The following dose levels were investigated : once daily ( QD ) at two dose levels ( 400-and 800 mg ) , twice daily ( BID ) in five dose levels ( 600 - , 800 - , 1000 - , 1200 - and 1500 mg ) , and three times daily ( TID ) in three dose levels ( 800 - , 1000 - and 1200 mg ) .