Antidysrhythmic Medications Lecture Notes

Overview

Focus on antidysrhythmic medications, specifically cardiac glycosides, and Class I and II antidysrhythmics.

Key Medication: Digoxin
- Used for:
  - Heart failure
  - Atrial fibrillation
  - Atrial flutter
- Mode of Action:
  - Positive inotropic effect: Increases force and efficiency of heart contractions
  - Negative chronotropic effect: Decreases heart rate
- Side Effects:
  - Dysrhythmias (e.g., bradycardia)
  - Digoxin toxicity (watch for GI upset, fatigue, weakness, vision issues)
- Monitoring:
  - Check patient’s pulse before administration; hold if <60 bpm
  - Monitor digoxin levels (therapeutic range: 0.5-2)
  - Watch potassium levels to prevent toxicity (hypokalemia increases risk)
- Treatment:
  - Bradycardia: Atropine (anticholinergic)
  - Digoxin toxicity: Digoxin immune fab (Digibind)
- Mnemonic: "Dig a hole slow and deep" - helps remember digoxin’s effect on heart contractions

Type: Sodium Channel Blockers
Medications: Procainamide, Lidocaine
- Both include "cain"
- Used for:
  - Ventricular dysrhythmias
  - Supraventricular tachycardia
- Side Effects:
  - Hypotension
  - Dysrhythmias
  - Lupus
  - Leukopenia
  - Thrombocytopenia
  - Black box warning: Risk of autoimmune response (positive ANA)
- Monitoring:
  - EKG, vital signs, CBC levels
  - Procainamide levels (therapeutic: 4-8)

Type: Beta Blockers
Medications: Propranolol, Metoprolol, Atenolol
- Used for:
  - Atrial fibrillation
  - Atrial flutter
  - Ventricular dysrhythmias
- Side Effects:
  - Hypotension
  - Bradycardia
  - Fatigue
  - Weakness
  - Erectile dysfunction
  - Bronchospasm (nonselective beta blockers like propranolol)
- Notes:
  - Nonselective beta blockers affect both beta-1 and beta-2 receptors, can cause bronchoconstriction, not suitable for asthma patients
  - Beta-1 blockers (Metoprolol, Atenolol) are safer for asthma patients
  - Mnemonic: "Please listen carefully" - Propranolol, Labetalol, Carvedilol affect beta-1 and beta-2