By Rania Gollakner, BS, DVM, MPH

What is chloramphenicol?

Chloramphenicol (brand names Chloromycetin® and 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 in cats, rabbits, hedgehogs, rodents, ferrets, birds, and reptiles. Many drugs are commonly prescribed for off-label use in veterinary medicine. In these instances, follow your veterinarian’s directions and cautions very carefully.

How is chloramphenicol given?

Chloramphenicol comes in tablet form, capsules, as a liquid suspension, and in an injectable form (chloramphenicol sodium succinate). Tablets, capsules, and liquid suspensions should be given by mouth with food. Measure liquid forms carefully. Injectable forms will be administered by your veterinarian.

The tablets are extremely bitter and even hiding the tablets in food may not cover the bitter taste. If you are having trouble giving the tablets to your pet, other forms of the medication should be tried.

This medication will take effect quickly, in about one to two hours, but outwardly effects may take a few days to be recognized.

What if I miss giving my pet the medication?

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 giving your pet a dose, give the next dose as soon as you remember, and then wait the recommended amount of time between doses. If it is close to the next scheduled dose when you remember, maintain the regular schedule. Never give your pet two doses at once or give extra doses.

Are there any potential side effects?

Vomiting, diarrhea, and anorexia (decreased appetite) are quite common side effects. With prolonged treatment or higher doses, bone marrow function can be affected and may cause lethargy, bruising, or paleness. Dogs may experience weakness and lack of muscle coordination resulting in difficulty walking. Cats are much more sensitive and more susceptible to experiencing side effects of this drug and should be monitored closely.

This short-acting medication should stop working within 24 hours, although effects can be longer in pets with liver or kidney disease.

Are there any risk factors for this medication?

Chloramphenicol should be used with extreme caution or avoided in animals with blood disorders, such as anemia. Use cautiously in animals with liver or kidney disease. Chloramphenicol should not be administered to dogs used for breeding, or in pregnant or nursing females. Its use should be avoided in very young or very old animals. Pets should not be vaccinated while taking this medication.

NOTE: Exposure in humans can have severe consequences that are irreversible, so care must be taken to avoid accidental exposure. Gloves should be worn when handling the medication. DO NOT crush pills, as inhaling the drug is just as dangerous as touching or consuming it – crushing the pills creates powders that can become airborne. If your pet vomits after giving this drug, wear gloves while cleaning up.

Are there any drug interactions I should be aware of?

Caution must be taken when chloramphenicol is used in conjunction with many anesthetics, barbiturates (e.g., phenobarbital), salicylates (e.g., aspirin), and some other antibiotics (e.g., penicillins, cephalosporins). Be sure to tell your veterinarian about any medications (including vitamins, supplements, or herbal therapies) that your pet is taking.

Is there any monitoring that needs to be done with this medication?

Monitoring of the levels of this drug in the blood may be recommended by your veterinarian. This ensures that the correct amount of medication is being administered. If long-term use is expected, blood tests, including complete blood counts, may be necessary before treatment begins and every two days during the treatment. Monitor for efficacy and for side effects.

How do I store chloramphenicol?

Store chloramphenicol in a tightly sealed container, protected from light, and at room temperature (below 25°C or 77°F).

What should I do in case of an emergency?

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.

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