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Class I - Dysrhythmics
Sodium Channel Blockers
Similar in action & structure to local anesthetics.
This decreases conduction velocity in the atria, ventricles and His-Purkinje system.
Three subgroups: A, B, C
In addition to blocking sodium channels
A - delays repolarization
B - accelerate repolarization
C - pronounced prodysrhythmic actions
Class IA dysrhythmic agent
Used to treat supraventricular & ventricular arrhythmias
Slows impulse conduction by blocking sodium channels
Decreases myocardial excitability, conduction velocity, and contractility
Prevents reentry phenomenon
Strongly anticholinergic effects (atropine-like) increases ventricular rate
Quinidine is the oldest and most thoroughly studied of all of the IA drugs.
It is the most frequently used oral antidysrhythmic.
Also has antipyretic and antimalarial properties.
Contraindicated in digitalis toxicity, heart blocks, hypersensitivity to quinidine (or cinchona derivatives)
Common adverse effects: GI symptoms, diarrhea (GI symptoms develop in 33% of patients) cinchonism - ringing in ears, HA, nausea, disturbed vision, vertigo. Can develop after one dose.
Serious adverse effect: Cardiotoxicity, arterial embolism, hypotension with IV use
Nursing: take oral forms with food, telemetry & vital sign monitoring/volumetric flow pump with IV administration. Be aware that quinidine can DOUBLE digoxin levels. Due to its anticholinergic action can intensify the effect of other anticholinergic agents resulting in excessive tachycardia.
Patient teaching: Instruct pt in signs of embolism
Class IB dysrhythmics
Blocks cardiac sodium channels; slow conduction
Used for ventriculardysrhythmias, short term use
Also used as a local anesthetic
Not effective orally; NEVER use preparation with epinepherine intravenously
Most common SE (drug is generally well tolerated:
CV system (dysrhythmias and hypotension)
CNS (dizziness/lightheadedness, fatigue, and drowsiness)
Excessive toxic levels can produce convulsions and respiratory arrest
Monitor ECG continuously and switch to another dysrhythmic as soon as stable.
flecainide (Tambocor) and propafenone (Rythmol): oral agents
Class IC dysrhythmics
Blocks Na+ channels
Delays ventricular repolarization
Decrease conduction significantly
Decreases myocardial contractility; increase HF
Use usually limited because of an increased risk of mortality
Class II Dysrhythmics
Beta Blockers - only selected agents are approved for use as antidysrhythmics
Decreases automaticity; slows the heart
Decreases AV conduction velocity
Decreases myocardial contractility; CO
Prototype agent: propanolol
Contraindicated in sinus bradycardia, pulmonary disease, HF
Class III dysrhythmic
Delay repolarization, prolong QT interval.
Used in life-threatening arrhythmias that have not responded to other drug therapies
examples: recurrent ventricular fibrillation, recurrent unstable ventricular tachycardia
Low dose therapy is common (200mg/day) benefits: LV ejection fraction, exercise tolerance & ventricular arrhythmias in HF pts.
Common adverse effects
CNS - dizziness, tremor, insomnia
Serious Adverse effects:
Pulmonary toxicity (most common)
Exacerbation of the arrhythmia being treated
Photophobia or blurred vision leading to blindness
hyper or hypothyroidism
Pregnancy Category D
Research based practice: amiodarone is commonly used now in treatment of HF, atrial fibrillation, VT, VF not responsive to defibrillation
Inhibits movement of calcium ions across the cardiac and arterial muscle cell membranes
Slows AV conduction
Depresses SA automaticity
Depresses myocardial contractility,
Dilates coronary arteries and peripheral arterioles
Control of ventricular rate in chronic atrial flutter or fibrillation
Prophylactically (with digoxin) for repetitive paroxysmal supraventricular tachycardia
Treatment of supraventricular tachyarrhythmias, not active against ventricular dysrhythmias
AnginaCommon adverse effects: GI - constipation, nausea, CNS
Can cause bradycardia, AV block and HF, hypotension and peripheral edema
Contraindicated in 2nd & 3rd degree heart blocks, hypotension, severe HF
Interactions with digoxin and beta blockers
Elderly patients more sensitive to hypotension
Decreases AV conduction
Decreases SA automaticity
Used to treat SVT only, ineffective in ventricular dysrhythmias
Cardiotoxicity and dysrythmias; increased risk with hypokalemia
GI: anorexia, nausea, vomiting , abdominal pain
CNS: fatigue, visual disturbances
is a nitrate, like nitroglycerin, and is used for treating and preventing angina.
It is not used to treat hypertension.
Is given sublingually or orally.
Because sublingual isosorbide does not relieve chest pain as rapidly as nitroglycerin, isosorbide is limited to treating acute angina in patients intolerant or unresponsive to sublingual nitroglycerin.
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