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21 Cards in this Set
- Front
- Back
Class I A
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Blocks fast Na+ channels (activated)--decreases Vmax
Increased APD and ERP block K channels (delayed rectifier current Quinidine Procainamide |
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Quinidine
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Class 1A
Blocks fast Na+ channels--increased threshold for excitability and decreased automaticity. alpha block and vagal stimulation Prolongs QT up to 25% SE: Nausea, diarrhea, vomiting, cinchonism(GI, tinnitus, ocular dysfunction CNS excitation), hypotension, torsades, thrombocytopenia, drug induced SLE, BM depression |
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Quinidine drug interactions
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potent inhibitor of CYP2D6
e.g. codeine to morphine metabolism inhibited--less analgesia hyperkalemia enhances effects displaces digoxin from tissue binding sites & reduces digoxin and digitoxin clearance may oppose AchE inhibitors in MG Phenytoin and phenobarbitol induce Quinidine metabolism--higher dose needed |
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Procainamide
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Class 1A
Blocks fast Na+ less M block than quinidine and no alpha block--more cardiodepressant Orally effective, metabolized via N-acetyltransferase. SE: SLE (30%) w/ slow acetylators, hematotoxicity (thrombo & agranulocytosis), CNS-dizziness and hallucinations, CV effects(torsades) |
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Class 1 B
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Blocks fast Na+ channels--decreases Vmax
less state dependent than class 1A (can block inactivated channels) Preference for tissues partly depolarized (slow conducting and hyopoxic/ischemic Lidocaine Mexiletine Tocainide-no longer used-BM aplasia & pulmonary fibrosis Moricizine--increased mortality, limited use |
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Lidocaine
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Class 1 B anti-arrhytmics
Blocks fast Na+ channels--decreases Vmax & automacity--prefers ischemic or rapidly driven tissues Acute IV use--ventricular arrhytmias Post MI, during open heart surgery or due to cardioversion or digitalis induced arrhytmia SE: Can worsen heart block or CHF--not given routinely anymore CNS tox--seizures in OD--nystagmus is an early sign of toxicity Least cardiotoxic of antiarrhytmics |
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Phenytoin
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Anti-epileptic drug (class 1B anti-arrhytmic like activity as well)
Blocks Na+--inhibits AP's Blocks fast Na+ channels decreases Vmax Antiseizure drug, used occasionally in digitalis OD to reverse AV block SE: Nystagmus, diplopia, ataxia, hirsutism, gingival hyperplasia, Drug induced SLE |
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Mexiletine
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similar to lidocaine except orally active
Mexiletine is approved for treating ventricular arrhythmias |
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Class 1 C
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markedly decreased Vmax due to blockage of fast Na+ channels (His-Purkinje tissue)
No effect on APD No ANS effects Flecainide Encainade-no longer available Propafenone |
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Flecainide
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Class 1 C
blocks Na+ current and delayed rectifier K+ current very long recovery from Na+ channel block approved for the maintenance of sinus rhythm in patients with supraventricular arrhythmias, including atrial fibrillation, in whom structural heart disease is absent SE: increased mortality in patients convalescing from MI, heart block, arrhytmias, CHF worsens |
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Class 2
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Beta Blockers
decreases SA/AV activity by removing SANS stimulus Decreased slope of phase 4 (diastolic currents of AP pacemakers) Use: Post MI prophylaxis (e.g. Metoprolol), SVT's |
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Class 3
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K+ channel blockers (delayed rectifier current)
Increased APD and ERP, especially in Purkinje and Ventricular tissues |
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Amiodarone
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Has activity of all classes (class 1-4)
Blocks inactivated Na+ channels,beta adrenergics, K+ rectifier and Ca2+ channels increased APD and ERF in all cardiac tissues T1/2 30-60 days structural analog of thyroid hormone SE: (chronic therapy) Pulmonary fibrosis, corneal deposits, smurf skin, phototoxicity,neuropathy, thyroid hyper/hypofunction, torsades, hepatic necrosis and increased LDL |
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Sotolol
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Class 3 (K+ & Beta1 block)
two enantionmers--both increase APD and ERP due to K+ channel block one acts as a Beta 1 blocker to decrease HR and AV conduction SE: Lassitude, impotence, depression, torsades, AV block |
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Class 4
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Ca2+ channel blockers
decrease SA and AV pacemaker activity Decreased slope 4 in pacemakers SE:GI distress, GERD,polyuria/nocturia,gingival enlargement (44% Nifedipine), dizziness, flushing, hypotension, AV block, inhibition of CYP3A4 CHF-don't use together w/ beta blockers |
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Verapamil
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Class 4
Ca2+ blocker Cardioselective-but also block vascular Ca2+-hypotension & reflex tachy Use: Prophylaxis in reentrant nodal and atrial tachy (not for WPW), avoid in VT, interaction w/ Digitalis |
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Diltiazem
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Class 4 Ca2+ blocker
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Nifedipine
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Class 4 Ca2+ blocker
most potent, no AV block |
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Adenosine
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Class X
Decrease in SA/AV activity and AV nodal refractory period Activates A receptors--causes Gi coupled decrease in cAMP--K+ efflux causes membrane hyperpolarization Use: PSVTs and AV nodal arrhytmias (stops AV node ~less than 5 sec to reset) IV T1/2 less than 30 sec SE: Flushing, sedation, dyspnea, bronchospasm (rare), a-fib (rare). Antagonized by Theophylline |
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Treatment of Torsades
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Correct hypomagnesimia
Discontinue drugs that prolong QT Try to shorten APD with drugs (e.g. isoproterenol--Beta agaonist) or electrical pacing |
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Drugs that prolong QT
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Prolonged QT--torsades
(>450 ms in men, >470 ms in women; normal less or equal to 430) (blockers of K+, also w/ enhanced inward Na+) Quinidine Ibultide Sotolol Procainamide Disopyramide Dofelitide Ibultilde Amiodorone (rare) Non-cardiac drugs Azole anti-fungals Cisapride (5-HT4 agonist--IBS) Haloperidol Thioridazine Ziprasidone Tricyclic Antidepressants |