Cardiovascular Critical Care I
APPENDIX A – OVERVIEW OF ANTI-ARRHYTHMICS
Class
MOA
Drug
(available dosage forms)
ECG Effects
Management Considerations and Pearls
Notable Drug Interactions
Defibril-
lation
Threshold
TdP risk
(%)
PR
QRS
QT/QTc
IA
Sodium channel
blockade (inter-
mediate potency)
Quinidine (PO and IV)
↑↓
↑
↑
Different formulations available (no exact conversions)
α-Blockade may contribute to hypotension
Prolonged half-life in CHF and hepatic dysfunction
May require dose adjustments in renal and/or hepatic dysfunction
Enhanced AV node conduction usually requires combination with
AV node-blocking agent
CYP2D6 (inhibitor)
CYP3A4 (substrate and inhibitor)
QT-prolonging drugs
↑
2–8
Procainamide
(IV)
↑
↑
↑
May contribute to hypotension
Metabolized by hepatic acetylation
Active metabolite (NAPA) renally eliminated and has increased
class III properties
Dialyzable
QT-prolonging drugs
↑↓
1–10
Disopyramide
(PO)
↑↓
↑
↑
May require dose adjustments in renal and/or hepatic dysfunction
Potent anticholinergic adverse effects
May be used to treat hypertrophic cardiomyopathy
CYP3A4 (substrate)
QT-prolonging drugs
↑
1–3
IB
Sodium channel
blockade (low
potency)
Lidocaine
(IV)
N/A
N/A
N/A
or
↓
Ventricular arrhythmias only
Increased risk of toxicities in hepatic dysfunction, CHF, and elderly
patients
Enhanced efficacy in ischemic tissue
Adverse effects include CNS depression, somnolence, tremors,
seizures
Lidocaine concentrations may be checked (total: 1.5-5 mcg/mL;
free: 0.5-2 mcg/mL)
CYP3A4 (substrate)
↑
Mexiletine
(PO)
Ventricular arrhythmias only
Prolonged half-life in CHF and hepatic dysfunction
Oral derivative of lidocaine
CYP2D6 (substrate)
CYP1A2
↑
IC
Sodium channel
blockade (high
potency)
Flecainide
(PO)
↑
↑
N/A
or
↑
Useful for AF/flutter in patients without structural heart disease
Increased risk of mortality post-MI (Cardiac Arrhythmia
Suppression Trial [CAST])
Avoid in CHF because of its potent negative inotropic effects
Combine with AV node blocker to prevent rapid atrial flutter
CYP2D6
↑
Propafenone
(PO)
Useful for AF/flutter in patients without structural heart disease
Increased risk of mortality post-MI (CAST trial)
Avoid in CHF because of its potent negative inotropic effects
Combine with AV node blocker to prevent rapid atrial flutter
SR and IR formulations not equivalent
First-pass metabolism
CYP2D6, CYP3A4, CYP1A2
substrate
↑↓