The Reds, who had a five-game winning streak snapped Thursday, bounced back with an escape-filled pitching performance from Bronson Arroyo and a big inning that featured five extra base hits.
With Travis Wood on the mound and the Cubs leading 2-1, Ludwick tied the contest by hitting the first pitch of the fourth over the wall in left-center. After Jay Bruce was hit by a pitch, Frazier put the Reds in front for good a two-run blast.
Two outs later Arroyo helped his own cause with a double and then scored on a double by Zack Cozart. A triple by Drew Stubbs brought home the fifth and final run of the inning.
Arroyo (9-7) gave up nine hits but only three runs over 6 1/3 innings to get the win. All of the Cincinnati runs came off Wood (4-9), who left after five innings.
Cincinnati has produced a 21-7 record since July 18 to take command in the National League Central pennant race.
Ron Burgundy interviews Peyton Manning on SportsCenter
Toddler uninjured after being knocked over by Obama family dog