Vernakalant is a new antiarrhythmic drug that acts selectively in the atrium, targeting atrial specific channels: the Kv1.5 channel which carries IK(ur), and the Kir3.1/3.4 channel which carries IK(Ach). Vernakalant can also work to block Ito, late Ina, with minor blockade of IKr currents. Vernakalant is available in both intravenous and oral forms. In phase II and III trials, intravenous vernakalant has been shown to be effective in terminating acute onset atrial fibrillation whose duration is >3 hours and <7 days (∼50% efficiency vs. 10% for placebo). It does not appear to be effective for atrial fibrillation whose duration is >7 days, nor does it appear to be effective for atrial flutter. Studies with oral vernakalant have been designed to evaluate its efficacy and safety in the prevention of atrial fibrillation recurrence. Studies to date have shown that 51% of patients were able to maintain sinus rhythm after 90 days of using oral vernakalant 50 mg/kg twice daily compared with 37% of patients receiving placebo. Vernakalant appears to be a safe drug to use, with the most common side-effects being dysgeusia, sneezing, paresthesias, nausea, and hypotension. In the clinical trials, there were minimal drug-induced ventricular arrhythmias observed.