Can we change the Generic product pH?

[kasis@drreddys.com (by way of John Dolman<info@the-dolman-consultancy.com>)]

Dear Forum, 
  
This is regarding parental preparation.
The Innovators pH and Generic product pH, can we change as per 21 CFR, a
drug product intended for parental use and same inactive ingredients and
in the same concentration as the reference listed drug. In this case we
need to prove any additional study other than stability. 
  
Is there any such guideline or
regulation in Europe? 
  
I will appreciate a reply for
this. 
  
Warm regards, 
Kasiseerapu