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Pharmacology > Antidysrythmic Drugs > Flashcards

Antidysrythmic Drugs Flashcards

1
Q

What is atrial fibrilation?

A

a chaotic rhythm of the QRS complexes

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2
Q

What is shown here?

A

an illustration of a damaged pathway

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3
Q

What is shown here?

A

Depolarization struggles to get through the muscle, but does, the P-QRS complex is just bigger

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4
Q

What is shown here?

A

re-entry

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5
Q

What is shown here?

A

Depolarization struggles to get around, but keeps going around in circles: re-entry arrhythmias

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6
Q

What do class I antidysrhythmic drugs do?

A

block voltage-sensitive Na channels

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7
Q

What do class II antidysrhythmic drugs do?

A

beta adrenoceptor antagonists (beta blockers)

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8
Q

What do class III antidysrhythmic drugs do?

A

They prolong the refractory period of the myocardium - increase the refractory period gap

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9
Q

What do class IV antidysrhythmic drugs do?

A

Calcium antagonists - impair impulse propagation in damaged areas of the myocardium and dilate coronary arteries

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10
Q

How do class I antidysrhythmic drugs work?

A

they block Na channels in the open or refractory stage (in depolarized/damaged muscle) and inhibit the refractory stage

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11
Q

When do class I antidysrhythmic drugs have the greatest efficacy?

A

when the heart is beating rapidly

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12
Q

What drug is a class Ib antidysrhythmic drug?

A

lidocaine

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13
Q

Class Ib antidysrhythmic drugs _______ and _______ rapidly.

A

associate, dissociate

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14
Q

What are class Ib antidysrhythmic drugs useful for?

A

the control of ventricular dysrhythmias after myocardial infarction

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15
Q

What drug is a class Ic antidysrhythmic drug?

A

flecainide

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16
Q

Class Ic associate and dissociate more ____.

A

slowly

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17
Q

Since class Ic drugs associate and dissociate more slowly what does that say about their steady state block level?

A

it does not vary with the stage of the cycle

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18
Q

What are class Ic drugs used for?

A

general reduction in excitation and have less effect against premature beats like class Ib

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19
Q

What will class Ic drugs suppress?

A

re-entrant rhythms

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20
Q

What drugs are class 1a antidysrhythmic drugs?

A

Procainamide and Quinidine

21
Q

How do muscarinic receptors affect the heart?

A

they decrease heart rate and excitability

22
Q

What drug is a class II antidysrhythmic drug?

A

propanolol - beta antagonist

23
Q

What are class II antidysrhythmic drugs used to do?

A

reduce excitability due to sympathetic over-activity and reduce AV conduction in atrial tachycardias to slow ventricular rate

24
Q

Why would you want to use propranolol in cats with thyroid hyperplasia?

A

because thyroid hyperplasia can cause arythmias

25
Q

What is the main class III antidysrhythmic drug?

A

amiodarone

26
Q

What is the special feature of class III antidysrhythmic effects?

A

they prolong the cardiac action potential and increase refractory period

27
Q

What effects does Class III antidysrhythmic drugs have?

A

it produces ventricular and supra-ventricular antidysrhythmic effects - complex mechanism including K channel block and calcium channel block

28
Q

What are the main examples of class IV antidysrhythmic drugs?

A

Verapamil and diltiazem

29
Q

What do class IV antidysrhythmic drugs do?

A

they block sensitive Ca channels which inhibits transient inward current and thus suppressing premature ectopic beats and re-entrant rhythms

30
Q

What do class IV antidysrhythmic drugs do to the plateau phase of the action potential?

A

it is shortened

31
Q

What is the effect of Class IV antidysrhythmic drugs on the coronary arteries?

A

it dilates them

32
Q

What is procainamide?

A

a class 1a antidysrhythmic drug

33
Q

When is procainamide indicated?

A

in dogs for maintenance of ventricular arrhythmias or ventricular tachycardia In humans - Torsades de points

34
Q

When is Procainamide contraindicated?

A

in dogs with conduction block

35
Q

When is lidoocain used?

A

without epinephrine intravenously for severe acute ventricular arrhythmias of any cause

36
Q

Why isn’t lidocaine given orall?

A

because of the efficient first pass effect through the liver

37
Q

When should you reduce doses of lidocaine?

A

in congestive heart failure or hepatic disease

38
Q

What does propranolol prevent?

A

reflex tachycardia

39
Q

What does propranolol reduce?

A

blood pressure and ventricular hypertrophy in cardiomyopathy associated with hyperthyroidism

40
Q

What is a possible side effect of propanolol use?

A

bronchial muscle spasm

41
Q

What does amiodarone do?

A

prolongs the refractory period of cardiac action potential

42
Q

What amiodarone used for?

A

treatment of supra-ventricular and ventricular arrhythmias

43
Q

What side effects are associated with amiodarone?

A

pulmonary fibrosis, gastro-intestinal disturbances, corneal deposits

44
Q

What is the half-life with amiodarone?

A

long elimination half-life

45
Q

What type of drugs are Verapamil and Diltiazem?

A

class IV antidysrhythmic

46
Q

How do Verapamil and Diltiazem work?

A

they inhibit slow Ca channels and dilate capillaries

47
Q

What conditions are Verapamil and Diltiazem favored for?

A

supraventricular tachycardias

48
Q

How is Verapamil favored to be given?

A

IV

49
Q

How is Diltiazem favored to be given?

A

long-term oral administration

Pharmacology (16 decks)

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