Adenosine is widely found in nature and plays an important role in biochemical processes, such as energy transfer—as adenosine triphosphate (ATP) and adenosine diphosphate (ADP)—as well as in signal transduction as cyclic adenosine monophosphate (cAMP). It is also a neuromodulator, believed to play a role in promoting sleep and suppressing arousal. Adenosine also plays a role in regulation of blood flow to various organs through vasodilation.
Adenosine is an endogenous nucleoside analog that alters electrical conduction at the atrioventricular (AV) node and has a negative chronotropic effect on the sinoatrial node. Adenosine acts on cardiac A1 receptors to reduce cyclic adenosine monophosphate activity, which decreases inward calcium conductance and diminishes pacemaker current, resulting in bradycardia, AV nodal blockade, and sinus pauses. It has a very short half-life time (less than 10 seconds) and is rapidly taken up by the vascular endothelium and erythrocytes. The effect on heart rate is seen within 10 to 20 seconds after administration, with the duration of asystole reaching a plateau between 40 to 60 seconds at 1 mg/kg. There is a relative hypotension period of 1 minute after asystole.