Adenosine is a short acting endogenous molecule that is a purine nucleoside. The half-life is 6 seconds. Adenosine receptor activation results in multiple different actions depending on the location. Adenosine plays an important role in energy transfer (adenosine triphosphate or ATP) and in cellular signaling (cyclic AMP).
The cardiovascular uses of adenosine relate to its ability to block the AV Node. Giving a 6 mg IV bolus followed by a saline flush can be helpful during a narrow complex tachycardia. This can terminate AVNRT (AV nodal reentry tachycardia) and sometimes atrial tachycardia as well. Adenosine will slow, not terminate, atrial fibrillation and atrial flutter allowing an accurate diagnosis to be made (which is frequently difficult when the heart rates are fast).
Due to the short half-life, the saline flush is very important or else the drug may be completely metabolized before it reaches the heart. The dose should be decreased to 3 mg IV bolus if a central line is being used. Frequently, 12 mg IV bolus is needed if the IV line is in the hand. Transplanted hearts are very sensitive to adenosine and dose reduction and close monitoring is recommended. Brief asystole frequently occurs after adenosine bolus, however this is very rarely sustained. Adenosine is infrequently used to induce cardiac stress to detect occlusive coronary artery disease now that regadenoson is available. Caffeine and other methylxanthines can block the effects of adenosine and should be avoided 24 hours prior to use for stress testing. Also, persantine is similar in mechanism of action, thus adenosine should be avoided in patients taking this medication.
By Steven Lome