Adenosine Dosing for Supraventricular Tachycardia (SVT)
The recommended initial dose of adenosine for supraventricular tachycardia (SVT) is 6 mg administered as a rapid IV bolus over 1-2 seconds, followed by an immediate saline flush. 1, 2
Administration Protocol
- Initial dose: 6 mg IV rapid bolus (injected as proximal to the heart as possible)
- Administration technique: Deliver over 1-2 seconds followed by rapid saline flush
- If no response within 1-2 minutes: Administer 12 mg IV rapid bolus
- If still no response: May repeat 12 mg dose once more (maximum total dose: 30 mg)
- Continuous ECG monitoring should be maintained during administration
Special Dosing Considerations
Reduced Initial Dosing (3 mg)
- Patients taking dipyridamole or carbamazepine
- Heart transplant recipients
- When administered via central venous access 2, 1, 3
- A study demonstrated that 77% of SVT episodes were terminated with just 3 mg when administered centrally 3
Increased Initial Dosing
- Patients with significant blood levels of theophylline, caffeine, or theobromine may require higher doses 1
Efficacy and Outcomes
Adenosine is highly effective for SVT involving the AV node, with:
- 90-95% effectiveness rate for AVNRT and AVRT 1
- Recent research suggests a 12 mg initial dose may be associated with:
- Less need for redosing (25% vs 48% with 6 mg)
- Greater rates of patient improvement
- Lower rates of hospital admission 4
- However, current guidelines still recommend the 6 mg initial dose
Contraindications and Precautions
- Absolute contraindications: Severe bronchospastic lung disease, significant heart block
- Use with caution:
- Asthma or bronchospastic lung disease
- Pre-excitation syndromes (risk of accelerated conduction through accessory pathway)
Common Adverse Effects
- Flushing, chest discomfort, shortness of breath
- Transient AV block
- Potential to initiate atrial fibrillation (especially concerning in patients with WPW)
- Bronchospasm (rare)
Clinical Pearls
- Adenosine has an extremely short half-life (0.6-10 seconds), making adverse effects transient
- It offers advantages over calcium channel blockers and beta-blockers due to rapid onset and minimal negative inotropic effects
- Adenosine has diagnostic utility in differentiating between AVNRT/AVRT and other arrhythmias
- Complications requiring interventions (cardioversion, pacing, CPR) are rare with proper administration
Remember that adenosine should be considered first-line therapy for acute termination of stable SVT, with vagal maneuvers attempted first when appropriate.