One thing you might want to ask your vet about is the option to try dexamethasone vs prednisone.
EmilyB was on prednisone in her last years and it was pretty rough with the incontinence. (At this point, in case you need it, I will recommend a visit to a human health supply store to get the green rubber backed pads that can be washed (not dried in a dryer). These allowed Emily to pretty much sleep where she used to..................not going there......
)
Anyway, our new dobe has airborn allergies and went through three vets and a pile of drugs before we got positive results. She's now on allergy shots but crashes occasionally and needs a steroid, we tried prednisone, but when I told the vet it was getting pretty damp around here, she switched her to dex. Amazing difference.
Don't know if that is suitable in your situation, but just a thought I had tonight.