Study drug-related adverse events were significantly more frequent in the 600 mg group than in the 400 mg group ( 146 % [ 47 ] vs 118 [ 37 ] ) , difference -105 % , 95 % CI -182 to -28 ; p = 001 ) and significantly fewer patients with these events stopped treatment ( 400 mg = 6 [ 2 % ] , 600 mg = 18 [ 6 % ] , difference -396 % , 95 % CI -696 to -095 ; p = 001 ) .