"Class V" Flashcards
1
Q
What two drugs are in Class V?
A
- Adenosine
- Digitalis/Digoxin
2
Q
What is the mechanism/cardiac effects of Adenosine?
A
- Activation of K+ channels and inhibition of L type Ca2++ channels
- Results in hyper polarization and suppression of Ca2+ dependent AP (nodal tissue)
- Increases AV refractory period
3
Q
What is the mechanism/cardiac effects of Digitalis?
A
- Inhibits Na+/K+ ATPase
- Increases Na+ inside cell inhibiting Na+/Ca2+ antiporter (more calcium in cell improves contractility –> dec. HR)
- Decreased intracellular K+ and increased intracellular Na+ leads to depolarization of membrane –> after polarization at high doses
4
Q
What are the extra cardiac effects of Adenosine?
A
Vasodilation
5
Q
What are the extra cardiac effects of Digitalis?
A
Activates vagal efferents to heart –> slows SA rate and AV conduction (increasing refractory period)
6
Q
Pharmacokinetics of Adenosine?
A
None
7
Q
Pharmacokinetics of Digitalis?
A
Renally excreted!
8
Q
Toxicity of Adenosine?
A
- Flushing, headache
- Rapid arterial hypotension (short lasting w/cessation of drug)
- Methylxanthines (caffeine) competitively antagonize binding of adenosine at the receptor
- AV block (do not use in patients w/2nd or 3rd degree AV block)
9
Q
Toxicity of Digitalis?
A
- Extreme AV block, can cause every type of arrhythmia except atrial fibrillation and flutter!
- not if Hypokalemic, WPW or AV block
- Monitor dose if really impaired, many drug interactions
- GI distress, hyperkalemia, life threatening arrhythmias (increased PR, flattened T waves and decreased QT)
- NOT used often due to TOXICITY!!
10
Q
Therapeutic use of Adenosine?
A
- Conversion of Paroxysmal supraventricular tachycardia
- NOT FOR AFIB or Flutter
11
Q
Therapeutic use of Digitalis?
A
-Used in HF, useful for reducing ventricular rate when being driven by high arterial rate (atrial fibrillation and flutter)
