Two days is still early days for treatment but you should start seeing some improvement in the next day or so, I would say to give it the weekend and if there is no improvement in Jinx’s condition you should return to your Veterinarian on Monday for another examination. Improvement in an animal's condition, especially with antibiotics, can be delayed in most cases so unless your Veterinarian said specifically ‘you’ll see improvement over the next 24 hours’ or something similar you should give it three or four days at least. Regards Dr Callum Turner DVM
Rapid breathing (tachypnea) is a respiratory disorder characterised by abnormal breathing that is rapid and shallow. It is caused by a reduced level of oxygen, mechanical disorders (where the lungs aren’t able to expand as they should, usually due to a build-up of fluid in or around the lungs), and physiological disorders in which the cat’s respiratory centre in the brain is over stimulated.