What is the typical rapid IV push dose of adenosine for acute SVT, and what is the expected effect?

• A. 12 mg IV push; may repeat to 24 mg
• B. 3 mg IV push; no repeats
• C. 6 mg IV push; may repeat with 12 mg
• D. 1 mg IV push; no AV block

Answer: (C)

Adenosine works by momentarily blocking conduction through the AV node, which is what often sustains a narrow-complex SVT. Because its half-life is extremely short, the drug must be given as a rapid IV push with a quick saline flush to reach the heart before it’s cleared.

The typical approach is an initial rapid dose of six milligrams. If there is no response within about a minute or two, a second dose of twelve milligrams is given. A third dose is rarely needed. The expected effect is an abrupt relaxation of the AV nodal conduction which interrupts the reentrant circuit responsible for the tachycardia, usually converting it back to normal sinus rhythm within seconds.

This dosing pattern—six milligrams first, then twelve milligrams if needed—best matches the standard rapid-acting regimen and the characteristic short-lived, AV-node–mediated effect of adenosine.