Antiarrythmics

Cards (21)

  • Class 1A:Sodium channel blockers Drugs • Quinidine • Disopyramide • Procainamide Mechanism of action • Binds to both active and inactivated Na+ channels • Reduce slope of phase 4 depolarization • Inhibits K+ channels • Increases duration of AP
  • Quinidine metabolism and adverse effects:
    • Liver CYP3A4
    • Cinchonism (dry lips, mouth, tinitius)
  • Drugs of class 1B:
    1. Lidocaine
    2. Mexiletine
    3. Tocainide
  • Mechanism of class 1b
    • shorten phase 3 - repol
    • decrease action potential duration
  • Lidocaine metabolism and AE:
    1. Metabolised by CYP3A4 but estensive FPE so IV preferred
    2. AE: Nystagmus, confusion, negative inotrope
  • Slope showing effect of which class:
    Class 1b due to reduced duration of action potential and shortening of phase 3
  • Class 1c
    • Flecainide
    • Propafenone
  • Class 1c MOA:
    Significantly slow phase 0 depolarization
    • Strong effect on Na+ channels
    • Increase in threshold potential
    • Blockade of K+ channels (Flecainide)
  • Flecanide useful for atrial flutter and fibrillation
  • Flecainide is restricted to use in structurally normal hearts
  • Beta blockers diminish phase 4 and have a negative inotropic effect
  • Indications of beta blockers
    Treatment of supraventricular tachy-arrhythmias (AF, atrial flutter)
    Increase survival in patients with heart failure and myocardial infarction
  • Metoprolol is B1 selective e.g. reduced risk of bronchospasm
  • Esmolol is ultra short acting and has a rapid onsent (selective B1)
  • Class 3 agents include Amiodarone • Dronedarone • Sotalol, Ibutilide which are potassium channel blockers
  • class 3 prolong phase 3 repolarization therefore prolonging duration of AP
  • Amiodarone adverse effects
    • Has iodine ions
    • Thyroid disorders
    • Pulmonary fibrosis
    • hepatotoxicity , skin discoloration
  • Class 3 Dronedarone contraindications
    • Heart failure
    • Permanent AF
  • Class 4 are CCBs and the non dihydropyridines include
    • Diltiazem and Verapamil
  • CCBs MOA:
    • Prevent depolarization
    • BUT AVOID IN HF
  • Digoxin MOA
    • Inhibits Na-K Atpase preventing Na out and Calcium in
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