The present invention relates to the use of 3,7-diazabicyclo[3,3,1]nonane compounds, preferably of 9,9-alkylene-3,7-diazabicyclo[3,3,1]nonane compounds, and most preferably to the use of tedisamil, and the physiologically acceptable acid addition salts and / or solvates thereof, in the form of a liquid pharmaceutical preparation for the treatment and / or inhibition of anti-arrhythmic events in human patients, preferably in conversion of recent onset of atrial fibrillation or flutter to normal sinus rhythm in humans. Furthermore, the invention concerns related methods of treatment and pharmaceutical products.