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

Adenosine Dosing for Supraventricular Tachycardia

For stable SVT, administer adenosine 6 mg as a rapid IV bolus followed immediately by a 20 mL saline flush; if no conversion occurs within 1-2 minutes, give 12 mg rapid IV bolus, which may be repeated once more for a maximum total dose of 30 mg. 1, 2

Initial Dosing Protocol

• Start with 6 mg IV push administered over 1-2 seconds through a proximal (large antecubital) vein, followed immediately by a 20 mL saline flush 1, 2
• The 6 mg initial dose successfully converts 70-80% of PSVT cases involving AVNRT or AVRT 2, 3
• If the rhythm does not convert within 1-2 minutes, administer 12 mg rapid IV bolus using the same technique 1, 2
• The 12 mg dose may be repeated once more if still no response after another 1-2 minutes 1, 2
• Maximum total cumulative dose is 30 mg 1, 3

Administration Technique

• Use the most proximal IV access available (closest to the heart) to ensure rapid delivery to central circulation 1, 2
• Administer as a rapid bolus over 1-2 seconds, not a slow push 1, 2
• Immediately follow with saline flush to propel the medication into central circulation before it is metabolized (half-life is less than 10 seconds) 2
• Maintain continuous ECG monitoring during administration to document conversion or help with diagnostic evaluation 1

Special Dosing Considerations

Reduce initial dose to 3 mg in the following situations: 1

• Patients taking dipyridamole or carbamazepine
• Cardiac transplant recipients (denervated hearts are hypersensitive)
• Administration via central venous access

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

• Theophylline
• Caffeine
• Theobromine

Clinical Context and Timing

• Adenosine should be attempted after vagal maneuvers fail (which terminate up to 25% of PSVT cases) 1
• For hemodynamically unstable patients, adenosine may be considered while preparations are made for synchronized cardioversion if the rhythm is regular and narrow-complex 1
• Have a defibrillator readily available when administering adenosine, particularly in patients where WPW syndrome is a consideration, as adenosine may precipitate atrial fibrillation with rapid ventricular response 1

Expected Outcomes and Success Rates

• Overall conversion rates range from 78% to 96% for AVNRT or AVRT 1
• The 6 mg dose converts approximately 70-80% of cases 2, 3
• An additional 15-20% convert with the 12 mg dose 3
• Recent prehospital data suggests that starting with 12 mg may reduce the need for repeat dosing and improve conversion rates, though this deviates from current guideline recommendations 4

Common Side Effects (Usually Transient)

All side effects last less than 60 seconds due to adenosine's extremely short half-life: 1, 2

• Flushing (most common)
• Dyspnea and chest discomfort
• Transient AV block
• Headache

Contraindications

Absolute contraindications: 1

• Severe asthma or active bronchospasm (adenosine can precipitate bronchospasm)

Use with extreme caution: 1

• Pre-excited atrial fibrillation or flutter (WPW syndrome) - may cause life-threatening rapid ventricular response
• Second- or third-degree AV block (unless pacemaker present)

Diagnostic Utility

• Adenosine may unmask atrial flutter or atrial tachycardia by transiently slowing AV conduction, even when it doesn't terminate the arrhythmia 1
• This diagnostic effect helps distinguish between different SVT mechanisms and guides subsequent therapy 1

If Adenosine Fails

• Consider longer-acting AV nodal blocking agents for stable patients: 1
  • Diltiazem 15-20 mg (0.25 mg/kg) IV over 2 minutes
  • Metoprolol 5 mg IV over 1-2 minutes, repeated every 5 minutes up to 15 mg total
• Proceed to synchronized cardioversion for hemodynamically unstable patients 1