Adeyeye, in a Facebook post on Thursday night, said the notice for the meeting got to him late.
Buhari met with the APC Senators Wednesday evening after a mass exodus of senators from the ruling party on Tuesday.
Adeyeye who is a professor said he was at the University of Ibadan College of Medicine on Wednesday, to deliver a public lecture when he got the invitation for the meeting.
He said the notice got to him only “around 7pm”, while the university event was “scheduled for over five months”.
Adeyeye said, “it was logistically impossible for me to head to Abuja” at the time he learnt of the meeting.
“My colleagues of the APC caucus were fully aware of my engagement at Ibadan. I also sent an apology to the President pertaining to my absence.
“For the avoidance of any doubts, I remain a firm member of the APC. I have never partaken of any formal or informal meeting with the r-APC,” he wrote.