• Decreased conduction velocity in cardiac tissues
• suppression of automaticity, which decreases the likelihood of ectopic foci
• Increased recovery time (repolarization or refractory period)

1. 1A: slows cocndution and prolongs repolarization
2. 1B: slows conduction and shorten repolarization
3. 1C: prolongs conduction with little to no effect on repolarization

• Lidocaine slows conduction velocity and decreases action potential amplitude. 
• Onset of action (IV) is rapid.
• 1/3 of lidocaine reaches the general circulation
• A bolus of lidocaine is short lived

disopyramide phosphate

(Norpace, Napamide)

• Sodium 1A Channel Blocker
• Prevention and suppression of unifocal and multifocal premature ventricular contractions (PVCs)
• For ventricular dysrhythmias
• May cause anticholinergic symptoms
• Serum therapeutic level: 3-8 mcg/ml
• Pregancy Category C

procainamide HCL

(Procanbid, Pronestyl)

• Sodium 1A Channel Blocker
• Controls dysrhythmias (PVCs), ventricular tachycardia
• depresses myocardial excitability by slowing down condutivity of cardiac tissue
• Pregnancy category C

quinidine sulfate, quinidine polygalacturonate, quinidine gluconate

(Quinidex, cardioquin)

• Sodium 1A channel blocker
• For atrial, ventricular and supraventricular dysrhythmias
• Common side effects Nausea, vomiting, diarrhea, abdominal pain or cramps
• if given with digoxin can increase digoxin concentrations
• Serum therapeutic level 2-4 mcg/ml
• Pregnancy category C

lidocaine

(Xylocaine)

• Sodium 1B channel blocker
• for acute ventricular dysrhythmias follwoing MI and cardiac surgery
• serum therapeutic range 1.5-6 mcg/ml
• Pregnancy category B

mexiletine HCL

(Mexitil)

• Sodium 1B Channel Blockers
• Analogue of lidocaine
• Treatment for acute and chronic ventricular dyshrythmias
• Take iwth food to decrease GI distress
• Common side effects: nausea, vomiting, hearburn, tremor, dizziness, nervousness, lightheadedness
• Serum therapeutic range 0.5-2 mcg/ml
• Pregnancy category C

• Sodium 1B channel blocker
• For ventricular dysrhythmias, especially PVCs
• similiar to lidocaine except in oral form
• Serum therapeutic level 4-10 mcg/ml
• Pregnancy category C

flecainide

(Tambocor)

• sodium 1C channel blocker
• For life threatening ventricular dysrhythmias , prevention of paroxysmal supraventricular tachycardia (PSVT) and paroxysmal atrial fibrilation or flutter (PAF)
• Avoid use in cardiogenic shock, secon-or third- degree heart block or right bulndle branch block
• Pregnancy category C

propafenon HCL

(Rythmol)

• Sodium 1C channel blocker
• Treatment of life-threatening ventricular dysrhythmias
• Avoid use of cardiogenic shock, uncontrolled HF, heart block, severe hypotension, bradycardia nad bronchospasms occur
• Pregnancy category C

• Can cause cardiovascular depression, bradycardia, hypotension, seizures, blurred vision and double vision.
• Less serious side effects may indclude dizziness, light-headedness and confusiong
• Use with caution in clients iwth liver disorder and heart failure
• Mexiletine and tocainide are contrainindicated for use in clients with cardiogenic shock or in those with second or third degree heart block.

• All antidysrhythmic drugs are potentially prodysrhythmic.
• This is becuase of both the pharmacologic activity of the drug on the heart and the inherently unpredictable activiy of a disease heart, with or without the use of drugs.
• In some cases life threatening ventricular dysrhythmias can result from appropriate and skillful attempts at drug therapy to treat clients with heart disease. 
• Antidysrhythmic drug theraphy is often initiaded during continuous cardiac monitoring of the client's heart rhythm in a hospital setting.