In an unstable patient with PSVT non-responsive to vagal maneuvers, which medication is commonly administered first?

In the context of treating unstable patients experiencing paroxysmal supraventricular tachycardia (PSVT) that do not respond to vagal maneuvers, the first medication commonly administered is adenosine IV. Adenosine acts quickly to interrupt the re-entry pathways in the heart, which is crucial during an acute PSVT episode.

Adenosine is favored in emergency situations because it has a very short half-life, allowing for rapid assessment of its effectiveness. The administration of this medication can lead to a temporary heart block, which often terminates the tachycardia. It is particularly beneficial in cases where the PSVT is causing significant symptoms or hemodynamic instability, necessitating immediate intervention.

While other options such as digoxin, metoprolol, and calcium channel blockers may be used in the management of PSVT, they are not typically the first-line treatment in acute crises. Their onset of action is slower compared to adenosine, making them less suitable in emergency settings. Thus, administering adenosine IV is critical in promptly addressing unstable PSVT cases.