Group 3: Potassium Channel Blockers – Antiarrhythmic Drugs

by Pravin Shukle, MD

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    The group 3 antiarrhythmics are quite complex, but they are actually a lot of fun to use, a lot of fun to administer, and a lot of fun to learn about. So these are potassium channel blocker active agents. These channels are responsible for repolarizing the membrane. Now, it includes medications that "cross" into other classes as I mentioned before. It prolongs the action potential and it also increases the QT interval on the electrocardiogram. The most important thing that I want you to remember is that this drug increases the effective refractory period. And that reduces the response to atrial tachycardia. Now, the classic drugs in the group 3 is ibutilide, prototypical drugs. Now, sotalol is a beta blocker but it's also a class 3 antiarrhythmics. It's a chiral mixture of two different types of sotalol. So, chiral means mirror image. So for example, my left hand is a chiral image of my right hand. Amiodarone and dronedarone are now new class 3 antiarrhythmic drugs. In fact, amiodarone is probably the most commonly used antiarrhythmic today. And I would argue that it is the most effective antiarrhythmic out there. It blocks the potassium current, as well as the sodium and calcium current. And it also has some beta blocking ability. So, you can see that drugs in this class cross classes. They are hard to classify, but let's leave it in the group 3 drugs. I want to talk specifically about amiodarone for a moment because you're going to encounter these patients on amiodarone all the time, and it's going to be a big part of the pharmacology cardiology lectures, and it's going to be a big part of your exam. So, toxicity is important to know. One of the things that we see with amiodarone toxicity is pulmonary...

    About the Lecture

    The lecture Group 3: Potassium Channel Blockers – Antiarrhythmic Drugs by Pravin Shukle, MD is from the course Cardiovascular Pharmacology.

    Included Quiz Questions

    1. ...act on the potassium channels, which affect depolarization of the membrane.
    2. ...will shorten the action potential.
    3. ...will shorten the PR interval on the ECG.
    4. ...will shorten the effective refractory period (ERP)
    5. ...increases the ventricular response to atrial dysrhythmia and tachycardia.
    1. ...Amiodarone and Sotalol.
    2. ...Amiodarone and Esmolol.
    3. ...Esmolol and Sotalol.
    1. ...blocks the slow sodium, potassium, and calcium currents, and has beta blocking ability.
    2. ...blocks the slow sodium current.
    3. ...blocks the slow sodium, potassium, and calcium currents.
    4. ...has beta blocking ability.
    1. The crackles are due to fibrosis. Consider pulmonary fibrosis secondary from Amiodarone toxicity.
    2. The crackles are due to pulmonary oedema. Consider heart failure due to excessive beta blockade
    3. The crackles are due to blood in the lung. Consider pulmonary hemorrhage due to the dabigitran.
    4. The crackles are due to air trapping. Consider emphysema due to smoking.
    1. Hepatic steatosis
    2. Corneal verticillata
    3. Microcrystalline deposits causing pulmonary fibrosis
    4. Parasthesia and tremor due to peripheral neuropathy
    5. Tremor due to thyroid dysfunction (hyperthyroidism), or alternatively hypothyroidism

    Author of lecture Group 3: Potassium Channel Blockers – Antiarrhythmic Drugs

     Pravin Shukle, MD

    Pravin Shukle, MD

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