Reading pair Sean Morrison and Jordan Obita have both signed new contracts at the Madejski Stadium.
Ipswich defender Aaron Cresswell has signed a two-year extension to his contract.
The Clarets have netted 21 goals in their opening 10 npower Championship games, with striker Charlie Austin bagging 12 to comfortably lead the division's scoring charts.
But they have been breached 22 times and took only two points from games against Millwall, Sheffield Wednesday and Crystal Palace over the past week despite scoring on eight occasions.
"The statistics are there for everyone to see," Howe told Burnley's official website. "We score a lot of goals, but we are conceding too many so we have to address that problem quickly.
"That means hard work on the training ground and maybe for me to look into the loan market. There is only so long you can go on conceding the goals we are, so things have to change.
"So we will go away and think about it, and work with the players and we expect a response. Individually they are all good players, but defensively, individually and collectively, we haven't done well enough and I have to take responsibility for that as leader of the team."