Side Effects of Penicillin on Cats

Penicillin is an antibiotic used in both humans and animals to treat bacterial infections. In cats, penicillin can be used alone or combined with other drugs. It is effective against skin infections, dental infections, gastrointestinal infections and bladder infections. Penicillin can cause side effects in cats that range from mild to severe, even when used as directed.

  1. Diarrhea

    • Although penicillin is used to treat gastrointestinal infections, it can also cause gastrointestinal problems. A cat's gastrointestinal tract has bacteria to help it break down and digest food. Penicillin can kill off this bacteria, upsetting the balance in the intestinal tract and cause diarrhea. Diarrhea is common in pets being treated with penicillin and other antibiotics, according to Petplace.com. If your cat develops diarrhea during or after a course of antibiotics, notify your veterinarian.

    Vomiting

    • Vomiting is a less-common side effect of penicillin than diarrhea, but it still occurs occasionally. Penicillin, especially if taken orally, can upset the stomach and cause nausea and vomiting. If your cat is nauseous, he may lose his appetite as well. Vomiting may also be an extension of the gastrointestinal changes that cause diarrhea.

    Other Side Effects

    • Other side effects penicillin can cause include drooling, skin rashes, yeast or fungal infections and anemia, which can cause symptoms such as bruising easily and bleeding.

    Allergic Reaction

    • A lot of cats are allergic to penicillin, according to Vetinfo.com. Signs of an allergic reaction include hives, swelling of the lips, face or tongue, rash and fainting. If your cat exhibits any of these symptoms, you should discontinue the penicillin and call your veterinarian immediately.