A pharmaceutical composition comprising lidocaine N-oxide (LNO), or a pharmaceutically acceptable salt thereof, for use in a method of treatment, said method being a prophylactic treatment to prevent, or decrease the likelihood of, sudden cardiac death associated with ventricular fibrillation (VF) in a subject, whereby the composition is provided to the subject's bloodstream via the oral mucous membrane or via pulmonary absorption in the lungs or by IV administration.