Which characteristic is true of adenosine when used to treat PSVT?

• A. It has a long half-life
• B. Prolongs depolarization and is given as a rapid IV push to treat PSVT
• C. Is a calcium channel blocker
• D. Is used to treat hypertension

Answer: (B)

Adenosine works best for PSVT because it is ultra-short–acting and must reach the heart quickly to interrupt the reentrant circuit at the AV node. It does this by activating A1 receptors in the AV node, causing hyperpolarization through potassium channel opening. That brief hyperpolarization transiently blocks AV nodal conduction, effectively producing a short pause that allows the rhythm to reset to normal. Because the drug is cleared extremely fast by adenosine deaminase, its effects last only a few seconds, which is why it is given as a rapid IV push (often followed by saline) to deliver the dose quickly before it’s metabolized. It is not a calcium channel blocker, it does not prolong depolarization, and it isn’t used to treat hypertension. Common, transient side effects reflect the sudden AV nodal block and rapid onset/offset.