Toxicity of digitalis:

Sources

• Bufo toads
• Digitalis
• Digoxin
• Foxglove (Digitalis spp.)
• Lily of the valley (Convallaria majalis)
• Milkweeds (Asclepias spp.)
• Oleander (Nerium oleander)
• Rhododendron species

Species

• All species susceptible
• Cats more sensitive than dogs
• Livestock poisoned after consumption of range plants

Kinetics :

Cardiac glycosides are well absorbed orally.

Protein binding varies, with digitoxin being highly protein – bound and digoxin having low protein binding .

 These drugs are metabolized in the liver.

Mechanism of Action:

 Cardiac glycosides interfere with normal functioning of Na + /K + – ATPases, increasing intracellular sodium and extracellular potassium. The final result is an increase in force of contraction, increase in cardiac output, and decrease in heart rate.

Clinical Signs:

 GENERAL

• Weakness

 GASTROINTESTINAL ‘

• Nausea
• Vomiting
• Diarrhea
• Decreased body weight

CARDIOVASCULAR

• Decreased heart rate (sinus bradycardia)
• Second- and third-degree heart block
• Ventricular tachycardia

 CLINICAL PATHOLOGY

• Elevated serum potassium concentration

 TOXICITY

• Due to the differences in concentration of toxic principle, the toxic dose is variable.
• Most animals consume the plants when forage is scarce.

Diagnosis:

• History of exposure to plant or drugs
• Clinical signs
• Chemical confirmation or serum digoxin concentration
• rarely performed in veterinary medicine
• not beneficial in the treatment of an animal with clinical signs.

 Treatment:

 GASTROINTESTINAL DECONTAMINATION

• Activated charcoal
• repeated dosing to prevent enterohepatic recycling
• Cathartic
• Emesis after recent ingestion (dogs and cats)
• Animal may have vomited the material.

SUPPORTIVE AND SYMPTOMATIC THERAPY

• Monitor cardiac function by means of electrocardiogram for small animals.
• Manage bradycardia with atropine.
• Correct hyperkalemia.
• sodium bicarbonate
• glucose and insulin
• increase amount of potassium entering into cells
• possibly monitor serum potassium concentration
• Management of arrhythmias
• lidocaine
• phenytoin
• Oxygen therapy

FOR LARGE ANIMALS

• Treatment may not be practical.
• sudden death
• expense of therapy
• Remove from the source of toxin (pasture).
• Provide alternative feed sources.