- These drugs are used to treat or prevent irregular cardiac rhythm such as impaired conductions or abnormal automaticity.
- There are several factors that cause cardiac arrhythmias e.g MI, ischemia, mechanical injury, electrolyts and pH imbalance, drugs and neurogenic influences.
Classification:
Class I : Na+ Channel blockers ( Membrane stabilizing agents )
IA: Lengthen the AP ( right shift )
- Qunidine
- Disopyramide
- Procainamide [ used in WPW syndrome
-Suppress AV conduction
-Prolong P-R interval
-Prolong QRS, Q-T and Action potential duration
IB: Shorten the AP ( left shift)
- Lignocaine
- Mexiletine
- Phenytoin
- Propafenone
- Flecainide
- Moricizine [Also have calss III property]
Class II: B- Blockers ( Antiadrenergic agents )
- They act by blocking Catecholamine at the B- adrenergic receptors => Decrease sympathetic activity on the heart => Decreae AV node conduction.
- Propanolol (also have class I property)
- Atenolol
- Pindolol
- Sotalol
- Metoprolol / Bisoprolol
- Esmolol
- Acebutolol
- R
- Timolol
[ Remembered as Two(II) PAP SMEAR Test ]
Class III: K+ Channel blockers ( AP widening agents)
These drugs block K+ channel => Prolong repolarization and Effective refractory period (ERP). Do not block Na+ channel hence conduction velocity is not decreased => Prevent Re-entrant arrhythmias
- Bretylium
- Ibutilide
- Amiodarone
- Sotalol
- E-4031
- Dofetilide / Dronedarone
Class IV: Ca++ Channel blockers:
Block Ca++ channel=> Decrease AV node conduction and shortens plateau phase of AP => Reduce cardiac contractility. Avoid in heart failure due to decrease cardiac cantractility.
- Verapamil
- Diltiazem
Class V [ Contraindicated in Ventricular arrhythmias]
- Magnesium sulfate [Used in Torsades de Pointe]
- Adenosine [Used in Supraventricular tachycardia (SPVT)]
- Digoxin [Used in Atrial fibrillation, heart failure]
[ Antiarrhythmic agents mnemonics: One(I) Queen have Pelvic Disease, LMP was More PainFull, two(II) PAP SMEAR Test was done, and three(III) BIASED AP widening agents used are Very Dangerous and MAD]
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