Pharmacology Lecture 8: Antiarrhythmic Drugs

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What is the primary mechanism of action of antiarrhythmic drugs?

They directly stimulate the sympathetic nervous system.

They enhance the heart's contraction strength.

They normalize the conductivity of electrolytes through ion channels. (correct)

They increase heart rate.

Which class of antiarrhythmic drugs primarily blocks sodium channels?

Class I (correct)

Class II

Class IV

Class III

What side effect can result from large doses of Quinidine?

Nausea

Rapid heart rate

Elevated blood pressure

Blurred vision (correct)

Which medication is classified as a Class IB antiarrhythmic agent?

Lidocaine Signup and view all the answers

What therapeutic use is Quinidine primarily indicated for?

Treatment of a wide range of arrhythmias Signup and view all the answers

How is Lidocaine typically administered, and why?

Intravenously, due to first-pass metabolism. Signup and view all the answers

What happens when antiarrhythmic drugs close damaged ion channels?

They reduce the negative impact on the heart. Signup and view all the answers

Which of the following ions is primarily involved in the action potential of cardiomyocytes?

Sodium (Na+) Signup and view all the answers

What is a common side effect of mexiletine?

Dyspepsia Signup and view all the answers

Which of the following is NOT a therapeutic use of flecainide?

Atrial fibrillation Signup and view all the answers

What is the primary mechanism of action for Class II antiarrhythmic drugs?

Block beta-adrenergic receptors Signup and view all the answers

What distinguishes esmolol from other beta-blockers?

It has a rapid onset of action Signup and view all the answers

Which class of antiarrhythmic drugs is known to block potassium channels?

Class III Signup and view all the answers

What is a requirement for dosing lidocaine in patients receiving beta-blockers?

Dose adjustment due to reduced blood flow Signup and view all the answers

What is a significant side effect associated with amiodarone?

Pulmonary fibrosis Signup and view all the answers

What is the typical absorption characteristic of amiodarone?

Not fully absorbed after administration Signup and view all the answers

Study Notes

Course Information

Institution: Asian Medical Institute Memorial S. Tentishev
Department: Interprofessional Discipline
Subject: Basic and clinical Pharmacology
Teacher: Temirbekova Gulnura
Lecture: No. 8
Theme: Antiarrhythmic drugs

Arrhythmia

Arrhythmia is a disruption of cardiac conduction, frequency, and regularity of contractions, leading to abnormal heart function and unpleasant symptoms.
Arrhythmias are changes in heart function that disrupt proper contraction, impacting both speed and synchronicity.

Mechanism of Action of Antiarrhythmic Drugs

Antiarrhythmic drugs aim to normalize electrolyte conductivity through myocardial ion channels.
Cardiomyocytes have numerous ion channels along which potassium, sodium, and chlorine ions move.
This ion movement creates action potentials in each cell, facilitating nerve impulse conduction.

Correcting Ion Movement

To fix disturbed ion movement, antiarrhythmic drugs reduce activity and stop the impulse cycle.
These drugs achieve this by closing damaged ion channels and minimizing negative impacts on the heart and sympathetic receptors.

Class I Antiarrhythmic Drugs

Class IA: Quinidine
- Mechanism: Blocks open sodium channels, preventing sodium influx.
- Therapeutic use: Treats various arrhythmias, including atrial fibrillation.
- Pharmacokinetics: Rapid and complete oral absorption with extensive liver metabolism.
- Side effects: High doses can lead to blurred vision, tinnitus, headaches, disorientation, and psychosis.
Class IB: Lidocaine and Mexiletine
- Mechanism: Quick binding and dissociation with sodium channels.
- Pharmacokinetics: Lidocaine is given intravenously due to liver metabolism preventing oral administration.
  - Drugs inhibiting liver function (e.g., beta-blockers) may require lidocaine dose adjustment. Mexiletine is easily absorbed orally.
- Side effects: Nausea, vomiting, and dyspepsia are typical side effects.
Class IC: Flecainide and propafenone
- Mechanism: Blocks potassium channels, increasing action potential duration.
- Effects: Active even at normal heart rate.
- Therapeutic use: For maintaining sinus rhythm and in specific types of arrhythmias.
- Pharmacokinetics: Oral absorption, with potential dosage adjustments in renal failure.
- Side effects: Often well-tolerated; dizziness and nausea are common.

Class II Antiarrhythmic Drugs

β-blockers: Prevent life-threatening ventricular arrhythmias (e.g., after myocardial infarction).
Metoprolol: Commonly used to treat cardiac arrhythmias, extensively metabolized by the liver.
Esmolol: Very short-acting β-blocker, ideal for managing emergency arrhythmias, administered intravenously.

Class III Antiarrhythmic Drugs

Potassium channel blockers (e.g., Amiodarone): Effective against refractory supraventricular and ventricular tachyarrhythmias.
Amiodarone: Used to manage fibrillation or atrial flutter.
Pharmacokinetics: Long duration of action, distributed in adipose tissue, and requires several months to achieve full effect.
Side effects: Potential for various toxic effects, including pulmonary fibrosis, neuropathy, and hepatotoxicity; careful monitoring and controlled dosage are crucial.
Sotalol: Acts as both a class III agent and a non-selective beta-blocker. Used for maintaining a normal sinus rhythm in atrial fibrillation, typically in those needing preventative treatment in cases of left ventricular hypertrophy or atherosclerotic heart disease.

Class IV Antiarrhythmic Drugs

Calcium channel blockers (e.g., Verapamil): Primarily affect smooth muscle of blood vessels and the heart.
Verapamil: Has greater impact on the heart and is more effective for atrial than ventricular arrhythmias.

Other Antiarrhythmic Drugs

Magnesium sulfate: Used intravenously to manage arrhythmias because oral magnesium is ineffective for arrhythmia treatment. Necessary for sodium, calcium, and potassium transport through cell membranes.

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Description

This quiz covers Lecture No. 8 on Antiarrhythmic drugs from the Basic and Clinical Pharmacology course. You will explore the mechanisms of action for these drugs and their impact on cardiac conduction and rhythm. Prepare to test your understanding of how these medications restore normal heart function.