Antiarrhythmics

Lidocaine

Adult Dosing

• Loading dose = 1-1.5 mg/kg
  • Additional boluses of 0.5-0.75 mg/kg q5-10min up to max of 3mg/kg
  • If effective start infusion of 2mg/min

Contraindications

• High SA or AV block

Indications

• Treatment of ventricular arrhythmias and ectopy
  • Considered 2nd-line to amiodarone for tx of V-fib and pulseless v-tach

Mechanism of Action

• Class Ib
  • Binds to fast Na channels in inactive state thereby inhibiting recovery after repolarization
  • Acts preferentially on ischemic tissue
    • Elevates V-fib threshold
    • Suppresses ventricular ectopy
• Little effect on vascular tone, contractility or cardiac output

Adverse Drug Rxns

• CNS
  • Abrupt change in MS, drowsiness, confusion, sz

Kinetics

• Onset of action = 45-90s
• Duration of action = 10-20min

Labetalol

Adult Dosing

• Bolus dosing
  • 20mg IV followed by 40-80mg q10min up to total of 300mg
• Infusion dosing
  • 0.5-2mg/min

Indications

• HTN in setting of myocardial ischemia
• HTN in setting of neurologic injury
• HTN in setting of preeclampsia/eclampsia

Mechanism of Action

• Class II - Nonselective beta blocker
• Alpha1 blocker

Adverse Drug Rxns

• Orthostatic hypotension

Kinetics

• Onset of action = 2-5min (IV)
• Duration of action = 2-4hr (IV)

Sotalol

Adult Dosing

• 80mg PO BID

Indications

• Suppression of ventricular arrhythmias refractory to other meds
• Suppression of SVT, a-fib

Mechanism of Action

• Class II - Nonselective beta-blocker
• Class III effects (prolongs repol and refractoriness)

Adverse Drug Rxns

• Hypotension, bradycardia
• Proarrhythmia (esp in pts w/ hypokalemia)

Kinetics

• Onset of action = 2-3hr
• Duration of action = 24hr

Amiodarone

Adult Dosing

• V-fib/pulseless V-tach
  • Loading dose = 300mg IV bolus followed by 150mg bolus prn
• Stable V-tach or SVT
  • Loading dose = 150mg IV in 100mL D5W over 10min
    • Follow by infusion of 1mg/min x 6hr; 0.5mg/min thereafter

Contraindications

• Iodine or shellfish allergy
• Pregnancy

Indications

• Ventricular and supraventricular arrhythmias
• 1st line for pulseless V-tach/V-fib
• Used for atrial arrhythmias in pts w/ decr EF

Mechanism of Action

• Class III - Inhibits potassium channels
  • Impairs SA and AV node conduction
  • Decreases automaticity
  • Prolongs refractory period in accessory pathways
• Also has class I & II properties

Adverse Drug Rxns

• Bradycardia, hypotension
• Prolonged QT

Ibutilide

Adult Dosing

• Loading dose = 1mg IV in 50mL D5W over 10min (wt>60kg)
• Loading dose = 0.01mg/kg IV in 50mL D5W over 10min (wt<60kg)
• Dose may be repeated 10min after completion of 1st dose

Indications

• Rapid conversion of recent-onset A-fib/flutter to NSR

Mechanism of Action

• Class III - Prolongs AP and refractory period

Adverse Drug Rxns

• QT prolongation, V-tach, torsades
• Observe for 4hr after infusion

Kinetics

• Onset of action = 20-30min
• Duration of action = 24hr

Diltiazem

Adult Dosing

• Loading dose = 0.25mg/kg (max=20mg) IV bolus over 2min
  • If ineffective after 15min: 0.35mg/g (max=25mg) over 2min
  • If effective: Start infusion at 5-15mg/hr

Contraindications

• Wide-complex tachycardia due to bypass tract

Indications

• Conversion of PSVT to NSR
• Slow RVR in a-fib/flutter

Mechanism of Action

• Class IV - Inhibits Ca influx
  • Slows AV nodal conduction

Adverse Drug Rxns

Bradycardia, CHF, AV block, BBB, hypotension

Kinetics

• Onset of action = 2-3min (IV)
• Duration of action = 1-3hr (IV)

Atropine

Adult Dosing

• Loading dose = 0.5mg rapid IV bolus q3-5min (max = 0.04 milligram/kg)
• May be given IM, IO, SC

Indications

• Symptomatic sinus or AV nodal bradycardia

Mechanism of Action

• Parasympatholytic
  • Increases sinus/AV conduction

Adverse Drug Rxns

• Increased O2 consumption
• If given slowly (or <0.5mg) may lead to paradoxical bradycardia

Kinetics

• Onset of action = 2-4min
• Duration of action = 5hr

Adenosine

Adult Dosing

• 6mg rapid IV bolus over 1-2s
  • If ineffective can try 12mg 2min later
    • If still ineffective can try another 12mg

Contraindications

• 2nd, 3rd AV block
• Sick sinus syndrome
• Reentrant SVTs not involving AV node are not terminated
• No effect on anterograde WPW

Indications

• Conversion of reentrant PSVT to NSR

Mechanism of Action

• Negative inotropic, dromotropic, chronotropic effects
• Transient AV nodal block

Adverse Drug Rxns

• Bronchoconstriction (responds to bronchodilators)
• Bradyarrhythmia
• Hypotension (if given too slowly)

Kinetics

Onset of action = 20-30s Duration of action = 60-90s

Digoxin

Adult Dosing

• Loading dose = 0.25 mg IV q2hr until effect (max total = 1.5 mg

Contraindications

• WPW
  • Increases conduction velocity in atrial tissue

Indications

• RVR control in a-fib/flutter, PSVT

Mechanism of Action

• Inhibits NaK pump
  • Positive inotropy
• Negative chronotropy/dromotropy
  • Indirect vagal stimulator

Adverse Drug Rxns

• GI - N/V, diarrhea, abd pain
• CV - Bradycardia, SA/AV block, ventr arrhythmias

Kinetics

Onset of action = 1.5-4hr (IV)

Isoproterenol

Adult Dosing

2-10mcg/min IV by continuous infusion

Indications

• Refractory torsades
• Refractory symptomatic bradycardia

Mechanism of Action

• Beta agonist

Adverse Drug Rxns

• Dramatic increase in O2 demand
• V-tach (use lowest dose possible)

Kinetics

• Onset of action = 1-5min
• Duration of action = 1-2hr

Magnesium

Adult Dosing

• Loading dose = 1-2gm in 10mL D5W over 1-2min (cardiac arrest)
• Loading dose = 1-4gm in 50-100 D5W over 20-60min (spontaneous circulation)

Indications

• Torsades
• Refractory v-tach/fib (regardless of Mg level)

Mechanism of Action

• Increases vasomotor tone
• Prolongs AV conduction; prolongs refractoriness

Adverse Drug Rxns

• Hypotension (rare)

Kinetics

• Onset of action = Immediate
• Duration of action = 30min

Source

Tintinalli