What is the initial dose of adenosine for SVT?

• A. 3 mg slow IV push
• B. Adenosine is not used for SVT
• C. 6 mg rapid IV push
• D. 12 mg rapid IV push

Answer: (C)

Adenosine works by briefly blocking AV nodal conduction, which can interrupt reentrant circuits that cause narrow-complex SVT. Because its half-life is extremely short, it must be given as a rapid IV bolus so it reaches the heart before it’s cleared. The standard starting dose in adults is 6 mg given rapidly (over 1–2 seconds), followed immediately by a rapid saline flush (about 20 mL). If there is no conversion within 1–2 minutes, a second dose of 12 mg rapid IV push is given, and a third 12 mg dose may be used if needed. The other options don’t fit because 3 mg given slowly won’t reliably achieve AV nodal block, 12 mg is reserved for a second dose, and adenosine is indeed a first-line treatment for stable narrow-complex SVT.