Cat won't accept intramuscular antibiotics anymore

Hi everyone,

I've got a cat that got an ear infection from fighting . The infection got quite big with puss and the vet prescribed intramuscular antibiotics.

I have managed to give him the injection for 3 days but now It is very painful for him/the cat will scream and moves his leg very violently so he might damage his leg. The cat has only one day left of his injection. The three previous days he accepted the medicine well . I followed the procedure correctly ie sterilized the injection site, injected in the proper muscle group and depth, aspirated etc .

What do I do ? I will go to the vet tomorrow to ask for advice and I'm hoping that he gives me the same antibiotic orally as I don't think the cat will accept it anymore in the current route . The cat is in good health ie he can eat solid food and moves around but he still has puss discharge from his ear. From the time when I need to do the injection to me going to the vet there will be about 12 hours. Will there be any problem with antibiotic resistance/the medicine not working if I need to continue it tomorrow? Do you think my cat will recover properly or there be any complications ?

Thanks!