If the initial adenosine 6 mg dose does not terminate AVNRT/AVRT, what is the next recommended dose?

• A. 12 mg IV bolus
• B. 24 mg IV bolus
• C. 6 mg IV infusion
• D. 3 mg IV bolus

Answer: (A)

Adenosine terminates AVNRT and AVRT by causing a very brief block of AV nodal conduction, which interrupts the reentrant circuit that relies on AV nodal pathways. The drug acts with a rapid onset and an extremely short half-life, so it’s given as a rapid intravenous bolus to achieve an immediate spike in AV block.

If the first 6 mg dose does not stop the tachycardia, the next step is to give a rapid bolus of 12 mg. This higher dose increases the likelihood of achieving a complete AV nodal blockade quickly, thereby terminating the reentrant circuit. If needed, a third bolus of 12 mg can be considered, with careful monitoring and attention to the total dose (typically up to about 30 mg overall).