Class IV Antiarrhythmic Drugs Overview

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Questions and Answers

Which of the following are considered Class IV antiarrhythmic drugs?

Diltiazem (correct)

Propranolol

Verapamil (correct)

Atenolol

What mechanism do Class IV antiarrhythmic drugs primarily use to impact cardiac cells?

Inhibit adrenergic receptors

Block sodium channels

Block slow inward calcium current (correct)

Increase potassium efflux

What is a common side effect associated with the use of verapamil?

Paralysis

Insomnia

Nausea

Constipation (correct)

Which of the following conditions is a contraindication for administering diltiazem?

2nd or 3rd degree heart block Signup and view all the answers

What is the effect of calcium channel blockers like diltiazem and verapamil on the AV node?

Decrease AV conduction Signup and view all the answers

What should be considered when dosing verapamil in patients with liver disease?

Reduce the dose requirement Signup and view all the answers

What type of arrhythmias is diltiazem particularly effective against?

Atrial fibrillation/flutter Signup and view all the answers

Which drug interaction is a significant concern for both diltiazem and verapamil?

Inhibition of 3A4 metabolism Signup and view all the answers

Which of the following can be a serious side effect of diltiazem?

Congestive heart failure Signup and view all the answers

How does the administration of grapefruit juice affect verapamil?

Inhibits its metabolism Signup and view all the answers

What effect does the administration of calcium channel blockers like diltiazem and verapamil have on physiological parameters of the heart?

Prolongs the refractory period in the AV node and atria Signup and view all the answers

Which of the following best describes a key safety precaution to consider when using diltiazem?

Monitor for bradycardia and AV block Signup and view all the answers

What is the primary biochemical action of Class IV antiarrhythmic drugs?

Selectively block the slow inward current carried by calcium Signup and view all the answers

In which condition is verapamil contraindicated?

2nd or 3rd degree heart block Signup and view all the answers

Which drug interaction is particularly concerning with both diltiazem and verapamil?

Inhibition of metabolism of many 3A4 drugs Signup and view all the answers

What is a common side effect experienced by patients taking verapamil?

Dizziness Signup and view all the answers

What specific patient condition may necessitate a reduced dose of diltiazem?

Severe liver disease Signup and view all the answers

What type of heart rhythm condition is diltiazem indicated for?

Paroxysmal supraventricular tachycardia (PSVT) Signup and view all the answers

What effect do calcium channel blockers have on systemic vascular resistance?

Decrease systemic vascular resistance Signup and view all the answers

What is the bioavailability range of verapamil?

13-65% Signup and view all the answers

Study Notes

Class IV Antiarrhythmic Drugs

Class IV antiarrhythmics include diltiazem and verapamil, both calcium channel blockers.
They selectively block the slow inward current carried by calcium.
The slow inward current is crucial for the normal action potential in SA node cells.
This current is also suggested to be involved in the genesis of certain cardiac arrhythmias.
Class IV antiarrhythmics prolong the refractory period in the AV node and atria.
They also decrease AV conduction and spontaneous diastolic depolarization.
Verapamil is available in intravenous (IV) and oral (PO) formulations.
Verapamil is used for treating atrial fibrillation/flutter, PSVT, hypertension, and angina.
Verapamil also decreases systemic vascular resistance (SVR) and pulmonary vascular resistance (PVR).
Verapamil has a bioavailability of 13-65% and is metabolized by hepatic P450.
Verapamil is contraindicated in cardiogenic shock, 2nd or 3rd degree heart block, severe LV dysfunction, and hypotension.
Verapamil can exacerbate CHF and should be avoided with negative chronotropes and inotropes.
Common side effects of verapamil include constipation, headache, dizziness, edema, and hypotension.
Serious side effects of verapamil include heart block and CHF.
Verapamil interacts with grapefruit juice and many 3A4 drugs including dofetilide, simvastatin, and digoxin.
Simvastatin dosage should be limited to 10 mg when co-administered with verapamil.
Oral bioavailability of verapamil varies between extended-release products.
Diltiazem is available in IV and PO formulations.
Diltiazem is used for treating atrial arrhythmias, hypertension, PSVT, and stable angina.
Diltiazem also decreases SVR (PVR).
Diltiazem has a bioavailability of 40% for regular release and variable bioavailability for extended-release products.
Diltiazem is metabolized by hepatic 3A4.
Diltiazem is contraindicated in AMI with pulmonary congestion, cardiogenic shock, 2nd or 3rd degree heart block, and ventricular tachycardia.
Diltiazem can exacerbate CHF and should be avoided with negative chronotropes and inotropes.
Common side effects of diltiazem include bradycardia, peripheral edema, dizziness, headache, fatigue, and constipation.
Serious side effects of diltiazem include CHF, AV block, and hepatotoxicity.
Diltiazem interacts with many 3A4 drugs including simvastatin and QT prolonging drugs.
Simvastatin dosage should be limited to 10 mg when co-administered with diltiazem.
Oral bioavailability of diltiazem varies between extended-release products and may be impacted by food.
Diltiazem can be given as an IV bolus or a continuous infusion for acute rhythm control.

