The trio were in a provisional 34-man squad named by Martin O'Neill last month for the two legs starting at Copenhagen's Parken Stadium before the return in Dublin three days later.
Keogh came off early in Derby County's defeat by Reading in the Championship on Saturday, with Everton's McCarthy sidelined since making his only club appearance this season on Oct. 25.
However. O'Neill is hoping Burnley midfielder Jeff Hendrick will be fit for the first leg after he suffered a glute injury against Southampton in their Premier League game on Saturday.
"Jeff came off after about 60 odd minutes, he was having a bit of a problem and he's still a little bit sore at the moment," O'Neill told a news conference.
"He's said he's improving so that's good news. If the game was tomorrow morning he might struggle but he's pretty hopeful and the medical team are hopeful."
O'Neill cut David McGoldrick, Jonny Hayes, Daryl Horgan and Alan Browne from a squad now numbering 27 including David Meyler who will be available for the second leg after suspension.
There was no call up for Burnley striker Jonathan Walters, who was left out of the original squad after missing the final two games of the campaign and still has a knee problem.
Fullback Seamus Coleman is a long-term absentee after breaking his leg on international duty in March.
(Writing by Ken Ferris; Editing by Steve Keating in Toronto.)
