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Is FISS a concern for cats receiving multiple daily injections?

Updated on September 23, 2025

Pet's info: Cat | Mixed Breed | Male | neutered

My cat is taking subcutaneous amoxicillin+clavulanic acid injections daily (Sinulox) for 7 days. Should I worry he might develop feline injection site sarcoma (FISS)? I know it's more common in certain types of vaccines, but I read that it might also be associated with other injections, especially because it's not just one application, but several in a row. Thanks

1 Answer

Most Helpful Answer

Linda G,  MS, DVM

Answered By Linda G, MS, DVM

Veterinarian

Published on January 17, 2021

Hello. It is true that FISS can be associated with other injections besides vaccinations. We have seen sarcomas develop in areas where long-acting antibiotic & steroids have been injected, where suture material might remain, & from microchips. So, there might be a genetic predisposition for a sarcoma to form in these situations.
If this is the only way to get the antibiotic into your cat, then varying the injection sites & doing this for the shortest period possible is recommended. But it is never a foregone conclusion that this will lead to sarcoma formation in Camis. Most cats do very, very well & never develop any problems. Thanks for contacting Petco Pet Education Center, formerly Petcoach.
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