What medication should be administered if carotid massage fails in treating supraventricular tachycardia (SVT)?

Adenosine is the appropriate medication to administer if carotid massage fails in treating supraventricular tachycardia (SVT) because it works specifically to interrupt certain reentrant pathways within the heart. This action effectively transiently blocks conduction through the atrioventricular (AV) node, which can terminate the SVT.

When delivered intravenously, adenosine has a very short half-life and can quickly restore normal sinus rhythm in patients experiencing SVT. It is particularly indicated for cases of paroxysmal SVT and is a first-line treatment in emergency settings for this arrhythmia.

In contrast, other medications such as amiodarone, while useful for treating various types of supraventricular and ventricular tachycardias, are generally not the first choice in acute SVT management due to their longer onset times and broader spectrum of action. Atropine is primarily used for symptomatic bradycardia rather than SVT, and magnesium sulfate is mostly utilized in the treatment of torsades de pointes or for cases of hypomagnesemia rather than as a primary treatment for SVT. Thus, adenosine's rapid action in specifically addressing the pathology of SVT makes it the correct choice in