Anti-dysrhythmics

Question 1

What is the mechanism of action of the Class I anti-dysrhythmic drugs?

Answer 1

Block voltage-sensitive sodium channels

Question 2

What is the mechanism of action of the Class II anti-dysrhythmic drugs?

Answer 2

Beta adrenoreceptor antagonists

Question 3

What is the mechanism of action of the Class III anti-dysrhythmic drugs?

Answer 3

Prolong the refractory period of the myocardium, suppress re-entrant rhythms.

Question 4

What is the mechanism of action of the Class IV anti-dysrhythmic drugs?

Answer 4

Calcium antagonists - impair impulse propagation in damaged areas of the myocardium.

Question 5

Class I drugs bind most strongly when Na+ channels are in the ____ or ____ state.

Answer 5

Open or refractory

Question 6

Class I drugs are _____ dependent.

Answer 6

Frequency

Question 7

Class I drugs work better at (high or low) frequencies?

Answer 7

High

Question 8

Which drug is a Class Ib anti-dysrhthmic?

Answer 8

Lidocaine

Question 9

For what type of condition would a Class Ib be used?

Answer 9

Ventricular dysrhythmia following myocardial infarction

Question 10

Which drug is a Class Ic anti-dysrhythmic?

Answer 10

Flecainide

Question 11

For what are Class Ic drugs used?

Answer 11

General reduction of excitation (dampen excitability of the heart)

Question 12

Which two drugs are Class Ia anti-dysrhythmics?

Answer 12

1. Quinidine

2. Procainamide

Question 13

Place the following in order of slowest to faster to associate and dissociate: Class Ia, Class Ib, Class Ic.

Answer 13

Class Ic

Question 14

Beta-1 receptors on the heart increase ____ ____ and ____.

Answer 14

Beta-1 receptors on the heart increase HEART RATE and EXCITABILITY.

Question 15

Which drug is used as an example of the Class III anti-dysrhythmics?

Answer 15

Amiodarone

Question 16

What are the two drugs used as examples for the Class IV anti-dysrhythmics?

Answer 16

1. Verapamil

2. Diltiazem

Question 17

For what is Quinidine used in the horse?

Answer 17

Atrial fibrillation (prolongs the atrial refractory period)

Question 18

What are the main indications for the use of Quinidine?

Answer 18

Atrial and ventricular dysrhythmias (tachycardias)

Question 19

What is the contraindication for the use of Quinidine?

Answer 19

Hepatic insufficiency

Question 20

What are the side effects associated with Quinidine? (There are 7)

Answer 20

1. Anorexia
2. Diarrhea
3. Vomiting
4. Ventricular fibrillation
5. Tachycardia
6. Ataxia
7. Allergic reaction

Question 21

How is Quinidine administered?

Answer 21

Orally

Question 22

Procainamide is often preferred in the dog for maintenance of ____ ____ or ____ ____.

Answer 22

Procainamide is often preferred in the dog for maintenance of VENTRICULAR ARRHYTHMIAS or VENTRICULAR TACHYCARDIAS.

Question 23

Procainamide is contraindicated in _____ _____.

Answer 23

Procainamide is contraindicated in CONDUCTION BLOCK.

Question 24

What are the contraindications for the use of Lidocaine (Class Ib)?

Answer 24

1. Atrial fibrillation

2. Atrial flutter

Question 25

What are the side effects of Lidocaine (Class Ib)?

Answer 25

1. Seizure

2. Hypotension

Question 26

Which drug is NOT effective in the presence of hypokalemia?

Answer 26

Lidocaine