Young cats or dogs may have discoloration of their teeth if given a large enough of a dosage. Anaphylaxis or cardiovascular collapse may occur in rare instances. Symptoms may include ataxia, facial swelling, trouble breathing, drooling, and a general restlesness.
In dogs, oxytetracycline HCL may cause urolith (crystals) to form in the urinary tract. Cats are even more likely to suffer from urolith formation, along with possible fever, depression, and hair loss.