Antiarrhythmic Drugs Flashcards
What drug class does Quinidine belong to?
Class IA
Quinidine: ______ used any more
Rarely
What is the clinical use of Quinidine?
Effective in supraventricular tachycardias WPW, and suppress premature ventricular contractions
What is the effect of Quinidine administered with afib and flutter?
Increases threshold for atrial fibrillation/flutter (can convert or slow the ventricular response)
What is Quinidine derived from?
Derived from quinine
What is the metabolism of Quinidine?
Hydroxylated in the liver/excreted in urine
When does Quinidine accumulate?
Accumulates with liver/renal insufficiency, sensitive to hepatic enzyme activity
What is the side effect of Quinidine?
Low therapeutic threshold: heart block, hypotension, pro-arrhythmic as plasma levels increase d/t prolongation of P-R, QRS complex, & QTc interval on ECG
Who is Quinidine contraindicated with?
Patients w/preexisting prolongation of the QTc interval or AV heart blocks should not be tx w/ quinidine
What are other properties of Quinidine?
Has anticholinergic/sympathomimetic effects (pts exhibit increased HR – digoxin often given before quinidine tx started)
What are the adverse effects of Quinidine?
Prone to allergic reactions and thrombocytopenia
What can Quinidine be added with? What does it cause?
Possess alpha-adrenergic blocking effects therefore additive with other vasodilating agents (hypotension d/t vasodilation)
What does Quinidine accentuate?
Accentuates the effects of neuromuscular blocking agents
What is chinchonisms?
Quinidine
- Unique side effect symptomology called cinchonism: tinnitus, visual-hearing-GI issues
What class does procrainamide belong to?
Class IA
What is the clinical use of Procainamide?
- Used for tx of ventricular tachyarrhythmias (less effective w/atrial)
- Not used as much any more
- Used in Afib to reduce ventricular irritability
What is Procainamide an anaglogue to?
Analogue of procaine
What are the effects of Procainamide?
Prolongs QRS duration, less QTc prolongation than quinidine
What can Procainamide precipitate?
May precipitate ventricular arrhythmias w/excessive plasma concentrations
What can be a side effect of Procainamide?
- Causes hypotension
- Due to direct myocardial depressant effects - exaggerated with hyperkalemia
When can asytole or VF occur with Procainamide?
Asystole or VF when given with heart block
What is the metabolism of Procainamide?
- Undergoes hepatic metabolism & renal excretion
- hepatic acetylation metabolite NAPA (N-acetyl procainamide) which is renally excreted
Define NAPA.
cardioactive, contributes to antiarrhythmic effect
What dose is needed in renal dysfunction?
Procainamide
What is N-acetyltransferase enzyme important in?
acetylation of procainamide (slow v fast acetylators)
What syndrome can occur with chronic administration of Procainamide?
Lupus-like syndrome with chronic administration (serositis, arthritis, pleurisy, pericarditis
What are other medications in the Class IA?
Disopyramide/Moricizine
What is the use of Disopyramide?
Used for atrial and ventricular tachyarrhythmias
What is the form of Disopyramide?
Oral form only
What are side effects of Disopyramide?
- Significant myocardial depressant and precipitate CHF
- Prolongation of QT and risk of paroxysmal ventricular arrhythmias
What is the clinical use of Moricizine?
Reserved for life threatening ventricular arrhythmias when cannot use others
When is Moricizine not effective?
Not effective in atrial arrhythmias
What are the effects of Moricizine?
Proarrhythmic and may increase BP and HR
What is the clinical use of Lidocaine?
- Primarily used for suppression of ventricular arrhythmias especially re-entry ventricular arrhythmias (PVCs & V-tach)
What class does Lidocaine belong to?
(Class IB)
Why is Lidocaine (Class IB) recommended drug of choice?
More rapid acting than quinidine or procainamide, greater therapeutic index, reduced side effect profile
When is Lidocaine (Class IA) not effective?
Not effective in atrial tachyarrhythmias
What is the metabolism of Lidocaine (Class IA)?
Metabolized in liver
Lidocaine (Class IA): Decreased CO or hepatic blood flow requires ________
decrease dose
What can effect metabolism of Lidocaine (Class IA)?
- Affected by P450 enzyme inhibition as caused by propranolol or cimetidine
- Concomitant administration with cimetidine & propranolol can lead to decreased hepatic clearance of lidocaine
What is the inital dose of Lidocaine (Class IA)?
Initial dose: 2mg/kg followed by infusion 1-4 mg/min achieves therapeutic plasma concentration 1-5 mcg/ml
What effect does lidocaine have at the AP?
- Decreases the rate of spontaneous Phase 4 depolarization in ventricular cells
- Affects K+ permeability during phase 4 of ventricular AP and prevents spontaneous depolarization
What are the effects of Lidocaine (Class IA) toxicity?
peripheral dilation and cardiac depression with bradycardia, prolonged PR and widened QRS
What is the plasma concetration with Lidocaine (Class IA) toxicity?
