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CVS Pharmacology
Dr. Maleque's CVS Drugs
Question | Answer |
---|---|
Class I Antiarrhythmic Drugs | Na+ Channel Blockers |
Class II Antiarrhythmic Drugs | Beta-adrenoreceptor Blockers |
Class III Antiarrhyhtmic Drugs | Potassium Channel Blockers |
Class IV Antiarrhythmic Drugs | Calcium Channel Blockers |
Class IA | Quinidine, Procainamide, Disopyramide, Amiodarone |
Quinidine - MOA | Slows upstroke AP & conduction; prolongs QRS duration via blockage of Na+ Channels; AP prolongation via K+ Channel blockade |
Quinidine - Toxicity | QT interval prolongation; torsade de points; slowed conduction |
Procainamide - MOA | Slows upstroke AP & conduction; prolongs QRS duration via blockage of Na+ Channels; AP prolongation via K+ Channel blockade; not as effective against ectopic pacemakers (quinidine does); effective in depolarized cells |
Procainamide - Toxicity | Excessive AP & QT interval prolongation; torsades de pointes; syncope; slow conduction; lupus-like syndrome (arthralgia/arthritis); increased antinuclear antibody |
Disopyramide - MOA | Same as quinidine with more antimuscrainic effects; used for superventricular arrhythmias |
Disopyramide - Toxicity | Can precipitate de novo heart failure or can cause heart failure in patients with left ventricular hypertrophy; not a first-line drug in the US |
Amiodarone - MOA | Prolongation of AP (QT interval) via blockage of IKR (Chronic use --> IKS; blocks inactivated sodium channels; low incidence of trosades de pointes |
Amiodarone - Toxicity | Symptomatic bradycardia and heart block; tissue accumulation; photodermatitis (blue-gray spots/UV exposure); thyroid issues; |
Class IB | Lidocaine, Mexiletine, Tocainide |
Lidocaine - MAO | blocks activated & inactivated (ensures greater effect on cells with long APs (Purkinje, ventricular) Na+ Channels; IV/IM routes; |
Lidocaine - Toxicity | One of the least cardiotoxic; Large doses + preexisting conditions = hypotension due to decreased contractility; neurologic effects: paresthesias, hearing disturbed, etc; all short-lived |
Mexiletine - MAO | Orally active congener of lidocaine; Tx of ventricular arrhythmias; same actions as lidocaine |
Mexilitine - Toxicity | Tremor; blurred vision; lethargy (CNS issues |
Phenytoin - MAO | Usually used for epilepsy; similar to lidocaine and mexiletine; |
Phenytoin - Toxicity | Gingival hyperplasia |
Class IC | Flecanide, Propafenone, Encanide |
Flecanide - MAO | Potent Na+ and K+ Channel blocker; NO QT INTERVAL PROLONGATION!!!; No antimuscarinic effects; used for supraventricular contractions and PVCs; eliminated by the kidney and liver |
Flecanide - Toxicity | May cause severe exacerbation of arrhythmia when patient has preexisting ventricular arrhythmias; CAST showed 2.5 increased in premature death |
Propafenone - MAO | Similar effects to the of propanolol; weak beta-blocking activity; Most similar to quinidine, except there's no AP prolongation; metabolized in the liver; used for SVAs |
Propafenone - Toxicity |