Anti arrhythmic drugs

Question 1

how are anti-arrhythmic drugs classified?

Answer 1

Vaughan Williams classification system based on mechanism of action

Question 2

order of effectiveness of class1 antiarrhythmics?

Answer 2

1c>1a>1b

Question 3

which class 1 drug is only suitable for ventricular arrhythmias?

Answer 3

1b

Question 4

how do class 1a antiarrhythmics work?

Answer 4

slow phase 0 depolarisation
prolong action potential and slow conduction

Question 5

how do class 1b antiarrhythmics work?

Answer 5

shorten phase 3 repolarisation
decrease length of action potential

Question 6

how do class 1c antiarrhythmics work?

Answer 6

slow phase 0 depolarisation and conduction

Question 7

how do class 2 (beta blockers) work?

Answer 7

block catecholamine action
reduce spontaneous depolarization and conduction

Question 8

how do class 3 (K+ channel blockers) work?

Answer 8

prolong phase 3 repolarisation without affecting phase 0
prolong action potential

Question 9

how do class 4 ( Ca2+ blockers) antiarrhythmics work?

Answer 9

slow phase 4 spontaneous depolarisation
slow conductance in AV node

Question 10

what is rate(use)-dependent channel blockade?

Answer 10

preferentially block in depolarised tissues
enhanced efficacy in rapidly depolarising tissue vs normal sinus rate

Question 11

type of proarrythmia?

Answer 11

Torsades de pointes
associated with class 3 and 1a and drug induced long QT syndrome