Antiarrhythmic Classifications

What is the mechanism of action of class IA antiarrhythmics?

block fast Na+ channels decrease rate of phase 0 depolarization decrease contractility

Which drugs are class IA antiarrhythmics?

procainamide quinidine disopyramide moricizine

What is the mechanism of action of class IB drugs?

minimally block fast sodium (Na+) channels shorten repolarization in late phase 2 shorten the duration of action potential and refractory period

Which drugs are class IB antiarrhythmics?

lidocaine mexilitine tocainide phenytoin Signup and view all the answers

Class IB drugs are used for ___________ arrhythmias?

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Is class IC first line treatment?

No - it is reserved for use in refractory ventricular arrhythmias. Signup and view all the answers

What is the mechanism of action of class IC antiarrhythmic drugs?

block fast sodium channels depress phase 0 depolarization markedly inhibit the His-Purkinje conduction system Signup and view all the answers

Which drugs are class IC antiarrhythmics?

flecainide propafenone Signup and view all the answers

The class II drugs are ________________.

beta blockers Signup and view all the answers

What is the MOA of class II antiarrhythmics?

decrease the rate of spontaneous phase 4 depolarization decrease SNS activity decrease HR, conduction, contractility prolong PR interval Signup and view all the answers

Which drugs are class II antiarrhythmics?

esmolol propranolol acebutolol Signup and view all the answers

Which drugs are class III antiarrhythmics?

amiodarone sotalol ibutilide dofetilide bretylium Signup and view all the answers

What is the MOA of class III drugs?

block potassium in phase 3 increase duration of action potential and refractory period decrease the time spent in "excitation" Signup and view all the answers

What are characteristics of amiodarone, and which receptors & channels does it block?

exhibits class I, II, & IV properties. class I: blocks Na+ channels class II: blocks beta receptors class IV: blocks calcium channels amiodarone blocks: Na, K, Ca, alpha and beta Signup and view all the answers

Which drugs are class IV?

nondihydropyridine calcium channel blockers--verapamil and diltiazem Signup and view all the answers

What is the MOA of class IV antiarrhythmics?

block slow calcium channels slow conduction in SA and AV nodes decrease contractility Signup and view all the answers

What phase of the nodal action potential does digitalis work to slow HR?

phase 4 - digitalis works to slow the HR by slowing phase 4 depolarization in cells in the SA and AV nodes Signup and view all the answers

Which phase of the nodal action potential do calcium channel blockers work to slow the HR?

phase 4 - CCBs (verapamil, diltiazem) slow HR by slowing down phase 4 depolarization of SA node and AV node cells. Signup and view all the answers

What phase dose lidocaine and phenytoin work on to control ventricular arrhythmias?

lidocaine and phenytoin suppress spontaneous phase 4 depolarization in ventricular cells Signup and view all the answers

What phase of the ventricular action potential do CCBs work?

CCBs work on phase 2 of the ventricular action potential. Signup and view all the answers

What happens to phase 2 (plateau) when there is hypocalcemia?

With hypocalcemia, Ca2+ diffuses into the cell more slowly. This prolongs the plateau phase of the action potential. Signup and view all the answers

What happens to phase 2 (plateau) when there is hypercalcemia?

Hypercalcemia causes calcium to diffuse into the cell much faster, which shortens the duration of the plateau phase. Signup and view all the answers