Maximum Dose of Adenosine for PSVT
The maximum cumulative dose of adenosine for acute termination of paroxysmal supraventricular tachycardia in adults is 30 mg total (6 mg + 12 mg + 12 mg), though safe use of 18 mg bolus doses has been reported in clinical practice. 1
Standard Dosing Protocol
The ACC/AHA/HRS guidelines establish the following dosing sequence for adenosine administration: 1
Initial dose: 6 mg rapid IV bolus administered over 1-2 seconds through a large proximal vein, followed immediately by a 20 mL saline flush 1, 2
Second dose: If no conversion within 1-2 minutes, administer 12 mg rapid IV bolus with saline flush 1, 2
Third dose: If still no response, one additional 12 mg dose may be given 1, 2
Maximum cumulative dose: This yields a total of 30 mg (6 + 12 + 12 mg) 1
Evidence for Higher Doses
The ACC/AHA/HRS guidelines explicitly note that "the safe use of 18-mg bolus doses has been reported," indicating that single boluses exceeding the standard 12 mg maximum have been used safely in clinical practice. 1 This is particularly relevant for patients with impaired venous return or those taking methylxanthines (theophylline, caffeine) who may require larger doses. 2, 3
Dose Modifications for Special Circumstances
Reduce the initial dose to 3 mg in the following situations: 2
- Patients taking dipyridamole or carbamazepine (these potentiate adenosine's effects) 2
- Patients with transplanted hearts (denervated hearts are hypersensitive to adenosine) 2
- Administration via central venous access (77% of patients respond to 3 mg centrally vs. 37% peripherally) 4
Increase doses may be required for: 2
- Patients with significant blood levels of theophylline, caffeine, or theobromine (competitive antagonists at adenosine receptors) 2
- Patients with impaired venous return to the right heart (e.g., pulmonary hypertension with right heart failure) 3
Efficacy Data by Cumulative Dose
The dose-response relationship demonstrates: 5
- 3 mg cumulative: 35.2% conversion rate 5
- 6 mg cumulative (3 + 3 or single 6 mg): 57-62% conversion rate 5
- 9 mg cumulative: 80.2% conversion rate 5
- 12 mg cumulative: 91.4% conversion rate 5
Overall success rates for the standard protocol (6 mg followed by up to two 12 mg doses) range from 90-95% for AVNRT and 78-96% for AVRT. 2, 6
Critical Safety Considerations
Absolute contraindications to adenosine include: 6
- Asthma or bronchospastic lung disease (risk of severe bronchospasm) 1, 2, 6
- Second- or third-degree AV block or sick sinus syndrome without a pacemaker 1, 6
High-risk situations requiring extreme caution: 6
- Wolff-Parkinson-White syndrome with atrial fibrillation (adenosine can precipitate rapid ventricular rates via the accessory pathway) 2, 6
A defibrillator must be immediately available when administering adenosine to any patient in whom WPW syndrome is a consideration. 2
Administration Technique
The extremely short half-life of adenosine (<10 seconds) mandates proper administration technique to ensure the drug reaches the heart before degradation: 6, 7
- Use the most proximal IV site available (antecubital preferred over hand) 1
- Administer as a rapid push over 1-2 seconds 1
- Follow immediately with a 20 mL saline flush 2
- Elevate the extremity after injection to facilitate venous return 2
Common Pitfalls
Over 10% of adult patients will not respond to the standard maximum doses of adenosine, particularly those with impaired venous return or methylxanthine use. 3 In refractory cases after reaching the 30 mg cumulative maximum, transition to alternative AV nodal blocking agents (diltiazem 15-20 mg IV over 2 minutes achieves 64-98% conversion, or verapamil 5-10 mg IV) rather than exceeding adenosine dosing limits. 2
The average time to termination after effective adenosine administration is 30 seconds; if no effect is seen within 1-2 minutes, the dose was insufficient and the next higher dose should be given. 1, 5