What are the contraindications for adenosine?

Contraindications for Adenosine

Adenosine is absolutely contraindicated in patients with second- or third-degree AV block (unless they have a functioning artificial pacemaker), sinus node disease, bronchoconstrictive or bronchospastic lung disease (e.g., asthma), and known hypersensitivity to adenosine. 1

Absolute Contraindications

1. Second- or third-degree AV block (except in patients with a functioning artificial pacemaker) 1

   • Risk of prolonged bradycardia or asystole

2. Sinus node disease (such as sick sinus syndrome or symptomatic bradycardia) 1

   • Can worsen bradycardia in these patients

3. Bronchoconstrictive or bronchospastic lung disease 1, 2

   • Severe asthma is the most important contraindication
   • Can precipitate severe bronchospasm even in patients without known pulmonary disease 3

4. Known hypersensitivity to adenosine 1

Relative Contraindications and Cautions

1. Unstable angina or myocardial infarction 2

   • Adenosine may produce VF in patients with coronary artery disease 2

2. Pre-excited atrial fibrillation or flutter 2

   • Can accelerate ventricular response in patients with accessory pathways
   • May be particularly problematic for those with ventricular pre-excitation

3. Heart transplant recipients 2

   • Require reduced dosing (typically 3 mg initial dose)
   • Denervated hearts may have exaggerated response

4. Medication interactions 2

   • Dipyridamole: Potentiates adenosine effects, requires dose reduction
   • Carbamazepine: Higher rates of heart block may occur, requires dose reduction
   • Theophylline/caffeine: Antagonize adenosine effects, may require higher doses

5. Severe hypotension 2

   • May worsen existing hypotension

6. First-degree AV block or bundle branch block 2

   • Use with caution due to risk of progression to higher-degree block

Special Considerations

1. Pregnancy: Adenosine is considered safe and effective in pregnancy 2

2. Route of administration: When administered through central venous access, the initial dose should be reduced to 3 mg 2

3. Monitoring requirements:

   • ECG monitoring is essential during administration
   • A defibrillator should be available when adenosine is administered to any patient in whom WPW is a consideration 2

Clinical Pearls

• Transient side effects are common but typically brief due to adenosine's short half-life (20 seconds) 2
• Common side effects include flushing, dyspnea, and chest discomfort 2
• Dyspnea as a symptom is common and usually benign, but true bronchospasm requires immediate treatment 3
• Adenosine can help differentiate various types of supraventricular tachycardias but is not effective for terminating sinus tachycardia 4

Remember that while adenosine is generally safe when used appropriately, careful patient selection is essential to avoid potentially serious adverse events.