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Antiarrhythmic Drugs

Class1(B):Shorten the duration of action potential. Class1(C) : No effect on the duration of action or refractory period.Class 11 : -adrenoceptor blockers.Class 111: K channel blockers,Prolong duration of action potential and refractory period.. Class1V : Ca channel blockers.. Class V: Misce

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Antiarrhythmic Drugs

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    1. Antiarrhythmic Drugs Class 1 : Na+ channel blockers Local anaesthetic effect -ve inotropic action Class 1( A ): prolongs duration of action potential & refractory period. Have K+ channel blocking effect Antimuscarinic & hypotensive effects.

    2. Class1(B):Shorten the duration of action potential Class1(C) : No effect on the duration of action or refractory period. Class 11 : ß-adrenoceptor blockers. Class 111: K+ channel blockers, Prolong duration of action potential and refractory period.

    3. Class1V : Ca++ channel blockers. Class V: Miscellaneous group.

    4. Class 1(A) Quinidine Cardiac effects: Block sodium channel Block potassium channel -ve inotropic effect Antimuscarinic effect (prolong A.V.conduction). ?duration of action potential & refractory periods of atrium & ventricles.

    5. ECG changes Prolong Q-T interval Widening QRS complex

    6. Extra cardiac effects a- blocking effect (hypotension) Antimuscarinic effect

    7. Pharmacokinetics Well absorber orally Metabolized in liver Usually given as slow release formulation I.M. painful,I.V. is toxic

    8. Clinical uses Atrial flutter & fibrillation it returns the rhythm back to normal. N.B. Better to be preceeded by drugs that slow conduction in A.V.N. Used in treatment of ventricular arrhythmia.

    9. Adverse effects 1- Cardiac effects A) Due to antimuscarinic effect ,in A.F.or A.F. may precipitate ventricular fibrillation B) Syncope C)Torsade de pointes D) Cardiac stand still(in patients with sick sinus syndrome ).

    10. Extracardiac adverse effects Hypotension Cinchonism (headache, dizziness,tinnitus,deafness ) Hypersensitivity reactions (hepatitis,angioneurotic edema) GIT, diarrhea,nausea,vomiting

    11. Disopyramide As quinidine but : Has marked antimuscarinic effect. Is only available for oral use In renal impairment dosage must be adjusted

    12. Adverse effects Can precipitate all of the electrophysiologic disturbance as quinidine. Potent –Ve inotropic effect on heart may cause heart failure . Antimuscarinic effects

    13. Contraindications Heart failure Glaucoma Prostatic hypertrophy Constipation Sick sinus syndrome

    14. Clinical uses Used only for the treatment of ventricular arrhythmias.

    15. Class 1(B) Lidocaine Shorten the duration of A.P.& R.P. Effective in ventricular arrhythmias.

    16. Pharmacokinetics Well absorbed after oral administration but subjected to extensive first pass hepatic metabolism, only 3% reach general circulation. Given only by I.V. route Excreted via kidney . Half-life 2hrs.

    17. Therapeutic uses A)First drug of choice in treatment of ventricular arrhythmias due to 1-Acute myocardial infarction 2-Digitalis toxicity 3-Anaesthesia 4-Open heart surgery B)Local anaesthetic drug

    18. Adverse effects 1-Neurological effects : Paresthesias, tremor,nausea of central origin, convulsions(contraindicated in epileptic patients ). 2-Arrhythmias (least cardiotoxic of all Na+ channel blockers ). 3-Hypotension (depress myocardial contractility ).

    19. Propafenone Has a weak ß-blocking effect. Used for supraventricular arrhythmias. The most common adverse effects are : Metallic taste, constipation ,arrhythmias.

    20. Moricizine Has long half-life Used for ventricular arrhythmias Common adverse effects are : Dizziness ,nausea,arrhythmias.

    21. Class 11 Beta-Adrenoceptor-Blocking Drugs. Effective in atrial & ventricular arrhythmias that associated with : 1-Increase in sympathetic activity e.g.emotion,stress,thyrotoxicosis. 2-Digitalis induce arrhythmias. 3-With quinidine in A.F.& A.F. 4-Esmolol is a short-acting used mainly for intraoperative ´ arrhythmias(ICU).

    22. Class 111 Potassium channel blockers ( Drugs that Prolong duration of action potential & refractory period ).

    23. Bretylium Has ß- blocking effect. Initial release of catecholamines so may precipitate ventricular arrhythmias. Available only for intravenous use. Used in an emergency cases as during attempted resuscitation from ventricular fibrillation when lidocaine or cardioversion failed.

    24. Adverse effects Arrhythmias Postural hypotension(ß-blocking effect). Nausea & vomiting

    25. Sotalol Has ß-blocking effect. Is used for the treatment of : 1-Life- threatening ventricular arrhythmias. 2-To maintain sinus rhythm in patients with atrial fibrillation. 3- For treatment of supra & ventricular arrhythmias in pediatric age group.

    26. Amiodarone A) cardiac effects Has a broad actions : Sodium channel blocking effect Potassium channel action Calcium channel blocking action ß- adrenoceptor blocking action

    27. Amiodarone(cont.) B) Extracardiac effect Peripheral vasodilation

    28. Pharmacokinetics Given orally Slow onset of action Long half-life(13-103 hrs ). Cumulative drug Eliminated by liver mostly as active metabolites. Precipitate in different tissues causing side effects.

    29. Clinical uses 1- Refractory ventricular arrhythmias. 2- Arrhythmias associated with Wolff Parkinson syndrome.

    30. Adverse effects 1- Gray- blue skin discoloration & photodermatitis . 2-Corneal microdeposits ?corneal opacity ,optic neuritis,blindness ,yellowish brown haloes. 3-pulmonary fibrosis

    31. Adverse effects (cont.) 4-hypo or hyperthyroidism 5-Nausea & constipation 6-Hepatic impairment 7- neurological effects 8-A-V block & bradycardia

    32. Drug interactions 1- Oral anticoagulant ?bleeding 2-Digoxin?digoxin toxicity 3-ß- blockers ?additive effect

    33. Class 1V Calcium channel blockers E.g. Verapamil, Diltiazem, Bepridil. Their main site of action is A.V.N. Effective only in atrial arrhythmias(tachycardia,A.F.,A.F

    34. Class 1V (cont.) They are the second drugs of choice for paroxysmal supraventricular tachycardia. Not effective in Wolff Parkinson White syndrome.

    35. Adverse effects -Ve inotropic effect causes H.F. A-V block Bepridil prolongs Q-T interval causing torsade de pointes.

    36. Class V 1- Adenosine Binds to adenosine receptors (A1&A2)?opening K+ channel??outward of K+?hyperpolarization. It ? influx of calcium It ?activity of cAMP

    37. Pharmacokinetics Rapid onset of action (10 seconds). Short duration of action Given as I.V. bolus injection Its main site of action A.V.N. First drug of choice in paroxysmal supraventricular tachycardia.

    38. Adverse effects Bronchospasm Chest pain Shortness of breath Flushing A-V block Headache ,hypotension,paresthesias.

    39. Contraindications Bronchial asthma A-V block

    40. magnesium Used in: 1- Digitalis -induced arrhythmias 2-Torsade de pointes 3-Sinus tachycardia

    41. Potassium Used in: Digitalis - induced arrhythmias

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