Percent reduction in partial-onset seizure frequency/week over PBO was -0.9 % ( p = 0.885 ) for BRV 5 mg/day , 4.1 % ( p = 0.492 ) for BRV 20 mg/day , and 12.8 % ( p = 0.025 ) for BRV 50 mg/day ( mITT population ) .