11. Anti Arrhythmic Drugs Class 1 (a,b &c) Flashcards
Based on Vaughan-Williams Classification, what are the 4 classes?
Type 1 - sodium channel blockers 1a intermediate t(recovery) 1b short t(recovery) 1c long t(recovery) Type II - beta antagonists Type III - drugs that prolong action potential Type IV - calcium channel blockers
What are the 3 type 1a drugs?
Quinidine, procainamide and disopyramide
What are the main effects of type 1a?
- Decreases conduction velocity of bundle of his, perkinje fibers, and ventricles
- Prolongs refractory period
- Decreases automaticity of Na - makes threshold more positive
- Block potassium channels
What are the effects of quinidine?
Blocks Na channels, K channel and Ca channel
Antimuscurinic properties - speed conduction through AV node
Blocks alpha-1 –> vasodilation
How is quinidine administered usually? What the IV administration for?
Administered PO
IV administration for atrial or ventricular tachycardia
What is the black box warning for quinidine?
PO: increase mortality in nonlife threatening arrhythmia vs. other AADs; proarrhythmic - QTc prolongation and TdP possible
What are the adverse effects of quinidine? What are toxicity symptoms? What should be monitored?
- TdP, GI upset, immune rxn
- Head ache, dizziness, tinnitus
- EKG, CBC, LFTs
How is procainamide administered?
IV or IM
What is the black box warning for procainamide?
watch for systemic lupus erythematosus and bone marrow depression
What is the main indication for procainamide?
Use for life threatening ventricular arrhythmias only
Does procainamide under go renal metabolism? Hepatic metabolism?
yes and yes
What are the contraindications of procainamide?
SLE, heart block, history of TdP
What should be monitored with procainamide?
EKG, BP, antinuclear antibody (ANA), CBC
What is the usage for disopyramide?
For use in life threatening ventricular arrhythmias only
What is the black box warning for disopyramide?
Can precipitate CHF in pts w/ left ventricular dysfunction
Does disopyramide undergo hepatic and/or renal metabolism?
Yes and yes
What are the contraindications of disopyramide?
Cardiogenic shock, QTc prolongation
What are the adverse effects of disopyramide?
Anticholinergic effects, TdP, CHF, hypotension, anorexia
What should be monitored with disopyramide?
EKG, BUN/sCr, LFTs, blood glucose
What is the Vaughan-Williams Classification of Antiarrrhythmic Drugs?
Categorizing drugs according to their electro physiological effects on their heart (rather than therapeutic target)
What are the three type 1b Antiarrhythmic drugs?
Lidocaine, mexilitine, to asinine, phenytoin
What are the effects of class 1b antiarrhythmic drugs?
- effect tissue w/ frequent rate of depolarization
- decrease automaticity of Na dependent conductive tissues (ex ectopic pacemakers)
- decrease AP duration
- no effect on conduction velocity, but decreases the frequency of firing
- used to terminate arrhythmias that are caused by ectopic pacemakers
What is the primary use of class 1b AADs?
Primarily used to terminate arrhythmias that are caused by ectopic pacemakers
What is the primary use for lidocaine?
Used for ventricular arrhythmias in ACLS
Treatment of choice in acute ischemic ventricular arrhythmias
What is the contraindications of lidocaine?
3rd degree heart block, don’t want to loose communication between atria and ventricles
What are some adverse effect of lidocaine?
Tremor, nausea, slurred speech, seizures
How is mexilitine similar to lidocaine?
It’s an oral lidocaine derivative
What is the black box warning for mexilitine?
Should only be used to treat life threatening ventricular arrhythmias due to its pro-arrhythmic effect
What are some adverse effects of phenytoin?
CNS effects, GI symptoms, gingival hyperplasia, hair growth, hypersensitivity
What are contraindications of phenytoin?
Sinus bradycardia
AV block – phenytoin will worsen AV node block
What will barbiturates do to phenytoin metabolism?
Barbs will induce phenytoin metabolism by inducing CYP450 expression, will want to increase phenytoin dose
What are 3 type 1c AADs?
Flecainide, propafenone, moricizine
What are the effects of class 1c AADs?
- Slowing of conduction velocity
- Has no effect on automaticity of ectopic pacemakers
What are the effect of flecainide?
- decreased conduction velocity
- blocks K channels
- blocks Ca channels
What is flecainide used to treat?
Atrial and ventricular arrhythmias conversion and maintenance of NSR
What is the black box warning for flecainide?
Do not use with post-MI or LVDF
pts, may increase mortality
What are the contraindications of flecainide?
2nd and 3rd degree heart block, or LVDF
What are some adverse effects of flecainide?
Vtach, double vision, HF, dyspnea
What are the effects of propafenone?
- decrease conduction velocity
- block K channels
- block b-AR receptors: depresses triggered activity (DAD, EAD) decreases heart rate
What is the main use of propafenone?
Mainly used IV and PO for atrial arrhythmia conversion and maintenance of NSR
What are the adverse effects of propafenone? What are they mainly caused by?
Mainly caused by b-AR blockage
- exacerbate HF
- bronchospasms
- sinus bradycardia
What is the black box warning with propafenone?
Only for life threatening arrhythmias, has a significant pro-arrhythmic effect
What are some things that should be monitored while on propafenone?
EKG - watching for QTc prolongation
LFTS, CCB, electrolytes
All should be measured every 6 months
What is the CAST trial?
Compared pts with ischemia and potential for SCD due to ventricular arrhythmias on either 1c AADs or placebo
What was the findings of the CAST trial?
Do not give 1c AADs to individuals post-MI or with LVH