Class IV Antiarrhythmics

Class IV antiarrhythmics are calcium channel blockers, specifically diltiazem and verapamil.
They selectively block the slow inward current carried by calcium in cardiac cells.
This slow inward current plays a role in the normal action potential in SA node cells and is implicated in the genesis of certain cardiac arrhythmias.
These drugs prolong the refractory period in the AV node and atria, decrease AV conduction, and reduce spontaneous diastolic depolarization.

Verapamil (Calan, Isoptin®)

Available in intravenous (IV) and oral (PO) formulations.
Used for atrial fibrillation/flutter, paroxysmal supraventricular tachycardia (PSVT), hypertension, and angina.
Off-label uses include migraine.
Decreases systemic vascular resistance (SVR) and pulmonary vascular resistance (PVR).
Bioavailability ranges from 13-65%.
Metabolized by hepatic P450 enzymes, requiring dose reduction in severe liver disease.
Contraindicated in cardiogenic shock, 2nd or 3rd degree heart block, severe left ventricular (LV) dysfunction, and hypotension.
Precautions include exacerbation of congestive heart failure (CHF) and avoidance of negative chronotropes and inotropes.
Common adverse effects include constipation, headache, dizziness, edema, and hypotension.
Serious adverse effects can include heart block and CHF.
Interacts with grapefruit juice and many other drugs metabolized by CYP3A4, increasing levels of drugs like dofetilide, simvastatin, and digoxin.
Dosing of simvastatin should be limited to 10 mg when combined with verapamil, with verapamil limited to 240 mg.
Oral bioavailability varies between extended-release products.

Diltiazem (Cardizem®)

Available in IV and PO formulations.
Used for atrial arrhythmias, hypertension, PSVT, and stable angina.
Off-label uses include unstable angina.
Also decreases SVR and PVR.
Bioavailability is 40% for regular release formulations, with wider variability for extended-release products.
Metabolized by hepatic CYP3A4 enzymes, requiring dose reduction in severe liver disease.
Contraindicated in acute myocardial infarction (AMI) with pulmonary congestion, cardiogenic shock, 2nd or 3rd degree heart block, and ventricular tachycardia.
Precautions include CHF exacerbation and avoidance of negative chronotropes and inotropes.
Common adverse effects: bradycardia, peripheral edema, dizziness, headache, fatigue, and constipation.
Serious adverse effects can include CHF, AV block, and hepatotoxicity.
Interacts with many drugs metabolized by CYP3A4, increasing levels of drugs like simvastatin and QT-prolonging drugs.
Can be given as an IV bolus or continuous infusion for acute rhythm control.
Dosing of simvastatin should be limited to 10 mg when combined with diltiazem, with diltiazem limited to 240 mg.
Oral bioavailability varies between extended-release products and can be affected by food.

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Description

This quiz covers Class IV antiarrhythmic drugs such as diltiazem and verapamil, focusing on their mechanisms, uses, and effects on cardiac electrophysiology. Test your understanding of how these calcium channel blockers operate in the management of various cardiac conditions, including atrial fibrillation and hypertension.