Adenosine Administration for Supraventricular Tachycardia (SVT)
The recommended dose of adenosine for SVT is an initial 6 mg rapid IV bolus, followed by up to two subsequent doses of 12 mg if the initial dose is ineffective, with each dose administered as a rapid bolus over 1-2 seconds followed by a saline flush. 1
Dosing Protocol
Initial Management
- First-line approach: Vagal maneuvers should be attempted first in hemodynamically stable patients (Class I, Level B-R) 1
- Adenosine administration:
- Initial dose: 6 mg rapid IV bolus over 1-2 seconds
- If no response within 1-2 minutes: 12 mg rapid IV bolus
- If still no response: May repeat 12 mg dose once more
- Maximum total: Three doses (6 mg, 12 mg, 12 mg)
- Safe administration of doses up to 24 mg has been reported in refractory cases 1
Administration Technique
- Administer as close to the heart as possible (proximal IV site)
- Follow immediately with a rapid saline flush
- Patient should be in a supine position during administration
- Have cardiac monitoring in place
Alternative Pharmacological Options
If adenosine is ineffective or contraindicated:
Calcium channel blockers:
- IV diltiazem: 0.25 mg/kg over 2 minutes, followed by infusion at 5-10 mg/hr
- IV verapamil: 5-10 mg over 2 minutes, may repeat with 10 mg after 30 minutes 1
Beta blockers:
- IV esmolol: 500 mcg/kg over 1 minute, followed by infusion at 50-300 mcg/kg/min
- IV metoprolol: 2.5-5.0 mg over 2 minutes, may repeat up to 3 doses 1
Special Considerations
Pregnancy
- Adenosine is considered safe during pregnancy (Class I, Level C-LD)
- The short half-life of adenosine (<10 seconds) makes it unlikely to reach fetal circulation 1
Refractory SVT
- Higher doses of adenosine (up to 24 mg) may be needed in patients with impaired venous return 2
- If pharmacological therapy fails, synchronized cardioversion is recommended (Class I, Level B-NR) 1
Hemodynamic Instability
- For hemodynamically unstable patients, proceed directly to synchronized cardioversion (Class I, Level B-NR) 1
Potential Adverse Effects
- Transient AV block
- Flushing, chest pain
- Dyspnea or bronchospasm (rare)
- Hypotension
- Potential for initiating atrial fibrillation 1, 3
Important Cautions
Contraindications:
- Second or third-degree AV block (unless patient has functioning pacemaker)
- Sick sinus syndrome or symptomatic bradycardia
- Known bronchoconstrictive or bronchospastic lung disease
- Known hypersensitivity to adenosine 3
Drug interactions:
- Methylxanthines (caffeine, theophylline) can reduce effectiveness
- Dipyridamole can potentiate adenosine effects 3
Recent Evidence
A 2025 study comparing initial adenosine dosing found that starting with 12 mg was associated with less re-dosing and greater rates of patient improvement compared to starting with 6 mg 4. However, current guidelines still recommend the 6 mg initial dose approach, as this has been established as safe and effective in most patients 1, 5.
Follow-up Management
After successful conversion: