Class 1B Anti-arrhythmics

Question 1

Class 1 Anti-arrhythmics are also known as what?

Answer 1

Na+ channel blockers

Question 2

Class 1B anti-arrhythmics ______ action potential.

Answer 2

Shortens

Question 3

Name 3 drugs that falls under the class 1B anti-arrhythmic category?

Answer 3

1. Lidocaine
2. Phenytoin
3. Mexiletine

Question 4

Out of the 3 drugs listed in this category, what is the drug of choice to treat ventricular tachycardia and ventricular arrhythmias in dogs?

Answer 4

Lidocaine

Question 5

Why can Lidocaine not be given orally?

Answer 5

Undergoes significant 1st pass effect.

Question 6

What drug is given in place of Lidocaine orally?

Answer 6

Mexiletine

Question 7

When giving Lidocaine IV you must give it over what amount of time?

Answer 7

2 minutes because if it is given too quickly you can get CNS signs.

Question 8

Initially in cats when treating VPCs you will give Propranolol/Atenolol (Beta blockers) but as a 2nd choice you would give this drug.

Answer 8

Lidocaine (low dose boluses or as a CRI)

Question 9

In an ER with a dog showing VPCs on an EKG what would your first choice drug be?

Answer 9

Lidocaine as boluses or a CRI.

Question 10

In a non-emergency or when an animal is stable how would you treat VPCs in a dog?

Answer 10

You could use Mexiletine + a beta blocker (like Sotalol).

Question 11

Can Mexiletine be used to treat VPCs in a stable cat?

Answer 11

Yes, but it wouldn’t be your first choice. Your first choice would be oral Propranolol/Atenolol.