What is the first dose of adenosine in the tachycardia protocol?

• A. 6 mg
• B. 12 mg
• C. 1 mg
• D. 3 mg

Answer: (A)

Adenosine works by briefly blocking conduction through the AV node, which can stop AV-node–dependent tachycardias and reveal the underlying rhythm. Because it acts so quickly and is cleared from the body in a matter of seconds, it must be given as a rapid IV bolus to reach the heart before it wears off.

The standard starting dose is six milligrams, delivered as a rapid IV push with an immediate saline flush to push the drug toward the heart. If there’s no response, the protocol calls for a second dose of twelve milligrams, and sometimes another twelve milligrams after that if needed. Lower doses, like one or three milligrams, are unlikely to produce the needed AV nodal block, and twelve milligrams is reserved for a subsequent attempt rather than the initial dose.