Vernakalant (RSD1235, 3-pyrrolidinol) is a NCE being developed to treat acute episodes of atrial fi brillation (AF). The drug selectively blocks sodium and potassium ion channels in the heart that are known to be active during such episodes. It was originated by Cardiome Pharma (then Nortran Pharmaceuticals) in the 1980s, when one of the company’s main R&D programmes was for the discovery of small molecules that act on ion channels for the treatment of arrhythmia.