Antiarrhythmics

Question 1

Lidocaine (xylocaine)

Answer 1

Class: antiarrhythmic

MOA: suppresses automaticity and spontaneous depolarization of the ventricles during diastole by altering the flux of sodium ions across cell membranes with little or no effect on the heart rate.

Pharmacokinetics: onset- <3 Min, duration 10-20 minutes, but up to several hours after continuous infusion; HL: 1.5-2 hrs

Indications: vf, pulseless vt, use after successful conversion from VF, Pulseless VT; wide complex tachycardias, ventricular ectopy in the presence of an MI

AR/SE: Cardiac arrest, seizures, anaphylaxis, confusion, drowsiness, N/V

Contraindications: known allergy, 2nd degree type II and 3rd degree av block

Dosage: 1-1.5 mg/kg may repeat at half the initial dose (0.5-0.75 mg/kg) every 5-10 min up to a total of 3mg/kg. (for continuous infusions: 2-4 mg/min)

Question 2

Procainamide (pronestyl)

Answer 2

Class: antiarrhythmic

MOA: decreases myocardiac excitability and slows conduction velocity; it reduced automaticity in the various pacemakers of the heart.

Pharmacokinetics: onset- 10-30 min, duration- 3-6 hrs; HL: 3 Hrs

Indications: ventricular and atrial arrhythmias including PAC, PVC, VT, atrial tach; maintain NSR after conversion from a-fib or a-flutter

AR/SE: asystole, heart block, ventricular arrhythmias, seizures, diarrhea, N/V, respiratory and cardiac arrest

Contraindications: known allergy, High Degree av block

Dosage: 20-50 mg/min slow IV (max 17 mg/kg)

Question 3

Adenosine (Adenocard)

Answer 3

Class: antiarrhythmic

MOA: restores NSR by interrupting reentry pathways in the AV node and causes coronary artery vasodilation

Pharmacokinetics: onset immediate, duration 30 sec; HL: 10 sec

Indications: converting paroxysmal supraventricular tachycardia (PSVT) and stable wide complex tachycardias to a NSR

AR/SE: shortness of breath, transient arrhythmias, chest pain, hypotension, hyperventilation, burning sensation, light-headedness, facial flushing

Contraindications: known allergy, 2nd or 3rd degree AV block, sick sinus syndrome, irregular afib or polymorphic vtach

Dosage: 6mg rapid IV push; if unsuccessful, repeat in 1-2 minutes at 12mg rapid IV push, may repeat 12 mg dose again if needed.

Special Considerations: (P class C)

Question 4

Verapamil (isoptin)

Answer 4

Class: antiarrhythmic, antianginal, calcium channel blocker

MOA: blocks calcium from moving into the heart muscle cell, which prolongs the conduction of electrical impulses through the av node. Also, dilates arteries.

Pharmacokinetics: onset- 5 Min, duration 10-60 min; HL: 2-8 Hrs

Indications: Narrow complex tachycardias-atrial fibrillation, hypertension, psvt, psvt prohylaxis

AR/SE: sinus bradycardia, CHF,, asystole, AV blocks, hypotension

Contraindications: known allergy, sick sinus syndrome, 2nd or 3rd degree av blocks, severe ventricular dysfunction, cardiogenic shock, severe hypotension. wpw

Dosage: 2.5-5 mg IV over 2 minutes; may be repeated with 5-10 mg after 15-30 min

Special considerations: do not administer to pts receiving IV beta blockers, increases risk of CHF, bradycardia, and asystole

Question 5

Diltiazem (Cardizem)

Answer 5

Class: calcium channel blocker, antiarrhythmic, antihypertensive, antianginal

MOA: inhibits transport of calcium into myocardial and vascular smooth muscle cells. Slows conduction through the av node

Pharmacokinetics: onset 3 min, duration: 1-3 hrs; Hl: 2 hrs
Indications: management of angina, SVT, rapid afib, rapid aflutter

AR/SE: sinus bradycardia, CHF,, asystole, AV blocks, hypotension

Contraindications: known allergy, sick sinus syndrome, 2nd & 3rd degree AV blocks, recent MI, pulmonary congestion, systolic BP lower than 90. wpw

Dosage: 0.25mg/kg IV over 2 minutes may repeat in 15 minutes at 0.35mg/kg

Special considerations: do not administer to pts receiving IV beta blockers, increases risk of CHF, bradycardia, and asystole

Question 6

Amiodarone (cordarone)

Answer 6

Class: antiarhytmic

MOA: Prolongs the action potential and the refractory period; slows the sinus rate, increasing the PR interval and the QT interval; and decreases peripheral vascular resistance

Pharmacokinetics: onset- 1-3 min IV; duration varies; Hl: 40-55 days

Indications: management of Ventricular Fibrillation (VF) and pulseless Ventricular Tachycardia (PVT); can be used for other life-threatening tachyarrhythmias as well

AR/SE: ARDS, Pulmonary Fibrosis, CHF, Pulmonary Toxicity, deteriorating of arrhythmias, bradycaridia, hypotension, dizziness, fatigue, malaise, N/V, constipation, anorexia, tremor

Contraindications: known allergy, pts with cardiogenic shock, pts with 2nd or 3rd decree av blocks

Dosage: cardiac arrest-300 mg IV bolus, may repeat in 3-5 minutes @ 150 mg IV bolus; ventricular arrhythmias- 150 mg over 10 minutes followed by 360 mg over 6 hours.

Special Considerations: (P class D) enters breast milk and causes harm to neonate;

Question 7

Magnesium sulfate

Answer 7

Class: mineral/electrolyte, antiarrhythmic

MOA: plays important role in neurotransmission and muscular activity

Pharmacokinetics: Onset- Immediate, Duration-1hr

Indications: torsades de pointes, hypertension,

AR/SE: diarrhea, bradycardia, respiratory depression, drowsiness, hypotension, hypothermia

Contraindications: known allergy,persistent severe hypertension hypermagnesemia, hypocalcemia, heart block

Dosage: torsades-1-2 grams over 5-60 minutes (followed by infusion 0.5-1 g/hr)