The Manchester United man had been on standby but has been called into the full panel after a thigh strain put paid to Doyle's chances of participation
Doyle suffered the knock at Wolves training on Friday and a scan has confirmed the extent of the muscle injury.
Brady had been on the initial standby list for the two World Cup qualification encounters and has made the step into the full squad.
The Manchester United winger made his international debut against Oman last month in a friendly and impressed, scoring once and setting up two more and also featured for the Red Devils in their Capital One Cup tie against Newcastle United.
David Meyler, who also played against Oman, has also been drafted into the squad for the matches on October 12 and October 16.
Doyle scored Ireland's winner during their opening World Cup qualifier away at Kazakhstan last month and captained the side against Oman.