Addisons Dog Panting/ Coughing

Question
I adopted my approx. 3 yr old (9.6 lb)poodle mix about 3 months ago. After a few days we noticed her picking at her ear. After 3 rounds of antibiotics, no improvement. then she started vomiting, stopped eating or drinking, became lethargic and dehydrated. Took her to the Dr to have a culture on the ear and address the sickness. To cut it short, he did the culture and also did blood work which showed high potassium,low sodium etc. (signs of Addison's) and the culture showed 2 bacteria which he described as "bad boys." He did the ACTH test which came back positive for Addison's and put her on 2 antibiotics for the ear. Well, she has had a Percorten shot and had her first blood work yesterday and her potassium and everything was "perfect" according to her Dr. She is also on prednisolone every day. After ending up at the ER for being dehydrated again her Dr. upped her dose of prednisolone to .5 ml and could give a little extra for known upcoming stressful situations. She started panting alot, even just laying on the couch, so I backed off the pred, and her Dr. agreed that I was correct. But, today she seems like she is having difficulty breathing, it is kind of erratic. Slow and labored at times and fast at others. I have also noticed that she will kind of open her mouth on every breath or pant when I take her out to potty and she kind of coughs after she drinks. Do you think it is a side effect from the prednisolone or could it be something worse, like a heart issue?

Answer
Well I answered this once and my answer was lost in cyberspace.
While dogs with Addison's can certainly have a myriad of problems a 3 yr old dog seems a bit young for these problems.

However since he did test her I am sure the diagnosis was correct.
Prednisolone itself causes water retention so it might be interfering with her breathing but a .5 mg pill isn't enough to do that(usually).
My concern would be to have him listen to her heart again and access whether or not the pred is doing this.

Open mouth breathing is a real sign of distress so I would be very concerned about this.
I would call her vet first thing Tuesday and have him look her over again and be sure he does address the breathing and her heart.
Let me know what he says.