What is the initial dose of adenosine (adenosine) for supraventricular tachycardia (SVT)?

Adenosine Dosing for SVT

The initial dose of adenosine for supraventricular tachycardia is 6 mg administered as a rapid IV push over 1-2 seconds through a proximal vein, followed immediately by a 20 mL saline flush. 1, 2, 3

Initial Dosing Protocol

• Start with 6 mg IV push administered rapidly over 1-2 seconds, not as a slow infusion 1, 2, 3
• Follow immediately with a 20 mL normal saline flush to propel the medication into central circulation before it undergoes rapid metabolism 1, 2, 4
• Use the most proximal IV access available (antecubital or higher) to ensure rapid delivery to the heart 2, 4

Escalation Strategy if Initial Dose Fails

• If no conversion occurs within 1-2 minutes, administer 12 mg IV push using the same rapid technique 1, 2, 3
• The 12 mg dose may be repeated once more if still no response after another 1-2 minutes 1, 2, 3
• Maximum cumulative dose is 30 mg total (6 mg + 12 mg + 12 mg) 2

Expected Success Rates

• The initial 6 mg dose successfully converts 70-80% of PSVT cases involving AVNRT or AVRT 2, 3
• Overall conversion rates with the full dosing protocol range from 78-96% 2, 4
• Approximately 95% of AVNRT cases terminate with adenosine 4

Special Dosing Modifications

Reduce initial dose to 3 mg in these specific situations: 1, 2, 4

• Patients taking dipyridamole or carbamazepine
• Cardiac transplant recipients (due to denervation hypersensitivity)
• Administration via central venous access

Higher doses may be required for patients with significant blood levels of: 1, 2, 4

• Theophylline
• Caffeine
• Theobromine (these are adenosine receptor antagonists)

Critical Safety Considerations

• Have a defibrillator immediately available before administering adenosine, particularly when Wolff-Parkinson-White syndrome is a consideration, as adenosine may precipitate atrial fibrillation with rapid ventricular rates 1, 4
• Maintain continuous ECG monitoring during administration to document conversion or aid in diagnostic evaluation 2, 4
• Contraindicated in severe asthma or active bronchospasm due to risk of precipitating bronchospasm 1, 2, 4
• Use with extreme caution in pre-excited atrial fibrillation/flutter, second- or third-degree AV block 2, 4

Administration Technique Matters

• The medication must be given as a rapid bolus over 1-2 seconds, not a slow push, to ensure adequate concentration reaches the AV node before metabolism 2, 3
• Adenosine has an extremely short half-life of less than 10 seconds, making rapid administration and immediate saline flush essential 3, 5

Common Pitfalls to Avoid

• Slow administration: This is the most common error—adenosine will be metabolized before reaching the heart if pushed slowly 2, 3
• Distal IV access: Using hand or wrist IVs reduces success rates due to metabolism during transit 2, 4
• Inadequate or delayed saline flush: The flush must be immediate and forceful to propel adenosine centrally 1, 2
• Starting with 12 mg: While recent prehospital data suggests 12 mg initial dosing may improve conversion rates and reduce hospital admissions 6, current guideline recommendations remain 6 mg initially to minimize dose-dependent side effects, as 70-80% of patients convert with this lower dose 1, 2, 3

Expected Transient Side Effects

• Flushing, chest discomfort, dyspnea, and transient AV block are common but last less than 60 seconds due to the ultra-short half-life 1, 3, 4
• Rare complications include transient complete heart block and initiation of atrial fibrillation (1-15% of cases) 3

If Adenosine Fails

• Consider longer-acting AV nodal blocking agents (diltiazem 15-20 mg IV or metoprolol 5 mg IV) for stable patients 1, 4
• Proceed to synchronized cardioversion for hemodynamically unstable patients 3, 4
• Adenosine failure may unmask atrial flutter or atrial tachycardia by transiently slowing AV conduction, providing diagnostic value even without terminating the arrhythmia 2, 4

Pregnancy Consideration

• Adenosine is safe and effective during pregnancy 4