Class IB

• Introduction 

• Illustrated mechanism of action 

• Examples of Medication Brand Names (with Images)

• Indication

• Side Effects 

• Precautions & Contraindications 

• Monographs

• Reference 

• Introduction 

Class IB antiarrhythmic drugs are used to treat specific types of ventricular arrhythmias, especially those that occur after myocardial infarction. They work by modifying the electrical activity of the heart to restore normal rhythm.

• Illustrated mechanism of action

.Class IB antiarrhythmics block fast voltage-gated sodium (Na⁺) channels in cardiac myocytes, especially in ischemic or depolarized ventricular tissue.

 • They decrease the slope of Phase 0 depolarization in the cardiac action potential.

 • They shorten the action potential duration (APD) and effective refractory period (ERP) in ventricular tissue.

 • These drugs work preferentially on damaged or ischemic tissue, making them effective after myocardial infarction.

 • They have minimal effect on atrial tissues or normal ventricular tissue.

• https://youtu.be/tps2rICiL0w?si=7Q7Qa48zlEwfiZl8

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• Examples of Medication Brand Names

• Lidocaine – Brand: Xylocaine

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•  • Mexiletine – Brand: Mexitil

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• Indication

• Ventricular tachycardia

•  • Ventricular fibrillation

•  • Not typically used for supraventricular arrhythmias

• Side Effects 

• Dizziness

•  • Blurred vision

•  • Tremors

•  • Nausea

•  • In toxic doses: seizures and neurological disturbances

• Precautions & Contraindications 

• Use cautiously in patients with liver disease

•  • Contraindicated in patients with known hypersensitivity to the drug

•  • Neurological monitoring is important when given intravenously (especially with lidocaine)

• Monographs

• Reference

• https://www.thecardiologyadvisor.com/ddi/lidocaine-antiarrhythmic/?

• https://www.ncbi.nlm.nih.gov/books/NBK519045/?

• https://cvpharmacology.com/antiarrhy/sodium-blockers?

• https://www.thecardiologyadvisor.com/ddi/lidocaine-antiarrhythmic/?