Antiarrhythmic Drugs Flashcards
Class 1 antiarrhytmics block which channels?
Fast Na
So class 1 antiarrhytmics block which PHASE of the myocyte AP?
Phase 0
And if you block phase 0, what happens to the conduction velocity and refractory period in myocytes?
decrease CV and increase RP
Which receptors do class 2 antiarrhytmics block?
Beta adrenergic receptors (B-blockers)
Which receptors do class 3 antiarrhytmics block?
K channels
Blocking K channels by class 3 antiarrhytmics does what to the AP?
Prolong it cuz it takes longer to repolarize the membrane
THIS ALSO INCREASES THE REFRACTORY PERIOD. BITCH.
Which channels do class 4 antiarrhytmics block?
Ca++ channels
Procainamide, Quinidine, and disopyramide belong to which class?
Class 1A
Class 1A drugs (DQP) moderately block the Na channel, thus increasing the time it takes for the cell to reach what?
Threshold
Class 1A drugs also block which channel, which prolongs the AP duration and increases the refractory period?
K+ channel
Lidocaine and Mexiletine belong to which class of drugs?
Class 1B
Why are class 1B antiarrhytmics called weak Na channel blockers, even though they bind to open and inactivated Na channel?
It has fast dissociation
This weak blockage of the Na channel by 1B drugs does what to the AP duration and refractory period?
Make them shorter
Lidocaine + Mexiletine = “L”ittle “M”an = little AP
For which conditions are 1B antiarrhytmics good for?
ischemia or any use-dependent problem
What are the 2 class 1C antiarrhytmics?
Propafenone, Flecainide
“P”retty “F”reaky
True or False: Class 1C drugs have no effect on AP duration.
True
True or False: Class 1C drugs have no effect on the speed of phase 0.
FALSE. it decreases it a lot.
True or False: Class 1C drugs have no effect on repolarization.
True!
Since class 2 drugs inhibit the B1 receptors, what does it do to phase 4 depolarization at the nodal tissues?
Decrease it.
Since B1 receptors normally increase Ca current into the cell, what happens to CV and RP with class 2 administration?
CV increases and RP decreases
Amiodarone, dronedarone, sotalol, Dofetilide, and Ibutilide belong to which class of antiarrhytmics?
Class 3
Since you prolong the RP and AP of the myocyte when u give a class 3 (cuz it blocks K channels), what arrhythmia are u putting the pt at risk for?
Torsade de Pontes
True or False: class 3 drugs affect the slope of the phase 0 depolarization in myocytes.
False. They do nothing with it.
Like a wife 20 years into marriage.
Verapamil and Diltiazem belong to which class of antiarrhytmics?
Class 4
WE TALKED ABOUT THIS LAST TEST KINDA YEAH. WOOOOOOOOOOOOOOOO
Which channels do class 4 antiarrhytmics block?
Ca++
True or False: class 4 antiarrhytmics do not affect Na-dependent tissues like purkinje fibers, atrial and ventricular muscle.
True
So where do class 4 antiarrhytmics block Ca++ channels?
SA and AV nodes
Since class 4 antiarrhytmics block the nodes and slow the conduction through them, which type of arrhythmia can they treat?
Re-entry
This is the antiarrhytmic that opens G protein coupled K channels, which inhibit the node coductions, and also inhibits the Ca channel.
Adenosine
