Having gone out of the Europa League on Thursday, the Foxes were given an early tonic by the Gunners as Youri Tielemens was allowed to run unchecked down the right before firing a low shot into the far corner with just six minutes played.
Arsenal refused to be adversely affected, though, and took control of the game with impressive attacking intent and far greater fluency than the hosts.
David Luiz brought them level, finding space in the box to steer a header in from Willian's free-kick.
It was second time lucky for the Gunners, who had earlier had a penalty awarded on the pitch but then downgraded to a free-kick after VAR decided the offending tackle on Pepe had taken place just outside the area.
Ivory Coast forward Pepe got in on the act himself, tapping into a largely unguarded net after Willian's pass had deflected his way.
Afterwards, Lacazette remarked: "The reaction was good after the goal we conceded.
"Everyone kept their focus, we stayed with the game plan and when everyone is like this it makes it easier to win games.
"I think it is important that everyone plays well. Recently we have been talking about the youngsters who have been playing really, really well.
"But as senior players, we have to be ready and to be good so that we don't have to rely only on the youngsters."