Hello Hugo's There,
I am new to the forum and just read your thread. I have a rabbit that has very similiar symptoms to Dexter. She started coughing last January and due to teeth root problems was on depocillin and vet hoped it would work on the cough as well. She was admitted in March with breathing difficulties, was put on oxygen and had heart scan and x-ray's nothing showed up, vet said it was possibly a lung abscess, and we began nebulising.
The coughing and sneezing continued but she was coping well and then at the end of April started to rattle it didn't cause her any problem and she was running around and eating as normal. She carried on with the sneezing, coughing and rattle until the end of July when we tried Septrin which cleared it until December when the sneezing and coughing and rattle returned, she had congested lungs and Septrin was prescribed again.
Unfortunately she is also a dental bunny and had a dental at the end of January but had laboured breathing and buldging eyes after. She was put on Frusol and another heart scan was booked which showed up clear. The coughing and sneezing has continued, and last Saturday the rattle returned, she was put on Baytril and is still on Frusol, the rattle stopped Sunday afternoon, but no doubt it will return.
Tomorrow once again she has to have a dental and just hoping she pulls through. I wish your Dexter well and will look with interest to any updates.