Anti-arrhythmic drugs Flashcards
What is a class 1 anti-arrhythmic drug?
A drug that modifies the action potential by acting on the voltage-activated sodium channels
How does flecanide work?
Inhibits conduction through His-purkinje system
Suppresses ventricular ectopic beats
What subset of class 1 is flecanide?
Class 1 - C
In which conditions is flecanide used?
Paroxysmal AF
Ventricular ectopic beats
What subset of class 1 is quinidine?
Class 1 - A
How do class 1 A drugs work?
Increase the length of the action potential
Increase refractory period
Block sodium channels when they are in the “open” or “active” state
They have some muscarinic effects
In what conditions is quinidine used?
AF
Give with digoxin to slow AV conduction and prevent VT
How do class 1 B drugs work?
Block sodium channels in “refractory” state
Shortens action potential
Lengthens refractory period
Give an example of a class 1 B drug.
Lignocaine
Which conditions is lignocaine used in?
Useful in cells affected by ischemia - used in patients post MI, particularly effective in prevention of arrhythmias such as VT
What type of drugs are class 2 anti-arrhythmic drugs?
Beta blockers
How do class 2 anti-arrhythmic drugs work?
Counteract elevated sympathetic activity
Increase refractory period of SA node
Decrease SA & AV activity
What arrhythmias are beta blockers used to treat?
Used in the prevention of paroxysmal attacks of AF
Give two examples of class 3 drugs.
Amiodarone
Sotalol
How do class 3 anti-arrhythmics work?
They substantially prolong the action potential by blocking voltage-activated potassium channels
This also increases refractory period
What effect does increased action potential and refractory period have?
Interrupts re-entrant tachycardia
Suppresses ectopic activity
What is amiodarone used to treat?
VT & SVTs
Tachycardia associated with WPW
What is sotalol used to treat?
It can prevent short runs of VT
Used in paroxysmal SVTs e.g. AF
What side effects can amiodarone cause?
Blue/slate grey skin
Thyroid abnormalities
Pulmonary fibrosis
What type of drugs are class 4 anti-arrhythmic drugs?
Calcium channel antagonists
Which class 4 anti-arrhythmic is the drug of choice and why?
Verapamil - selective for cardiac calcium channels
How do class 4 anti-arrhythmic drugs work?
Slows SA & AV conduction
In which condition is the use of verapamil contraindicated?
In conjuction with beta-blockers
In Wolf-Parkinson-White syndrome
Which drug is also important in the treatment of arrhythmias that does not belong to any class?
Adenosine
