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Chloramphenicol (brand names Chloromycetin®, Viceton®) is a broad-spectrum antibiotic used to treat many different gastrointestinal, pulmonary, and urinary bacterial infections, including those caused by anaerobic bacteria (bacteria that do not require oxygen for survival or growth) and Rickettsia (the bacteria that causes Rocky Mountain spotted fever).
It is approved for use in dogs and horses but is used off label (extra label) in cats, rabbits, hedgehogs, rodents, ferrets, birds, and reptiles. Many drugs are commonly prescribed for off-label use in veterinary medicine. “Off label” means the drug is being used in a way that has not been reviewed or approved by the U.S. Food and Drug Administration (FDA) or Health Canada. In these instances, follow your veterinarian’s directions and cautions carefully, as they may be significantly different from those on the label. .
Chloramphenicol is considered a hazardous drug, and exposure in humans can have serious and irreversible consequences, so it is essential avoid accidental exposure.
This medication will take effect quickly, in about one to two hours, but effects may not be noticeable for a few days.
It is very important to give the medication at the prescribed intervals. Missing a dose can cause the drug not to work properly. If you miss a dose, give it as soon as you remember, and then wait the recommended time for the next dose, as prescribed by your veterinarian However, if it is almost time for the next dose, skip the missed dose and resume the regular dosing schedule. Do not give the pet two doses at once.
Chloramphenicol may cause the following side effects:
Monitor cats closely, as they are much more sensitive and more susceptible to experiencing side effects of this drug.
Other side effects may occur. If you notice anything unusual, contact your veterinarian immediately. This short-acting medication should stop working within 24 hours, although effects can be longer in pets with liver or kidney disease.
DO NOT USE chloramphenicol in:
USE WITH EXTREME CAUTION in:
USE WITH CAUTION in:
Do not vaccinate your pet while it is taking this medication.
Several medications should be used with caution when given with chloramphenicol, including:
Be sure to tell your veterinarian about any medications (including vitamins, supplements or herbal therapies) that your pet is taking before starting any treatment.
If you suspect an overdose or an adverse reaction to the medication, call your veterinary office immediately. If they are not available, follow their directions in contacting an emergency facility. Be prepared to provide information about the product and your pet's weight and symptoms. If human exposure to the medication occurs, wash the area thoroughly. If the drug is inhaled, contact your doctor.
© Copyright 2025 LifeLearn Inc. Used and/or modified with permission under license. This content written by LifeLearn Animal Health (LifeLearn Inc.) is licensed to this practice for the personal use of our clients. Any copying, printing or further distribution is prohibited without the express written consent of LifeLearn. This content does not contain all available information for any referenced medications and has not been reviewed by the FDA Center for Veterinary Medicine, or Health Canada Veterinary Drugs Directorate. This content may help answer commonly asked questions, but is not a substitute for medical advice, or a proper consultation and/or clinical examination of your pet by a veterinarian. Please contact your veterinarian if you have any questions or concerns about your pet’s health. Last updated on Jun 11, 2025.
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