A method of altering circadian rhythm in a mammal is provided. In certain embodiments, the method comprising: administering to the mammal a PDE5 inhibitor, e.g., sildenafil, vardenafil, tadalafil or zaprinast. The method may be employed to prevent a circadian rhythm disorders including, but not limited to transmeridian flight disorder (i.e., “jet-lag”), shiftwork-related disorder, seasonal affected disorder and insomnia by phase delay or phase advance.
USE OF PDE5 INHIBITORS FOR TREATING CIRCADIAN RHYTHM DISORDERS