Cardioactive glycosides

Question 1

Cardioactive glucosides

MCA

Answer 1

• All these glucosides are toxic especially for monogastric animals. In ruminants, they are partially destroyed by bacterial microflora in a paunch (rumen).
• All of them have the same mechanism of action – inhibition of Na/K ATPase and cummulation of Na+ and Ca2+ in heart muscle, which leads to increased contractility, bradycardia and arrhytmias, in severe cases also heart failure.

Question 2

Crownvetch

Answer 2

• Contains cardioactive glucosides – coronilline + hyrcanoside.
• Signs are arrhytmias, and because of the presence of nitrites (3-nitropropionic acid) in
  the plant, methaemoglobinemia occurs too.
  
• Treatment is symptomatic (antiarrhytmics, fluids, minerals and AB balance corrections etc.), but if the dose is not lethal, full recovery is possible, because these agents don’t damage tissues.

Question 3

Oleander

Answer 3

• Cardioactive glucosides oleandrine and neriine, very potent
• Signs are arrhytmias, and because of the presence of nitrites (3-nitropropionic acid) in
  the plant, methaemoglobinemia occurs too.
  
• Treatment is symptomatic (antiarrhytmics, fluids, minerals and AB balance corrections etc.), but if the dose is not lethal, full recovery is possible, because these agents don’t damage tissues.

Question 4

Foxglove (Digitalis ssp.)

Answer 4

• Contains cardioactive glucosides – digoxin, digitoxin and others.
• Digitalis plant is very bitter and strong vomiting follows eating, so there are only a
  few intoxications in wild animals.
• More common is overdose with pure glucosides used for treatment (pills).
• There are antidotes available for this intoxication – specific antibodies against digoxin
  – but they are very expensive and side effects can be harmful too.

Question 5

Sea onion

Answer 5

Scilliroside

• Cardioactive glucosides have enterohepatic cycling
• It has been used since ancient times as a powder made from bulbs
• For animals with vomiting reflex this natural product is quite safe due to content of
emetin, which causes tenacious vomiting and prevents absorption of higher doses of scilliroside to the organism

Mechanism of action:
- all cardioactive glucosides inhibit myocardial form of the enzyme Na/K ATPase, which leads to the cummulation of Na+ inside of muscle cells and their stimulation to prolonged contraction

Clinical signs:

• changes of heart rhythm, which are serious and can lead to death
• nausea, diarrhoea, ataxia, fainting, bradycardia, cyanosis

Treatment:
- emesis, gastric lavage, repetitive doses of activated charcoal, administration of antiarrythmic agents, fluid therapy, oxygen inhalation