Which cardiac glycoside is the primary toxic constituent of Oleander (Nerium oleander) responsible for its cardiotoxic effects?

Explanation

## Oleander Cardiotoxic Glycoside **Key Point:** Oleandrin is the primary cardiac glycoside in Nerium oleander and is structurally and functionally similar to digitalis glycosides (digoxin, digitoxin). ### Mechanism of Cardiotoxicity Oleandrin inhibits the Na^+^/K^+^-ATPase pump in cardiac myocytes, leading to: 1. Increased intracellular Na^+^ and Ca^2+^ 2. Enhanced cardiac contractility (positive inotropic effect) at low doses 3. Arrhythmias and conduction abnormalities at toxic doses 4. Hyperkalemia (due to pump inhibition) ### Clinical Features of Oleander Poisoning - Gastrointestinal: nausea, vomiting, abdominal pain, diarrhea - Cardiac: bradycardia, AV block, ventricular arrhythmias, atrial fibrillation - Neurological: headache, confusion, visual disturbances - Metabolic: hyperkalemia (marker of severity) **Clinical Pearl:** Oleander poisoning mimics digitalis toxicity because oleandrin acts via the same mechanism (Na^+^/K^+^-ATPase inhibition). However, there is no specific antidote for oleandrin; management is supportive, unlike digoxin toxicity where digoxin-specific Fab fragments (DigiFab) can be used. **High-Yield:** All parts of Oleander (leaves, flowers, stems, roots) contain oleandrin and are highly toxic even in small quantities. A single leaf can cause severe poisoning in a child. ## Cardiac Glycosides Comparison | Glycoside | Source | Mechanism | Clinical Use | Oleander Relevance | |-----------|--------|-----------|--------------|-------------------| | Oleandrin | Nerium oleander | Na^+^/K^+^-ATPase inhibitor | None (toxic plant) | **Primary toxin** | | Digoxin | Digitalis lanata | Na^+^/K^+^-ATPase inhibitor | Heart failure, AFib | Therapeutic drug; similar mechanism | | Digitoxin | Digitalis purpurea | Na^+^/K^+^-ATPase inhibitor | Rare (long half-life) | Therapeutic drug; similar mechanism | | Strophanthin | Strophanthus species | Na^+^/K^+^-ATPase inhibitor | Rare (cardiac glycoside) | Different plant source | **Mnemonic:** **OLEO** = **O**leander contains **LEO** (Lethal Evergreen Oleandrin) — emphasizing that all parts are toxic.