Tox in The Land: Cardiac Glycosides

Epidemiology (2017 Data)

  • 1689 calls to poison control

  • 559 with moderate or severe toxicity

  • 23 deaths

Digoxin

  • Only commonly used cardiac glycoside in medicine

  • Narrow therapeutic index

  • Renal elimination

  • Uses:

    • Atrial fibrillation

    • Heart failure

Plants

Fox glove

Lily of the valley

Red squill

Oleander

 

Cane Toad

The cane toad excretes cardiac glycosides in its skin along with a psychedelic substance

 
 
 

Mechanism of Action

  • Inhibits Na/K ATPase

  • Increases Vagal Tone —> Decreases conduction through SA/AV nodes

  • Reduces plasma renin concentrations in heart failure —> peripheral vasodilation

 
 
 

Clinical Presentation

Digoxin Effect

  • Downsloping ST depression

  • Flat, inverted or biphasic T wave

  • Short QT

Cardiac Arrhythmias

  • PVCs

  • Bradycardia

  • Heart block

GI toxicity

  • N/V

  • Abdominal pain

  • Anorexia

Neurologic

  • AMS / Lethargy

  • Chromatopsia + Halos around objects

  • Seizures…or was it syncope?

Image from: lifeinthefastlane.com

 

Management

  • Supportive Care

  • Calcium for hyperkalemia?

  • Antidote = Digoxin specific Antibody Fragments (DigiFab)

DigiFab

  • Derived from immunized sheep, used since the 1970s

  • Binds free digoxin and form complexes that are then also removed by the kidney

  • No RCTs done but it has been found to be SAFE unless you happen to have an allergy (rare)

  • Indications

    • Unstable arrhythmia

    • Potassium > 5

    • End organ dysfunction from hypo-perfusion

    • Digoxin level

      • Acute: > 10 ng/mL

      • Chronic: > 4 ng/mL

 
 

Take Home Points

  • Keep cardiac glycoside toxicity on your differential - especially in the setting of Digoxin use, acute hyperkalemia

  • Hypokalemia can increase the potential for toxicity

  • Don’t sweat it if you treated hyperkalemia with calcium in Cardiac Glycoside toxicity but avoid it when able

  • If the patient is critically ill, give 10 vials of DigiFab. Otherwise, there is time to calculate the dose

POST BY: DR. JULIETA LACEY (EM-CC FELLOW)

FACULTY EDITING BY: DR. LAUREN PORTER (MEDICAL TOXICOLOGIST)

References

  1. Gummin DD, Mowry JB, Beuhler MC, Spyker DA, Brooks DE, Dibert KW, et al. 2019 Annual Report of the American Association of Poison Control Centers' National Poison Data System (NPDS): 37th Annual Report. Clin Toxicol. 2020; 58(12):1360. 

  2. Nelson LS, Howland M, Lewin NA, Smith SW, Goldfrank LR, Hoffman RS (eds). Goldfrank's Toxicologic Emergencies, 11e. McGraw Hill; 2019.

  3. Brent J, Burkhart K, Dargan P, Hatten B, Megarbane B, Palmer R, White J (eds). Crit Care Toxicol, 2e. Springer; 2020

  4. Images

    1.  https://en.wikipedia.org/wiki/Lily_of_the_valley#/media/File:Convallaria_majalis_0002.JPG

    2. https://en.wikipedia.org/wiki/File:Urginea_Maritima.jpg

    3. https://upload.wikimedia.org/wikipedia/commons/c/cc/Nerium_oleander_flowers_leaves.jpg

    4. https://upload.wikimedia.org/wikipedia/commons/0/08/Bufo_bufo_sitting-Iric2006.jpg

ToxLauren McCafferty