Would you consider adding or switching to pirfenidone for a patient with progressing UIP (based on imaging and PFTs) who is currently on nintedanib?  

Yes, I would consider it. There's some recent literature addressing this, which indicates switching may be associated with disease amelioration. Why might it work? Not super clear, perhaps biologic differences or maybe driven by better compliance. Smarter people than me could probably speak to the r...

Maybe. In my mind, it makes sense as both the drugs are probably working on different mechanisms but I am not aware that we have any study (especially well-conducted RCT) for that purpose. Also, it might create a coverage of insurance as well. 

No!