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What are examples of class IV antiarrhythmic drugs (2)?
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Why is it important that calcium channel blockers must be given with caution to patients recieving B-blocker therapy?
Negative inotropic action of B-blocker => atrioventricular block
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Digoxin is generally effective for controlling ventricular rate in dogs and cats with what, because of its anti-adrenergic action at AV junction?
Atrial tachyarrhythmias
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If cocomitant use of anti-arrhythmic drugs is used for increased effectiveness, then the drug interactiong should be considered, it can be of what?
- Pharmacodynamic interaction or
- Pharmacokinetic interaction
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What drug decreased the max rate of phase 0 depolarization of cardiac cells, and produces a direct depressant effect on Na+ permeability or the relationship between resting membrane potential and NA+ conductance?
Quinidine sulphate
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The capability of quinidine to directly prolong the refractory period of atrial fibers helps in what?
Converting atrial fibrillation to sinus rhythm
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What are the 2 ways that Qunidine acts?
- Directly: Prolong the refractory period
- Indirectly: Lengthens refractory period (anticholinergic action)
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The vagolytic activity of quinidine induces improved what?
AV conduction
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What is the clinical used of quinidine (3)?
- Ventricular premature complexes
- Ventricular tachycardia
- Maintenance after electroconversion of Atrial fibrillation/flutter
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Why is quinidine not recommended in AV block or interventricular block?
Anticholinergic effect on AV node
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Procainamide is more effective in controlling ____ than ____?
Ventricular arrhythmias than Atrial arrhythmias
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What drug is classified as a "local anaesthetic type" is considered as effective in controlling digitalis-induced arrhythmias and for the treatment of ventricular arrhythmias?
Phenytoin
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Dogs recieving phenytoin tend to develop phenytoin toxicosis when what drug is given?
- Chlorampehnicol
- (inhibits the metabolism of phenytoin)
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Why does lidocain hydrochloride have a limited use for maintenance therapy?
- Inefficient PO absorption
- Short duration of action
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What drug slows the rate of spontaneous discharge of the SA and ectopic pacemakers and slows both antegrade and retrograde conduction through anomalous pathways of the heart?
Propanolol
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Propanolol and other B-blockers are effective for the control of what?
Arrhythmias during inhalation anarsthesia with halogenated hydrocarbon anaesthetics
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Why is propranolol not recommended to use in animals with chronic obstructive airway disease?
- It is a non-selective B-blocker
- B2 receptor causes airway obstruction
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Propanolol and other B-blockers are used cautiously in patients with reduced cardiac reserve (CHF) because?
Sympathetic activity is more pronounced in these patients to maintain cardiac output
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Arrhythmias caused by disturbances in either impulse formation or impulse conduction are controlled by what drug?
Verapamil
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Adverse effects of calcium channel blockers are decreased contractile response of the heart, reduced cardiac output, and hypotension. This results in what (3)?
- Cardiac decompensation in heart failure patients
- Induces pulmonary edema
- Worsening of condition
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What drug is an adrenergic neuronal blocking agent since it inhibits release of norepinephrine from adrenergic nerve endings, prolongs the action potential as well as refractory period in ventricular muscle cells?
Bretylium
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Since bretylium initially causes a release of catecholamines prior to neuronal blockade, what is produced as an effect secondary to catecholamine release?
Ventricular arrhythmias
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What has a pronounced atropine-like side effects, so it increases ventricular rate in patients with atrial fibrillation or flutter?
Disopyramide
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What are advantages of tocainide?
- Effective after oral administration
- Long duration of action
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The structural modification of tocainide from lidocain prevents what?
- Rapid first-pass hepatic metabolism
- Improves bioavailability
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What drug is considered an alternative strategy for controlling ventricular arrhytmias in dogs resistant to standard anti-arrhythmic therapy?
Aprinidine
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What are class IC antiarrhythmic drugs which blocks the Na+ conductance as that as that of quinidine, but it does nto cause the prolonged refractory period (3)?
- Encainide
- Flecainide
- Lorcainide
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What drug is used at low concentration along with local anesthetics, lidocaine hydrochloride, it extends the duration of local anaesthetics 2 fold?
Epinephrine
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When should epinephrine not be used?
- Acute left ventricular failure
- Cardiac emergencies during anaesthesia
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What is it called when epinephrine is administered to an animal with blocked a1-adrenoceptors results in a depressor rather than a pressor response?
Epinephrine reversal
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What drug produces dilation of skeletal muscle vascular beds and relaxation of bronchial smooth muscle (B2 mediated action)?
Isoproterenol
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What are the clinical indications of isoproterenol?
Short term emergency management of partial or complete heart block, cardiac arrest
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What drug is the immediate precursor of norepinephrine, causes vasodilation, at intermediate infusion rates, it stimulates B1 adrenoceptors in the heart producing a positive inotropic action in addition to decreased peripheral vascular resistance?
Dopamine
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The increased cardiac output increased renal blood flow, thus dopamine can be used for what?
Adjunctive therapy for oliguric renal failure
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What plan contains a cardenolide which causes cardiac toxicity in liverstock?
Oleander
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