Emergency Medicine : Know your drugs

ADENOSINE

A 67-year-old man who has suffered a previous stroke is admitted with collapse. His drug history includes the use of dipyridamole. On examination he has a regular pulse of 150 bpm. You elect to try intravenous adenosine to slow his heart down. Which of the following best fits the characteristics of adenosine?

1.	Its half-life is decreased by dipyridamole
2.	It may be used after beta-blockade
3.	The half-life of adenosine is around 15 seconds
4.	It is effective in cardioverting ventricular tachycardia
5.	It can be used in cases of sick-sinus syndrome

Answer: 3. may be used after beta-blockade

Adenosine is an ultra short-acting antiarrhythmic drug with a half-life of 8–10 seconds, although this is prolonged when administered in patients taking dipyridamole. Unlike verapamil it may be used following beta-blockade.

Indications for adenosine are rapid cardioversion of supraventricular tachycardia including those associated with accessory pathways, eg Wolff–Parkinson–White syndrome, and for the diagnosis of rapid arrhythmias. It is contraindicated in patients with second- or third-degree heart block and sick-sinus syndrome. Adenosine does not convert ventricular tachycardia. Side-effects include transient facial flushing and a choking sensation, where patients often clutch their chest (worth warning patients of this in advance if possible). An escalating dose schedule of 3, 6 and 12 mg is usually employed.0.1 mg/kg rapid IV push(1to3 second) follow immediately with >5 ml NS flush