antiarrhythmics Flashcards
class I drugs
sodium channel blockers
block the influx of Na+ into the cell during phase 0 of the action potential
the cells take longer to reach its threshold potential
also reduce the speed of diastolic depolarization (Phase 4)
Class I-a drugs
depress phase 0 depolarization
are more cardiodepressant than class 1B or class 1C drugs
Class I-b drugs
slow phase 0 depolarization
supress ventricular excitability
shorten phase 3 of AP
Class I-c drugs
slow phase 0 of action potential
reduce conductivity
might lengthen refractory periods
Class 1a antiarrhythmics
quinidine
procainamide (pronestyl)
disopryamide (rythmodan)
phenytoin (dilantin)
Quinidine cardiac uses
SVT (e.g. a fib , a flutter, PAT)
ventricular arrhythmias (PVCs)
Quinidine adverse effects
hypotension, syncope
wide QRS, prolong PR, QT intervals
VT or Torsades de pointes
AV heart block
Important when using quinidine
monitor the QT interval
avoid in high degree AV block
potentiates the effect of digoxin
concurrent use with amiodarone can widen the QRS complex
procainamide (pronestyl) cardiac uses
SVT (A fib, PAT)
ventricular arrhythmias (PVC, VT)
procainamide adverse cardiac effects
hypotention
bradycardia, AV heart block
VT, Torsade de pointes, VF, asystole
important points using procainamide
monitor QT interval
avoid in high degree AV block
potentiates the effect of digoxin
conceurrent use with amiodarone can cause procainamide toxicity
concurrent use with beta blockers potentiates the cardiac depressant effect
d/c IV procainamide if one of the four following
- the arrhythmia is supressed
QRS widens by 50% of its original width
hypotension
a total of 500 mg administered
e.g. of Class 1b drugs
lidocaine
tocainide (tonocard)
mexiletine (mexitil)
lidocaine’s half life is ____, so to maintain serum levels and ____
short
IV bolus after maintenance infusion
NEVE administer lidocaine to control
symptomatic IVR,
it would suppress the heart’s only pacemaker
Tocainide use cautiously with
beta blockers
in the presence of heart failure
avoid use of tocainide with
known sensitivity to local amide-type anesthetics (e.g. lidocaine)
class Ic drugs (e.g.)
flecainide (tambocor)
propafenone (rythmol)
moricizine( ethmozine)
flecainide should be avoided
following recent MI
high degree AV blocks, chronic A. Fib
known heart failure
concurrent use of flecainide with ___ may potentiate the action of both drugs
beta blockers
Propafenone (rythmol) avoid use with
AV blockers, BBBB
hypotension, heart failutre
concurrent use with quinidine cans______
slow the metabolism of propafenone
propafenone may potentiate the action of
beta blockers
warfarin
propafenone with permanent pacemaker
reassess thresholds
CLASS II (beta-blockers, -lol)
impede catecholamine stimulation
lower BP, HR, speed of conduction, contractility
2 common use of beta blockers
HTN
long term management of agina pectoris
side effects of beta blockers
dyspnea, cough bronchospasm
heart failure, palpitations, hypotension, syncope
AV heart block, bradycardia, sinus arrest
beta blockers use caution with
asthmatics and patents with bronchospastic disease
beta blockers mask signs of
hypoglycaemia, use cautiously in diabetics
atenolol concurrent use with ____ increase the risk of heart failure, bradycardia, heart block
calcium channel blockers
to manage HTN, atenolol is often use with _____
thiazide diuretic therapy
metoprolol can enhance the effects of class __ antiarrhythmics
1a
avoid use of sotalol with
prolong QT interval
hypokalemia, potassium depleting diuretics
class III antiarrhythmics
potassium channel blockers affect repolarization
lengthen the AP
e.g. amiodarone
cardiac use of amiodarone
SVT, tachycardia secondary to Wolff-Parkinson-White syndrome
life-threatening arrhythmias (VT, VF)
oral amiodarone used with IV administration b/c
oral amiodarone has a long half life of 45 days
adverse effects of amiodarone
can increase resistance to cardioversion
pulmonary toxicity
amiodarone interacts with ___
monitor
warfarin
PT and INR
amiodarone is contraindicated in patients with
acute hepatitis
_____ commonly occur with use of amiodarone
photosensitivity and corneal deposits
class IV antiarrhythmics
calcium channel blockers
depress phases 2 and 3 of the action potential
can interrupt circus movements in tachy caused by AV nodal reentry
e.g. verapamil
diltiazem
avoid calcium channel blockers with
beta blockers
contraindicated in acute MI, advanced HF, pulmonary edema, hypotension, cardiogenic shock, AV block
adenosine
produces transient AV node block and interrupts reentry pathways
very short half life (10 second)
most patients develop a short-lived (<10 seconds) sinister rhythm e.g. asystole or 3 av block
atropine
sympathetic nervous sytem to gaind control
epinephrine
avoid use
patient with sulfite allergies
incompatible with alkaline solution (e.g. sodium bicarb)
digoxin strengthens
myocardial contractility
d/c digoxin ___ pre cardioversion
48 hours
avoid use of digoxin in
wolff-parkinson -white syndrome, AV block, VT
magnesium sulfate ___ muscle cell excitability
decreases
use magnesium sulfate cautiously with
renal disease
______ conteracts magnesium toxicity
calcium
