Cardiovascular

Antiarrhythmics (Class I, II, III, IV)

Cardiovascular

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Examples

lidocaine (Class I)metoprolol (Class II)amiodarone (Class III)verapamil (Class IV)

Prefix / Suffix: No consistent suffix

Physiology

Cardiac rhythm depends on proper electrical conduction through the heart. Abnormal ion movement (sodium, potassium, calcium) can disrupt this, leading to arrhythmias.

Mechanism of Action

Class I (Na⁺ blockers): slow conduction. Class II (beta blockers): ↓ heart rate and conduction. Class III (K⁺ blockers): prolong repolarization. Class IV (Ca²⁺ blockers): slow AV node conduction.

Indications

  • Atrial fibrillation
  • Ventricular arrhythmias
  • Supraventricular tachycardia

Side Effects / Adverse Effects

  • Bradycardia (due to slowed conduction)
  • Hypotension (due to reduced cardiac activity)
  • Proarrhythmia (can worsen or cause new arrhythmias)
  • Amiodarone: pulmonary toxicity (drug accumulates in lungs)

Contraindications

  • Severe bradycardia
  • Heart block
  • Cardiogenic shock

Nursing Considerations

  • Monitor ECG continuously (detects arrhythmias or conduction changes early)
  • Check HR and BP before giving (risk of bradycardia and hypotension)
  • Watch for new or worsening arrhythmias (proarrhythmic effect is a key exam point)
  • For amiodarone: monitor lung function, liver enzymes, thyroid levels (drug accumulates in multiple organs)
  • Avoid combining multiple antiarrhythmics unless prescribed (increases risk of severe dysrhythmias)

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Disclaimer: PharmPal Nurse is for education only and is not medical advice. Do not use it to diagnose, treat, prescribe, or make patient-care decisions; always verify with current drug references, your instructor, facility policy, and a licensed provider. In emergencies, call local emergency services.