My dog was exposed to kennel cough. I took him to the vet and he has been on meds. for 7 days. still not eating or playing the way he did. I am concerned.
I would give it another week and if he is still coughing go back to the vet. he may need a stronger antibiotic. the reason I say this is that I had a pup that contracted a nasty form of kennel cough that did not respond to the first four antibiotics we gave her. she didn't want to eat much or play. the vet. put her on the second strongest antibiotic (erythomyacin-excuse spelling) on the list in fact I had to get it at the pharmacy because vets' don't keep it on hand. she started to get a little better but it still took two rounds of the antibiotic to get her well. I know there was some lung damage because she will cough a little in the winter months but is fine in the summer. one round of meds. may not be enough.
We have a labrador and she has had kennel cough twice, about a year apart each time.
She was sick for about 2 weeks from start to finish so give it until that sort of time frame before you start to worry. As long as he is on the medication he will come good again.
While he is sick don't let him exhaust himself so keep him quiet and well rested. When he is starting to feel better he will run around again on his own. then you know he's on the mend.