What is the maximum dose for the second adenosine administration in the stable narrow complex tachycardia protocol?

• A. 4 mg
• B. 8 mg
• C. 10 mg
• D. 12 mg

Answer: (D)

When treating stable narrow complex tachycardia, adenosine is given as a rapid IV push to transiently block AV nodal conduction and often terminate the reentrant SVT. The protocol uses a two-dose approach: start with a 6 mg dose, and if there’s not an adequate response, give a second dose. The second dose is limited to 12 mg, making that the maximum for the second administration. This higher second dose is chosen to increase the chance of success while staying within safety limits, given adenosine’s very short half-life. Lower amounts like 4 mg, 8 mg, or 10 mg don’t align with the protocol’s second-dose maximum.