Anti-Arrhythmic Drugs Lecture Notes

Overview of Anti-Arrhythmic Classes

• Class 1: Sodium Channel Blockers
• Class 2: Beta Blockers
• Class 3: Potassium Channel Blockers
• Class 4: Calcium Channel Blockers

Learning Approach

• Avoid memorizing charts; use mnemonics instead.
• Focus on how medications alter the cardiac action potential and their main adverse drug reactions.

Class 1: Sodium Channel Blockers (1C, 1A, 1B)

• Framework: Use mnemonic "Salty CAB driver" (C = 1C, A = 1A, B = 1B)
  • 1C (CAB): Flecainide, Propafenone
    • Decrease phase 0 slope the most.
    • ADR: Contraindicated post-MI (C for Contraindicated)
  • 1A: Quinidine, Dysopyramide, Procainamide
    • Intermediate decrease in phase 0 slope.
    • ADR:
      • Quinidine: Cinchonism (headache, tinnitus)
      • Procainamide: Drug-induced lupus
      • All 1A agents: Torsades de Pointes
  • 1B: Mexiletine, Lidocaine
    • Least decrease in phase 0 slope.
    • ADR: Best post-MI (B for Best)

Class 2: Beta Blockers

• Mechanism: Decrease slope of phase 4 depolarization
• Mnemonic: Beta has 4 letters (SA/AV = 4 letters, OLOL = 4 letters, A-fib = 4 letters)
• Examples: Propranolol, Metoprolol, Esmolol, Atenolol
• ADR: COPD exacerbation, impotence, hypoglycemic masking

Class 3: Potassium Channel Blockers

• Examples: Amiodarone, Ibutilide, Dofetilide, Sotalol (mnemonic: AIDS)
• Mechanism: Prolong phase 3 repolarization
• Mnemonic: Draw "P" for prolonged phase 3
• ADR:
  • Torsades de Pointes (TDP = 3 letters)
  • Amiodarone: Check PFTs, LFTs, TFTs (3 letters each)

Class 4: Calcium Channel Blockers

• Examples: Verapamil, Diltiazem
• Mechanism: Decrease slope of phases 0, 3, and 4 (0+3+4 = 7; Calcium has 7 letters)
• ADR: Lower extremity edema, constipation

Important Notes

• Be able to draw and explain how each class affects the cardiac action potential.
• Focus on high-yield ADRs, especially for class 1 agents and amiodarone.

Summary Chart

• Class 1: Sodium Channel Blockers
  • Mechanism: Decrease phase 0 slope.
  • ADRs: Contraindicated post-MI (1C), Torsades (1A), Best post-MI (1B)
• Class 2: Beta Blockers
  • Mechanism: Decrease phase 4 slope.
  • ADRs: Exacerbate COPD, impotence, mask hypoglycemia.
• Class 3: Potassium Channel Blockers
  • Mechanism: Prolong phase 3.
  • ADRs: TDP, amiodarone toxicity (lungs, liver, thyroid).
• Class 4: Calcium Channel Blockers
  • Mechanism: Decrease slopes of phases 0, 3, and 4.
  • ADRs: Edema, constipation.

By organizing information with mnemonics and focusing on mechanisms and ADRs, students can better retain and understand the complex topic of anti-arrhythmic drugs.