Lidocaine is effective in suppressing ischemic ventricular arrhythmias because it exhibits use dependence. Which property best explains this phenomenon?
- A It prolongs the action potential duration
- B It blocks sodium channels preferentially in the open or inactivated state ✓
- C It blocks potassium channels during phase 3
- D It decreases automaticity in the SA node
Correct answer: B. It blocks sodium channels preferentially in the open or inactivated state
Explanation
Use dependence means a drug blocks sodium channels more effectively when they are frequently opening and closing, as occurs during rapid rates or ischemia. Lidocaine binds to open and inactivated Na+ channels, dissociating during diastole. This selectively suppresses rapidly firing ischemic ventricular tissue without significantly affecting normal rhythm.
Reference: Katzung Basic and Clinical Pharmacology, 15th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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