Lidocaine toxicity (plasma concentration 5-10 mcg/ml)
When are effects of Lidocaine (Class IA) toxicity seen?
CNS symptoms start appearing at plasma 5 mcg/ml; Seizure threshold decreases with hyperkalemia, acidosis, hypoxemia (review LAST s/s)
What is the clinical indications of Phenytoin?
- Effective in suppression of ventricular arrhythmias asso/w digitalis toxicity
- Can be useful in tx of VT or Torsades asso w/ prolonged QTc interval on ECG
What is the MOA of Phenytoin?
- affects automaticity and velocity of conduction of cardiac impulses (similar to lidocaine)
- may depress SA node
Why should caution be taken when administering volatile anesthetics and Phenytoin?
may depress SA node (caution if coadministering with volatile anesthetics)
What is the dose of Phenytoin?
Dose 100 mg q 5 min until arrythmia controlled (max 1000 mg)
What can Phenytoin be non effective in?
Not effective for atrial tachyarrhythmias
What is the IV administration of Phenytoin?
Given slow IV in large peripheral vein diluted in normal saline
What is the metabolism of Phenytoin?
Hepatic metabolism- impaired hepatic function can lead to higher than normal blood levels
What id the elimination half time of Phenytoin?
24 hrs
What lowers blood levels of Phenytoin?
- Blood levels lowered by barbiturates
What raises Phenytoin levels?
warfarin, phenylbutazone, isoniazid inhibit metabolism of phenytoin & increase blood levels
What are the side effects of phenytoin toxicity?
CNS disturbances (cerebellar): ataxia, nystagmus, vertigo, slurred speech, sedation, mental confusion
What is the class of Flecainide?
(Class IC)
What is the analogue of Flecainide (Class IC)?
Fluorinated local anesthetic analogue of procainamide
What is the indication of Flecainide (Class IC)?
Increased incidence of sudden death (pro-arrhythmic); use reserved for tx of life-threatening arrhythmias
What is Flecainide (Class IC) effective in supressing?
Effective in suppressing PVCs, Vtach, atrial tachyarrhythmias, & re-entry arrhythmias (i.e.,WPW)
What are the properties of Flecainide (Class IC)?
Negative inotropic effect and proarrhythmic (esp in presence of decreased LV function)
What can Flecainide (Class IC) increase? Why?
Competes w/metabolic pathways used by other drugs – may increase plasma concentration of digoxin & propranolol
Coadministration with amiodarone will ______ flecainide concentration
double
What are side effects of Flecainide (Class IC)?
prolongs QRS complex and PR interval; not administered w/ 2nd or 3rd AVBs
What is the most common non cardiac effect?
blurred vision
What is the drug class of Propafenone?
Propafenone (Class IC)
What are the clinical uses of Propafenone (Class IC)?
Possesses weak β-adrenergic blocking & calcium blocking effects
What are the proarrhythmic properties of Propafenone (Class IC)?
Proarrhythmic esp in pts w/poor LV function & sustained v-tach
What properies are seen with Propafenone (Class IC)?
Depresses myocardium & may cause SA node slowing, AVB, & BBB
What can increase plasma concentration to Propafenone (Class IC)?
Increases plasma concentration of warfarin
What are the indications for β-adrenergic Antagonists (Class II)?
Effective for tx of cardiac arrhythmias r/t enhanced SNS (periop stress, thyrotoxicosis, pheochromocytoma)
What are propranolol and esmolol effective in treating?
controlling ventricular rate with Afib and Aflutter
What can effectively treat multifocal atrial tach?
Esmolol & metoprolol effective for multifocal atrial tach (amiodarone better)
Which β-adrenergic Antagonists (Class II) are associated with sudden death post MI?
Acebutolol, propranolol and metoprolol approved to prevent sudden death post MI
What is a specific indication of Propranolol?
- Propranolol to emergently suppress ventricular arrhythmias: 1 mg/min (3-6 mg)
- Effective blockade is reflected in HR 55-60
What is the MOA of β-adrenergic Antagonists (Class II)?
Block the cardiac β-receptors to affects of SNS stimulation & circulating catecholamines
What affect does β-adrenergic Antagonists (Class II) have on the heart?
- Decreasing rate of spontaneous phase 4 depolarization and SA node discharge
- Slow impulses through AV node (prolonged PR interval)
- Direct cardiac depressant effects as well as through beta blockade
What does β-adrenergic Antagonists (Class II) cause?
**Membrane stabilization by altering the membrane electrical activity
What are side effects of β-adrenergic Antagonists (Class II)?
bradycardia, hypotension, myocardial depression, bronchospasm, drug fever, mental depression, fatigue
What can β-adrenergic Antagonists (Class II) accentuate?
Can accentuate CHF
What is a contraindication of β-adrenergic Antagonists (Class II)?
Contraindicated in preexisting AV block
How does upregulation of β-adrenergic Antagonists (Class II) occurs
Upregulation of β-receptors occurs w/chronic administration of β-antagonists
What does abrupt d/c of β-adrenergic Antagonists (Class II) lead to?
May lead to SVT
