11 Antidysrhythmics Upd
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Transcript of 11 Antidysrhythmics Upd
Dysrhythmia Any deviation from the normal rhythm of the
heart
Antidysrhythmics Drugs used for the treatment and prevention of
disturbances in cardiac rhythm
Inside the cardiac cell, there exists a net negative charge relative to the outside of
the cell.
This difference in the electronegative charge.
Results from an uneven distribution of ions (sodium, potassium, calcium) across the cell membrane.
An energy-requiring pump is needed to maintain this uneven distribution of ions.
Sodium-potassium ATPase pump
A change in the distribution of ions causes cardiac cells to become excited.
The movement of ions across the cardiac cell’s membrane results in the propagation of an electrical impulse.
This electrical impulse leads to contraction of the myocardial muscle.
Four Phases The SA node and the Purkinje cells each have
separate action potentials.
System commonly used to classify antidysrhythmic drugs
Class 1 Class Ia Class Ib Class Ic
Class II Class III Class IV Other
Class I Membrane-stabilizing agents Fast sodium channel blockers Divided into Ia, Ib, and Ic agents, according
to effects
Class Imoricizine General Class I agent Has characteristics of all three subclasses Used for symptomatic ventricular and life-
threatening dysrhythmias
Class Iaquinidine, procainamide, disopyramide Block sodium channels Delay repolarization Increase the APD Used for atrial fibrillation, premature atrial
contractions, premature ventricular contractions, ventricular tachycardia, Wolff-Parkinson-White syndrome
Class Ibtocainide, mexiletine, phenytoin, lidocaine Block sodium channels Accelerate repolarization Decrease the APD Used for ventricular dysrhythmias only
(premature ventricular contractions, ventricular tachycardia, ventricular fibrillation)
Class Icencainide, flecainide, propafenone Block sodium channels (more pronounced
effect) Little effect on APD or repolarization Used for severe ventricular dysrhythmias May be used in atrial fibrillation/flutter
Class IIBeta blockers: atenolol, esmolol,
petaprolol, propranolol Reduce or block sympathetic nervous system
stimulation, thus reducing transmission of impulses in the heart’s conduction system
Depress phase 4 depolarization General myocardial depressants for both
supraventricular and ventricular dysrhythmias
Class IIIamiodarone, bretylium, sotalol, ibutilide Increase APD Prolong repolarization in phase 3 Used for dysrhythmias that are difficult to treat Life-threatening ventricular tachycardia or
fibrillation, atrial fibrillation or flutter—resistant to other drugs
Sustained ventricular tachycardia
Class IVverapamil, diltiazem Calcium channel blockers Depress phase 4 depolarization Used for paroxysmal supraventricular
tachycardia; rate control for atrial fibrillation and flutter
Other Antidysrhythmicsdigoxin, adenosine Have properties of several classes and are not
placed into one particular class
Digoxin Cardiac glycoside
Inhibits the sodium-potassium ATPase pump
Positive inotrope—improves the strength of cardiac contraction
Allows more calcium to be available for contraction
Used for CHF and atrial dysrhythmias
Monitor potassium levels, drug levels, and for toxicity
adenosine (Adenocard) Slows conduction through the AV node Used to convert paroxysmal supraventricular
tachycardia to sinus rhythm Very short half-life Only administered as fast IV push May cause asystole for a few seconds Other side effects minimal
ALL antidysrhythmics can cause dysrhythmias!!
Hypersensitivity reactions Nausea Vomiting Diarrhea Dizziness Blurred vision Headache
Obtain a thorough drug and medical history.
Measure baseline BP, P, I & O, and cardiac rhythm.
Measure serum potassium levels before initiating therapy.
Assess for conditions that may be contraindications for use of specific agents.
Assess for potential drug interactions. Instruct patients regarding dosing
schedules and side effects to report to physician.
During therapy, monitor cardiac rhythm, heart rate, BP, general well-being, skin color, temperature, heart and breath sounds.
Assess plasma drug levels as indicated. Monitor for toxic effects.
Instruct patients to take medications as scheduled and not to skip doses or double up for missed doses.
Patients who miss a dose should contact their physician for instructions if a dose is missed.
Instruct patients not to crush or chew any oral sustained-release preparations.
For class I agents, monitor ECG for QT intervals prolonged more than 50%.
IV infusions should be administered with an IV pump.
Patients taking propranolol, digoxin, and other agents should be taught how to take their own radial pulse for 1 full minute, and to notify their physician if the pulse is less than 60 beats/minute before taking the next dose of medication.
Monitor for therapeutic response: Decreased BP in hypertensive patients Decreased edema Regular pulse rate or Pulse rate without major irregularities, or Improved regularity of rhythm