What is the recommended initial dose of adenosine (adenosine) for paroxysmal supraventricular tachycardia (PSVT)?

Recommended Dose of Adenosine for PSVT

The recommended initial dose of adenosine for paroxysmal supraventricular tachycardia (PSVT) is 6 mg administered as a rapid IV bolus over 1-2 seconds through a large vein (e.g., antecubital), followed by an immediate 20 mL saline flush. 1, 2

Standard Dosing Protocol

• First dose: 6 mg IV rapid bolus
• Second dose: If no response within 1-2 minutes, administer 12 mg IV rapid bolus
• Third dose: If still no response, a second 12 mg dose may be given (maximum total dose of 30 mg) 2

Special Dosing Considerations

• Reduced initial dose (3 mg) is recommended for:

  • Patients taking dipyridamole or carbamazepine
  • Heart transplant recipients
  • When administered via central venous access 1, 2

• Increased initial dose may be required for:

  • Patients with significant blood levels of theophylline, caffeine, or theobromine 1, 2

Administration Technique

1. Administer adenosine over 1-2 seconds
2. Follow immediately with a rapid 20 mL saline flush
3. Maintain continuous ECG monitoring during administration
4. Have a defibrillator available, especially if WPW syndrome is suspected 1

Efficacy and Safety

Adenosine is highly effective for PSVT involving the AV node, with a 90-95% effectiveness rate for AVNRT and AVRT 2. Its extremely short half-life (0.6-10 seconds) makes adverse effects transient, providing advantages over calcium channel blockers due to its rapid onset and minimal negative inotropic effects 3, 4.

Contraindications and Precautions

• Absolute contraindications:

  • Severe bronchospastic lung disease
  • Significant heart block 2

• Use with caution in patients with:

  • Asthma
  • Pre-excitation syndromes (WPW)
  • Significant heart block 2

Common Side Effects

• Flushing
• Chest discomfort
• Shortness of breath
• Transient AV block
• Potential to initiate atrial fibrillation 2, 4

Clinical Pearls

• Adenosine is safe to use in pregnancy due to its extremely short half-life 2
• The drug works by blocking the anterograde AV nodal limb of a re-entrant circuit 3
• Adenosine has diagnostic utility in differentiating between AVNRT/AVRT and other arrhythmias 2
• Vagal maneuvers should be attempted first when appropriate before administering adenosine 1, 2

Common Pitfalls to Avoid

1. Inadequate flush: Failure to administer an immediate saline flush after adenosine can reduce efficacy
2. Incorrect administration site: Using small peripheral veins can lead to drug degradation before reaching the heart
3. Failure to recognize contraindications: Administering to patients with severe asthma or significant heart block
4. Misdiagnosis: Adenosine has minimal effect on automatic focal AT and will not terminate atrial fibrillation or flutter (though it may transiently slow ventricular rate) 1, 2

Adenosine's rapid onset and short duration of action make it the preferred initial pharmacologic treatment for stable PSVT when vagal maneuvers fail, with a significantly faster time to conversion compared to verapamil (34.2 seconds vs. 414.4 seconds) 5.