What Causes Sleepiness While On Oxetol?

im male 45yrs 3yrs back iwas in the hospital for suspected seizure which they did not confirm later i met dr arjundos in chennai who asked me why i was prescribed oxetol when they could not confirm seizure but anyway ive been on this medicine for about 3.5yrs now if i sit idle i just fall asleep is this because of the tablet i would verymuch appreciate an early reply