Digoxin and Cardiac Glycosides (click this, but don't lick this)

1. Cardiac Glycosides
1. Sources: Digitalis purpurea (foxglove; digitalis); Oleander (oleandrin); Yellow Oleander (Thevetin); Red Squill (urginea matitimea, scillaren); Cerebra Manghans (sea mango); Bufo toads (Bufo alvarius and marinus; Colorado river and cane toads; bufodienolides)
2. Mechanisms of action: Block Na/K ATPase, leading to increased intracellular calcium; leads to  vagal activation and cardiac irritability
3. Clinical Effects: Vomiting, Bradycardia, multiple PVCs; hyperkalemia; xanthopsia (seeing yellow halos) 
4. Classic dig toxicity rhythm is BIVENTRICULAR Ventricular TACHYCARDIA (see figure).






5. Patients taking digoxin: dehydration and renal insufficiency leads to toxicity
6. Potassium: K above 5.5 after acute overdose heralds poor prognosis—give digibind, don’t wait for dig level; K may be normal to low in chronic toxicity.
7. AVOID CALCIUM—it can exacerbate intracellular hypercalcemia and lead to cardiac tetany. However, this caveat remains quite controversial in the toxicology literature, with very little real evidence in the peer-reviewed literature. In truth, one suspects that calcium is given inadvertently to dig-toxic patients more often than is recognized-- the use of calcium occurs so frequently as a “reflex” for hyperkalemia.
8. Phenytoin or lidocaine for digoxin-related dysrhythmias—no evidence to support effectiveness.
9. Pacers, atropine, pressurs—may be needed as adjuncts if no digibind available
10. Decontamination/GI elimination with Cholestyramine (esp useful for digitoxin); MDAC
11. Digibind indications: Severe bradycardia, VF/VT; Potassium level >5.5; Serum level at steady state above 10-15 ng/mL; ingestion of >10 mg (adults) or >4 mg (kids)
12. Therapy: Digibind/digifab,

a.     Sheep-derived partial antibody.

b.     Digibind Dose can be calculated :

[Steady state dig level] x weight (in kgs)/ 100

c.     If the digoxin level is unknown, 5 – 10 vials can also be given empirically ( but this typically overestimates the actual dose needed).