Antiarrhythmics Flashcards
What are non-VW agents used in arrhythmias?
Adenosine and digoxin
Describe the Vaughan Williams classification of antiarrhythmics
Class I = Na channel blockers Class II = Beta blockers Class III = K channel blockers Class IV = CCBs Class V = variable mechanisms (adenosine, digoxin)
Class IA antiarrhythmics
Procainamide
Quinidine
Disopyramide
(Na channel blockers)
Class IB antiarrhythmics
Lidocaine Mexilitine (Na channel blockers)
Class IC antiarrhythmics
Flecainide Propafenone (Na channel blockers)
Which Class I antiarrhythmics should NOT be used after IC?
IA
Effects of Class IA drugs
- Reduces AP duration and ventricular refractoriness
- Increases repolarization
Effects of Class IB drugs
Shortens AP duration, ventricular refractoriness and repolarization
Effects of Class IC drugs
Markedly slows depolarization without affecting repolarization
Procainamide (class, indications, key features)
- Class IA Na channel blocker
- Stable monomorphic VT, VT w/accessory pathway, non-VT/VF arrest
- IV only!
Procainamide ADRs
- Peripheral vasodilation
- Hypotension
- Reflex tachy
- Arrest
How is procainamide metabolized? What is its half life?
- CYP2D6
- 2.5 to 8 hours (NAPA metabolite 5-9 hours)
How is procainamide dosed in renal and hepatic impairments?
- Lower loading dose in renal
- Cut all doses 50% in hepatic
What drugs interact with procainamide?
- Tricyclics
- SSRIs
- Opioids
Procainamide serious adverse events
- Heart block, widening QRS, Torsades
- Hepatotoxicity
- Drug induced lupus
Disopyramide (class, indications, key features)
- Class IA Na channel blocker
- Stable monomorphic VT, AF conversion
- Used as an alternative to procainamide
- A/w cardiogenic shock
How is disopyramide metabolized? What is its half life?
- CYP3A4, significant 1st pass
- Half life 4-10 hours
How is disopyramide dosed?
Weight based
When is disopyramide adjusted in renal impairment?
CrCl less than 40 mL/min
Disopyramide serious adverse events
- Torsades, HF, hypotension
- Xerostomia
- Urinary hesitancy
- Constipation
- Rash
Disopyramide contraindications
- AV block
- QT prolongation
- Cardiogenic shock
Disopyramide has significant ____ effects, so it should be avoided in patients with _____
- Anticholinergic
- Avoid in glaucoma and myasthenia gravis
Quinidine (class, indications, key features)
- Class IA Na channel blocker
- Maintenance of sinus rhythm when LV function is preserved
- NOT used for ventricular arrhythmias
How is quinidine metabolized?
- CYP3A4
- Metabolite has antiarrhythmic effects that need to be accounted for
Quinidine serious adverse events
- Arrhythmias, QT prolonged, Torsades
- GI issues
- Dizzy, HA, tremor
Quinidine contraindications
- WPW
- AV block
- Digitalis toxicity
- Myasthenia gravis
Lidocaine (class, indications, key features)
- Class IB Na channel blocker
- VT/VF when defib/epi fails and amiodarone unavailable
- Digoxin induced VT, monomorphic VT
- Efficacy is reduced over duration of arrest
- “Safest” of all Na channel blockers
What is the safest of all Na channel blockers?
Lidocaine
How is lidocaine metabolized? What is its half life?
- CYP1A2, hepatic blood flow determines rate (significantly impaired during arrest)
- 1.8 hours
Lidocaine serious adverse events
- Arrhythmias
- Seizure, tremor, paresthesias
Mexiletine (class, indications)
- Class IB Na blocker
- Used for conversion and maintenance when other agents fail
How is mexiletine metabolized? What is its half life?
- CYP2D6 and 1A2 (higher doses needed in smokers)
- Variable half life (6-17 hrs)
Mexiletine adverse events
- GI
- Dizziness
- Arrhythmias
- Tremor, ataxia
Mexiletine contraindications
AV block, cardiogenic shock
Flecainide (class, indications, key features)
- Class IC Na blocker
- SVT, AF induced VT
- Pill in pocket conversion to sinus rhythm, paroxysmal AF
How is flecainide metabolized? What is its half life?
- CYP2D6
- 7-14 hrs in healthy ppl
- 19-22 hrs post-MI
- 27 hrs w/HF and repeated dosing
Flecainide serious adverse events
- AV/BBB, QT prolong
- Dizzy, HA, fatigue
- Dyspnea
Flecainide contraindications
RBBB, AV block, cardiogenic shock