Drug Class: Cardiac Glycosides

Question 1

Example of cardiac glycosides

Answer 1

Digoxin

Question 2

Mode of action of cardiac glycoside

Answer 2

• Inhibits Na+/K+ ATPase

- Positive inotrope- ↑ Ca2+ in myocytes 
- Increase vagal tone (slows SA/VA node conduction)
- Reduced refractory period in myocardium

Question 3

Side effects of cardiac glycosides

Answer 3

• Nausea
• Confusion
• Arrhythmias- VT &VF
• Tachycardia
• Bradycardia
• Xanthopsia (yellow halos around objects)
• Reverse tick sign in lateral leads (V4, V5, V6)

Question 4

What conditions are cardiac glycosides used for?

Answer 4

• Heart failure
• A Fib
• Atrial flutter
• SVT

Used for difficult AFib or Atrial flutter in combination with Beta Blocker/CCB

Question 5

Contraindications of cardiac glycoside

Answer 5

• Narrow therapeutic index
• Long half-life
  
  • Excretion proportional to GFR
  • Caution in renal impairment (elderly)
• Monitor K+ levels-> low K+= digotoxicity

Question 6

What to do if Digoxin toxicity?

Answer 6

In digoxin toxicity:

• Stop drug but long half-life
  
  • Give DIGIBIND- immune antibody

Question 7

What is the mode of action of adenosine?

Answer 7

binds to adenosine receptors in AV node

-> slows conduction through AV node

Question 8

Side effects of adenosine

Answer 8

• May cause asystole for a few seconds

* Sense of impending doom

Question 9

How is adenosine used to diagnose Atrial flutter or atrial fibrillation

Answer 9

If given in SVT with rapid narrow complex tachycardia

- Block AV node= flutter wave – see underlying atrial activity by blocking ventricular activity

Question 10

Contraindications of adenosine

Answer 10

• Short half life
• Administered as fast IV push
• Avoid in asthma patients= BRONCHOSPASM