Regadenoson. Molecular model of the drug regadenoson (C15.H18.N8.O5?H2.O). This long-acting beta A2A adenosine receptor agonist is sold under the brand name Lexiscan. It is used in pharmacologic stress testing. It produces hyperaemia quickly and maintains it for a duration that is useful for radionuclide myocardial perfusion imaging. Atoms are represented as spheres and are colour-coded: carbon (grey), hydrogen (white), nitrogen (blue) and oxygen (red).