Cardiac Glycosides Flashcards
Which class of CHF is the following: fatigue, shortness of breath, and coughing on exercise?
Class II
Which class of CHF is the following: comfortable at rest, but exercise minimal?
Class III
Which class of CHF is the following: strenuous exercise limited?
Class I
Which class of CHF is the following: no capacity for exercise, clinical signs at rest?
Class IV
Which drug comes from the following plants: Digitalis lanata & Digitalis purpurea?
Digoxin
What are the 3 components of a cardiac glycoside?
- Lactone
- Steroid
- Sugar
Digitoxin and Digoxin differ based on their “Y” component. What is the “Y” component of Digoxin?
OH
Digitoxin and Digoxin differ based on their “Y” component. What is the “Y” component of Digitoxin?
H
Which of the following has the longer half-life: Digoxin or Digitoxin?
Digitoxin (there is a “t” for “time”)
What 4 conditions can Cardoxin LS be used to treat?
- Heart failure
- Atrial flutter
- Supraventricular fibrillation
- Atrial fibrillation
What are the 3 major effects of cardiac glycosides?
- Positive ionotropic effect
- Negative chronotropic effect
- Negative dromotropic effect
What type of effect is the slowing of the heart rate?
Negative chronotropic effect
What type of effect is the slowing of conduction at the AV node?
Negative dromotropic effect
What type of effect is the increased force and velocity of contraction of the heart?
Positive ionotropic effect
What is the half-life of Digoxin in the dog?
23-39 hours
What is the half-life of Digoxin in the cat?
25-78 hours
What is the half-life of Digoxin in the horse?
13-23 hours
What is the primary mode of elimination of Digoxin?
Renal
What are the deleterious effects of Digoxin on the rhythm of the heart?
- AV block
- Ventricular fibrillation
- Tachycardia
- Atrial arrhythmia
- Ventricular arrhythmia
What are the symptoms of DIgoxin toxicity?
- Extrasystole
- Coupled beats
- GI disturbances (anorexia, vomiting, diarrhea)
Pimobendan is an Inodilator. What is the common name for Pimobendan in veterinary medicine?
Vetmedin
What are the 2 mechanisms of action of Inodilators?
- Calcium sensitization
2. Inhibition of phosphodiesterase III
For Inodilators, how does the calcium sensitizer work?
Tropin I inhibits actin and myosin interaction until calcium binds to Troponin C. Calcium sensitizer increases calcium binding to Troponin C.
For Inodilators, how does the Phosphodiesterase III inhibitor work?
Phosphodiesterase III inhibitor prevents cAMP breakdown and increases PKA (protein kinase A) action, increasing voltage-activated calcium currents.
What are the 5 therapeutic effects of Cardiac Glycosides and Pimobendan?
- Increased cardiac output
- Decreased venous pressure
- Decreased heart rate
- Reduced heart size
- Water loss = reduced body weight
Name 3 other positive ionotropic drugs.
- Dobutamine
- Dopamine
- Amrinone
Dopamine interacts with which receptors on the heart?
D5
Dobutamine is a ____ agonist.
Beta-1
Amrinone is a _____ inhibitor.
Phosphodiesterase III
