Drugs Flashcards
What phase of the action potential does class Ia effect?
Prevents sodium influx in phase 0, and block potassium currents to lengthen the action potential.
What are the Class Ia drugs?
Quinidine - Cadioquin
Procainamide - Pronestyl
Disopyramide - Norpace
How does Class Ia drugs work?
Blocks Na channels and slows conduction velocity, decreasing the speed of depolarization.
Which class I slows the rate of the action potential rise and prolong ventricular effective refractory period?
IA
What is the pharmacokinetic characteristic of Quinidine?
Rapid oral absorption
What is the mechanism of Quinidine anti arrhythmic activity?
Active sodium channel blockade
Depression of conduction velocity
Reduced excitability
Is Quinidine effective in suppressing SVT/WPW?
True
What is the principal ion for the SA and AV node?
Calcium
What Drugs are Class Ib?
Lidocaine
Tocainide
Mexiletine
Phenytoin - Dilantin
What is a short acting B-adrenergic receptor agonist?
Esmolol (Brevilock)
What drug can delay after depolarizations?
digoxin toxicity
What receptors does Isoproterenol stimulate?
Beta 1&2.
Increase HR, enhanced conduction time through AV node. Causes arterial vasodilitation
What are Ic Drugs?
Flecainide
What effects can Quinidine have
Prolong QRS
Increase pacing and defib thresholds
Improve AVN conduction
What actions does Procainamide have?
Prolong P-R, QRS, QT interval
Increase pacing threshold
Choice for AFIB conducting down BT
What are Disopyramide actions
Prolong the QRS and QT interval
Negative Inotrope
What needs to be monitored when giving a Class 1a?
Watch QT interval want it to be <500ms
May cause EADs
What is the first line drug in the treatment of VT?
Lidocaine
What is the action of Mexiletine
Shortens action potential duration
Increases the ERP of the HIS outline system
Treat VT
What are the primary actions of Phenytoin?
Shortens QT
Used in children for LQTS when BB fail
DOC in dig toxicity by maintaining AV node conduction and inhibiting DADs
What are the primary actions of Tocainide
PO form of lidocaine
Shortens action potential
Deceased ERP of HiS purkinje system
What are the 1C drugs?
Moricizine - Ethmozine
FlecInide - Tambocor
Propafenone - Rhythmol
How do class Ic drugs work?
Block sodium fast current
Depresses depolarization without changing action potential duration.
What does 1c drugs treat?
SVT
Widens the QRS with inhibition of HIS
Depress upstroke of phase 0
What does flecainide treat?
VT and SVT including WPW, AFIB, and AFlutter
Not for pts with structural heart disease.
Increase pacing thresholds and DFT
Decreases conduction velocity therefore prolongs P-R and QRS
What does Moricizine treat?
-Increase a regrade and retrograde refractory in re entrant limbs of WPW
-Slows retrograde conduction AVNRT
-Exercise stress when initiated Tx
Not for patients with structural heart disease?
What doe Propafenone treat?
Used for VT, SVT, AF, AFL, WPW Prolongs P-R and QRS with no effect on QT Slows AV conduction Mild BB and CAB effects Increase pacing thresholds
Considerations for Ic drugs
Arrhythmia a may be provoked with increase heart rate
Exercise stress test
Not for pts with underlying heart dx
What are Class II drugs?
Beta Blockers
Block effects of catacholamines
Decrease SA and AV conduction
Increase refractory of AVN
What are the Class II drugs?
propranolol - Inderal
Sotalol - Betapace
Cartelol
Carvedolol
What are the class III drugs?
Amiodarone Sotalol Bretylium Ibutilide Dofetilide - Tikosyn
How do Class III drugs work?
Prolongs action potential Blocks potassium currents Prolongs refractory pd Prolongs QT interval Little effect on conduction velocity
How does Amiodarone work
- Increases ERP of tissue
- Prolongs AP duration
- Slows conduction through AVN b/c beta receptor inhibition
- calcium agonist
- increase pacing thresholds and DFT
- Tx VT and VF and maintaining SR
How does Sotalol work?
Used to treat VT, VF, AFIB, AFL
Prolongs refractory pd in atrial, AVN, BT and ventricle
Increase pacing thresholds
How does Ibutilide work?
QT and QTc prolongation
Prolongs repolarization
Pharmacological cardio version
Can cause torsades
How does Tikosyn work?
Delays repolarization by blocking inward k rectifiers
Prolongs QT and QTc without effecting Ca currents
Decrease DFT
Mild negative ionotrope
Hospital loading for 72hrs to monitor QT
What are Class IV drugs?
Calcium channel blockers
Vasodilator and decrease PVR
Negative Inotrope
Slows SA and AVN conduction
What are the class IV drugs?
Nifedipine Verapamil Diltiazem Amyloid pine Bepridil
How does verapamil work?
Used for SVT NOT WPW or LGL Increases AVN ERP and AV block Increase pacing threshold Tx for exercise induced VT/RVOT Tx HF post MI Relaxes arteries throughout system
What are Afterdepolarizations?
Early occur in phase 2 or 3
Late occur in phase 4
If early enough can initiate an action potential
What is EAD
Early afterdwpolarizatjon
Proposed mechanism for Torsades
Hypomagnesemia, hypokalemia
What increases EADs?
Increase sympathetic tone Hypoxia Hypokalemia Bradycardia Sotalol, quinidine n-acetylprocainamide
What causes DADs?
Dig toxicity Tachycardia Hypokalemia Hypercalcemia Catacholamines
What drugs increase DFTs?
Ecainide Flecainide Lidocaine Amiodarone Propafenone Mexiletine Moricizine
WhT drugs decrease DFTs?
Ami
Sotalol
Procainamide
What effect does diltiazem have on the AVN?
Slows conduction by blocking Ca channels
Cardiac cells resting transmembrane potential is?
-90mV
Which areas of the heart exhibit the type of action potential known as the “slow response” type?
SA and AVN
A 33yo woman with paroxysmal AFIB has an evaluation that reveals normal physician exam, normal ECG and echo. The most reasonable anti arrhythmic agent to start her on as an outpatient?
Flecainide
