| What are classes of antiarrhythmatic drugs? | Class I (Quinidine, Lidcaine, Flecainide - Sodium action)
Class II (Esmolol, Metoprolol, Propanolol - beta blockers)
Class III (Amiodarone, Sotalol - Potassium)
Class IV (Verapamil, Diltiazem - Ca channel blockers) |
| Give table of classes of antiarrythmic drugs. | . |
| What is mechanism of action of class IA agents? | Quinidine binds to open and inactivate Na+ channels prevent Na+ influx in phase 0, slows the rate of depolarization and conduction, prolong repolarization by blocking some K+ channels, increase ventricular effective refractory period ERP, slows conduction
Other actions (mild a antagonist and anticholinergic) |
| What are pharmacokinetics, therapeutic uses and adverse effects of quinidine? | Pharmacokinetics (Rapid and almost completely absorbed after oral admin, extensive metabolism by CYP3A4)
Therapeutic Uses (Quinidine used in tx of tachyarrhythmias (A/V tachy))
Adverse Effects (Has atropine like effect [dry mouth, headache, blurred vision], develop some arrythmias, SA/AV blocks) |
| What is mechanism of action of class IB agents? | Lidocaine, little effect on rate of depolarization, decrease duration of action potential by shortening repolarization (Phase 3 action)
Rapidly dissociate Na+ channels, manifests when cardiac ell is firing rapidly, useful in treating ventricular tachy prevents re-entry of abnormal electrical impulses by shortening AP. |
| What are therapeutic uses, pharmacokinetics and adverse effects of Lidocaine? | V Tach, IV given due to extensive 1st pass, CNS toxicity |
| What is mechanism of action of class IC agents Flecainide? | Bind slowly Na+ channels, slow phase 0 very much slows conduction, little effect on duration of AP or refractory period |
| What are uses, adverse effects and contraindications of Flecainide? | Uses (refractory V arrythmia)
effects (visual disturbance, dizziness)
Contraindication (hypersensitivity, 2nd/3rd degree AV block) |
| Table of Class I antiarrythmic drugs comparison | . |
| How is beta blockers use as antiarrythmatics? | Diminish depolarization, depress automaticity, prolong AV conduction and decrease HR and cotractility.
Useful in tachyarrhythmias caused by increased sympathetic activity, SVT
Includes Metoprolol, Esmolol. |
| What are uses, pharmacokinetics and effects of metoprolol and esmolol? | Metoprolol:
• most widely used in the treatment of cardiac
arrhythmias (selective)
• Compared to nonselective beta blockers, it reduces
the risk of bronchospasm
• It is extensively metabolized in the liver
• It has CNS penetration (less than propranolol)
Esmolol:
• Very-short-acting β-blocker
• used for IV administration in acute arrhythmias that
occur during surgery or emergency situations.
• It has a fast onset of action and a Short half-life
• Rapidly metabolized by esterases in red blood cells
Esmolol is ideal for acute episodes of arrhythmias with
limited adverse effects |
| What are class III antiarrythmatics? | K+ Blockers, Prolong phase 3 w/out altering phase 0, prolong duration of AP and ERP, can block Na+ also, slows cardiac automaticity and AV conduction as Ca channel blockers, weak beta antagonist action.
Imp for recurrent and refractory ventricular and SVT |
| What are uses of amiodarone? | Complex antiarrythmatic Classes II and IV
Used in tx of severe refractory SVT and VT, mainstay of therapy of A Fib/Flut, it is the most commonly employed antiarrythmatic and is least proarrythmatic |
| What are adverse effects of amiodarone? | Gray-Blue discoloration & photo dermatitis, corneal microdeposits, pulmonary fibrosis (Serious), Thyroid dysfunction (contains Iodine), Hepatic impairment, Neuro effects, taken up by adipose.
Low doses and close monitoring reduces toxicity retaining clinical efficacy |
| What is action of class IV Antiarrythmatics? | Ca Channel Blockers, decrease influx of Ca2+ in spontaneous depolarization, slow conductance of Ca2+ in AV node, slow conduction, prolong ERP dependent on Ca2+ like AV node |
| What are therapeutic uses of class IV antriarrythmatics? | Verapamil and diltiazem are more effective against atrial than against ventricular arrhythmias.
They are useful in treating reentrant supraventricular tachycardia and inreducing the ventricular rate in atrial flutter and fibrillation (ventricular ratereduction). |
| What are guidlines for atrial arrythmias? | . |
| What are guidlines for SVT and VT? | . |
