Adenosine for Supraventricular Tachycardia
Adenosine is the first-line pharmacologic treatment for acute SVT after vagal maneuvers, with a Class I recommendation and 90-95% success rate in terminating AV node-dependent tachycardias. 1
Initial Management Algorithm
Start with vagal maneuvers first (Valsalva, carotid massage, ice-cold towel to face) in hemodynamically stable patients with regular SVT before proceeding to adenosine. 1
If vagal maneuvers fail or are not feasible, proceed immediately to adenosine administration. 1
Adenosine Dosing Protocol
Administer via large proximal vein as rapid IV push followed immediately by 20 mL saline flush: 2
- Initial dose: 6 mg IV push 1, 2
- If no conversion within 1-2 minutes: 12 mg IV push 2
- If still no conversion: repeat 12 mg IV push 2
Dose Modifications
Reduce initial dose to 3 mg in these specific situations: 2
- Patients taking dipyridamole or carbamazepine
- Transplanted hearts
- Central venous access administration
Increase doses may be required for: 2
- Patients with significant theophylline, caffeine, or theobromine blood levels
Success Rates and Effectiveness
Adenosine terminates approximately 95% of AVNRT cases and 90-95% of orthodromic AVRT. 1 In real-world emergency department experience, 73% respond to the 6 mg dose, 15% to the second 12 mg dose, and 11% to a third dose. 3
Recent evidence suggests starting with 12 mg may be superior: A 2025 study found that initial 12 mg dosing was associated with 65% increased odds of prehospital improvement and 28% reduction in hospital admission compared to 6 mg initial dosing, with no difference in complications. 4 However, current ACC/AHA/HRS guidelines still recommend the 6 mg initial dose. 1
Essential Safety Requirements
A defibrillator must be immediately available when administering adenosine, particularly in patients where Wolff-Parkinson-White syndrome is a consideration, as adenosine may precipitate atrial fibrillation with rapid ventricular conduction that can degenerate to ventricular fibrillation. 1, 2
Absolute Contraindications
Do not administer adenosine in: 5
- Second- or third-degree AV block (unless functioning pacemaker present)
- Sinus node disease or symptomatic bradycardia (unless functioning pacemaker present)
- Asthma or bronchospastic lung disease (risk of severe bronchospasm) 2, 5
- Known hypersensitivity to adenosine
Hemodynamically Unstable Patients
Proceed directly to synchronized cardioversion in hemodynamically unstable patients (hypotension, altered mental status, shock, chest pain, acute heart failure). 1 However, adenosine may be considered first if the tachycardia is regular with narrow QRS complex. 1
Diagnostic Value
Continuous ECG recording during adenosine administration is essential as it serves dual therapeutic and diagnostic purposes. 2 If adenosine does not terminate the rhythm, it will unmask underlying atrial activity (atrial flutter, atrial tachycardia), helping distinguish between drug failure and successful termination with immediate reinitiation. 1, 2
Common Side Effects
Most patients (>80%) experience transient side effects: 3
- Chest tightness/discomfort (83%)
- Flushing (39-40%)
- Dyspnea
- Sense of impending doom (7%)
These effects resolve within seconds to one minute due to adenosine's 0.6-10 second half-life. 6
Post-Conversion Management
Monitor closely for recurrence after successful conversion. 2 If SVT recurs, options include:
- Repeat adenosine administration 2
- Transition to longer-acting AV nodal blocking agent (diltiazem, verapamil, or beta-blocker) 2
If adenosine reveals atrial flutter or atrial tachycardia rather than terminating the rhythm, treat with a longer-acting AV nodal blocking agent. 2
Special Population: Pregnancy
Adenosine is safe and effective during pregnancy with Class I recommendation. 1, 2 Use standard dosing (6 mg initial, then 12 mg if needed). 1
Critical Pitfall to Avoid
Never give adenosine to patients with pre-excited atrial fibrillation (irregular wide-complex tachycardia in WPW). This can cause life-threatening ventricular rates and degeneration to ventricular fibrillation. 1 In pre-excited AF, use procainamide or ibutilide instead, or proceed directly to cardioversion if unstable. 1