Cat, yeast infection in ears

[superkat]

Hello everyone, I am new here and I am desperately looking for answers.
My cat had a dental treatment 6 days ago (several teeth were taken out) and he was prescribed antibiotic drops twice a day for 10 days (clindamycin hydrochloride 1cc every 12h) and transdermal gel with codeine 0.1cc twice a day spread inside inner part of the ear (switch ears). When I took the cat from the vet, his ears were more pink then usual, but I didn't pay much attention. After 4 days I noticed brown wax in both ears (we never had any ear infection before), my first thought was like maybe some dust set on the gel, I cleaned one ear, next day the brown wax came back. I googled and found the picture of cat with yeast ears infection - exactly same picture that I see on my cat's ears.
Did anyone had the same bad experience, can it be connected to medicines that I give him or could the cat be infected in the hospital?
I am going to take him to the hospital tonight but I would like to get some answers before I go there. Thank you.

[patchdog]

I have never had this happen with my cats. I am glad that you are taking him back to the vet to see what is going on. Please do let us know so we can be sure that it never happens to our babies.