Wolves' Matt Doherty and Aberdeen's Jonny Hayes remain in contention for Republic of Ireland debuts in the games against Switzerland and Slovakia.
Brentford's Alan Judge is also in line for a debut but uncapped Peterborough man Chris Forrester drops out after his inclusion in the initial 40-man squad.
Anthony Stokes, Darron Gibson, Paul Green, Simon Cox, Greg Cunningham and keeper Keiren Westwood also drop out.
The Republic meet the Swiss on 25 March before facing Slovakia four days later.
Both friendlies will take place at the Aviva Stadium in Dublin.
Defender Doherty, winger Hayes and midfielder Forrester had all been handed their first Republic call-ups in the initial extended squad.
Stoke City defender Marc Wilson is a notable absentee as he currently has a knee injury which is expected to keep him out until at least the end of April.
Republic of Ireland squad:
Darren Randolph (West Ham United), David Forde (Millwall), Rob Elliot (Newcastle United)
Cyrus Christie (Derby County), Seamus Coleman (Everton), Richard Keogh (Derby County), John O'Shea (Sunderland), Alex Pearce (Bristol City), Shane Duffy (Blackburn Rovers), Ciaran Clark (Aston Villa), Paul McShane (Reading), Stephen Ward (Burnley), Matt Doherty (Wolverhampton Wanderers)
Robbie Brady (Norwich City), James McCarthy (Everton), Jeff Hendrick (Derby County), Harry Arter (Bournemouth), Eunan O'Kane (Bournemouth), Glenn Whelan (Stoke City), Stephen Gleeson (Birmingham City), David Meyler (Hull City), Stephen Quinn (Reading), Aiden McGeady (Sheffield Wednesday), James McClean (West Bromwich Albion), Alan Judge (Brentford), Jonny Hayes (Aberdeen), Anthony Pilkington (Cardiff City), Jonathan Walters (Stoke City), Wes Hoolahan (Norwich City)
Robbie Keane (LA Galaxy), Shane Long (Southampton), Daryl Murphy (Ipswich Town), Kevin Doyle (Colorado Rapids)