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CVS Pharmacology
Cardiovascular system pharmacology- Anti Arrhythmic Drugs
| Question | Answer |
|---|---|
| Very important fact about anti-arrhythmic drugs? | Very toxic |
| Classes of anti-arrhythmic drugs? | 1,2,3, and 4 |
| Class 1 drugs are what type of drugs? | Sodium channel blockers |
| Class 2 drugs are what type of drugs? | Beta blockers |
| Class 3 drugs are what type of drugs? | Potassium channel blockers |
| Class 4 drugs are what type of drugs? | Calcium channel blockers |
| Mechanism of anti-arrhythmic drugs: | Readily bind to activated channels or inactivated channels, but bind poorly to rested channels, so normal cells release the drugs quickly |
| Increased dosage of anti-arrhythmic drugs can cause? | Loss of selectivity, leading to drug induced arrhythmia |
| In what other cases can these anti-arrhythmic drugs cause arrhythmia? | 1) Fast heart rates, 2) Acidosis 3) Hyperkalemia 4) Ischemia |
| What other therapies can we try before using drugs? | 1) Surgery 2) Radiofrequency Catheter Ablation 3) Implantable Cardioverter- Defibrillator (ICD) 4) Gene therapy |
| What are the risk factors of Torsade de Pointes? | 1) Bradycardia. 2) Hypokalemia. 3) Decreased Triggered upstrokes. 4) Drugs which increase APD. |
| Treatment of Torsade de Pointes? | 1) K+ 2) Triggered upstrokes (B-Blockers or Mg++) 3) APD (Pacemaker or isoproterenol). |
| TdP is also known as: | Polymorphic Ventricular Fibrillation |
| Causes of TdP: | 1) Familial long QT interval 2) Drug - Induced (drugs which prolong APD) |
| Cardiac Causes of arrhythmia: | 1) Ischemic heart disease. 2) Inflammation. 3) Trauma, most commonly after heart surgery 4) Congestive heart failure 5) Hypotension |
| Non-cardiac of arrhythmia: | 1) Electrolyte imbalance. 2) Acid-Base imbalance. 3) Hypoxia. 4) Drugs: Digitalis, Anesthetics, Tricyclic, Diuretics, Bronchodilators. 5) G.I. reflexes. 6) Neural reflexes |
| Example of Class 1A drug: | Disopyramide |
| Example of a Class 1B drug: | Lidocaine |
| Example of a Class 2 drug: | Propanolol Atenolol |
| Example of a Class 3 drug: | Amiodarone Sotalol |
| Example of a Class 4 drug: | Verapamil |
| Which substances increase potassium channel activation? | Adenosine Digoxin |
| Which substance causes Calcium channel block? | Magnesium chloride |
| Electrophysiological actions of Class 1 drugs? | Reduced rate of depolarization of action potential Increased ERP (refractory period) Decrease AV conduction |
| Electrophysiological actions of Class 2 drugs? | Slowed pacemaker activity Increased AV refactory period |
| Electrophysiological actions of Class 3 drugs? | Increase action potential duration Increased ERP |
| Electrophysiological actions of Class 4 drugs? | Decrease APD (Action potential duration) Slowed AV conduction |
| Potassium channel activators have which physiological action? | Slowed AV conduction |
| Clinical use of Class 1 drugs: | Ventricular Fibrillation associated with MI |
| Clinical use of Class 2 drugs: | Dysrhythmia prevention in MI Paroxysmal A-Fib due to sympathetic activity |
| Clinical use of Class 3 drugs: | A-fib Ventricular fibrillation |
| Clinical use of Class 4 drugs: | Supraventricular tachycardias A-fib |
| Clinical use of adenosine? | IV for supraventricular tachycardias |
| Clinical use of digoxin? | A-fib |
| Clinical use of Magnesium chloride: | Ventricular fibrillation Digoxin toxicity |
| Phase 2 of APD can be activated by sympathetic activity inhibited by | Calcium-channel blockers beta blockers |
| Phase 3 can be inhibited by | Class 3 drugs |
| Phase 4 can be inhibited by | class 2 drugs |
| Phase 0 inhibited by: | Class 1 drugs |
| Class 1A drugs: | Double Quarter Pounder Disopyramide Quinidine Procainamide |
| Which Class 1A drugs is the prototype? | Quinidine is the prototype, derived from Quinine which is an antimalarial, from cinchona tree |
| Side effects of Quinidine: | Cinchonism, characterised by headache, dizziness, tinnitus Diarrhea in 33% of patients Thrombocytopenia TdP symptoms Increases serum digoxin and Warfarin effects |
| What does Quinidine do? | Inhibits a and muscarinic receptors, prolongs action potential duration and QRS |
