heart rate (tachycardia), and low blood pressure (hypotension)
Cardiac · Within the first 2 hours after exposure,
Drooling (hypersalivation), nausea, vomiting, diarrhea, and abdominal pain
Gastrointestinal · Rapidly, usually within the first 2 hours after exposure,
Lethargy, profound weakness, drowsiness, muscle tremors, seizures, and a lack of consciousness
Gastrointestinal · Manifests quickly, within the first 2 hours as the systemic toxicity progresses15. • Any additional
Difficulty breathing and respiratory changes
Respiratory · Manifests rapidly as the toxicity progresses1. • Any additional
Disclaimer: This summary was compiled from multiple sources and is for informational use only. It is not a diagnosis or treatment plan. Toxicity can vary based on the substance, amount, plant part, and individual cat. If you think your cat may have been exposed to a toxic substance, contact a veterinarian right away.