| Clinical use of Quinidine: | used with patients with atrial/ventricular arrythmias but NORMAL HEART |
| Characteristics of Procainamide: | Oral Short half life Lupus- like symptoms |
| Characteristics of Dispyramide: | More anticholinergic effects but less diarrhea than quinidine |
| Class 1B drugs: | Lettuce, Mayo, Tomato, Potato Lidocaine, Mexiletine, Tocainide, Phenytoin |
| Lidocaine is | A widely used local anesthetic agent |
| When is Lidocaine used? | When the patient is NOT hypokalemic Ventricular arrythmias in Post MI patients to prevents V-A (Used to be the drug of choice) Not effective in atrial arrhythmias |
| Lidocaine is given: | Intravenously |
| Side effects of Lidocaine: | CNS Hypotension with large doses Least cardiotoxic as side-effects not cardiac, no sudden death |
| What are Tocainide and Mexilitine? | Oral analogs of lidocaine |
| Side effects of Tocainide and Mexilitine | GI and neurologic side-effects |
| Phenytoin is: | Anti-epileptic drug, for special conditions of cardiac arrhythmias: digitalis or congenital heart surgery, or congenital prologned QT interval |
| Class 1c drugs are usually used as | A last resort |
| Class 1C drugs are: | Fries Please Flecainide Propafenone |
| Function of Flecainide: | Blocks K channels |
| Uses of Flecainide: | Proarrhythmic Effective in supra ventricular tachycardia in normal hearts |
| Consequence of Flecainide use: | Sudden death |
| Propafenone has what function? | Beta-blocking and channel blocking activity NO effect on QT Same use and milder effects from Flecainide |
| Class 2 drugs end with: | -olol |
| What is the prototype of this class of drugs? | Propranolol |
| What is the use of Propranolol? | Used to treat hypertension, but found to be very effective to treat arrhythmias from post-MI |
| In all doses, propranolol is: | Anti-arrhythmic |
| What other class 2 drugs are used? | 1) Esmolol IV injection 2) Acebutolol |
| What are the characteristics of Esmolol? | 1) Very short acting, so used in surgeries or acute arrhythmias, 2) B1 selective 3) NO membrane stablizaition effect (unlike propranolol) |
| What are some general characteristics of class 3 drugs? | combined activity of class 1,2,4, wide-spectrum of activity |
| When is Amidarone given? | For life-threatening atrial and ventricular arrhythmias Given IV to induce peripheral vasodilation |
| Even though Amidarone prolongs QT, what does not occur? | TdP |
| Because Amidarone is slow acting, it needs: | A loading dose (given IV) and maintained orally |
| What is the half life of Amidarone? | 25-110 days |
| Side effects of Amidarone: | Cardiac Toxicity Lung fibrosis (most common) Liver toxicity Increases digoxin and anticoagulants levels as it is metabolized by CYP34A4 |
| What is Sotalol? | beta blocker with class 3 action |
| What is Bretylium tosylate? | Anti-Hypertensive |
| When is was Bretylium tosylate used? | life-threatening condition of VF after failure of cardiversion or lidocaine |
| Class 4 drugs: | Verapamil and Diltiazem |
| Function of class 4 drugs? | Block activated and inactivated L-type Ca channels, for Paroxysmal Supraventricular Tachycardia |
| Class 4 drugs were the drugs of choice in: | Paroxysmal Supraventricular Tachycardia |
| Now, the DOC of Paroxysmal Supraventricular Tachycardia is | Adenosine |
| Calcium Channel blockers are being investigated for: | Treatment in cancer |
| Digoxin is used for treatment of | Heart failure Atrial arrhythmias |
| Side Effects of digoxin: | Ventricular arrhythmias Toxicity Potential Heart block due to inceased AV |
| Magnesium works to: | Block multiple channels Hypertensive agent (when there is toxemia of pregnancy) |
| Clinical uses of Magnesium: | Effective in refractory digitalis only in hypomagnesemic patients (IV) and Tdp with hypomagnesemic patients Hypertensive agent (when there is toxemia of pregnancy) |
| Potassium is used for: | Digitalis induced arrhythmia with hypokalemia |
| DOA for adenosine is: | Max 15 seconds |
| Adenosine used for: | supraventricular tacchyardia - DOC |
| Which substances reduce the activity of adenosine? | 1) Theophylline 2) Caffeine |
| Most important side effect of adenosine: | Transient flushing |
Created by:
Ulaisl
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