Florfenicol : A Broad-Spectrum Antibiotic for Livestock and Pets

Florfenicol, sold under the brand name, is a powerful broad-spectrum antibiotic used in the treatment of various bacterial infections in livestock, including cattle, swine, and fish. Although primarily approved for use in cattle, florfenicol may also be beneficial for treating infections in other species such as dogs and cats. In this article, we will explore the uses, pharmacology, precautions, and dosage guidelines for florfenicol.

Uses and Indications:

Florfenicol is primarily indicated for the treatment of bovine respiratory disease (BRD) associated with bacteria such as Pasteurella haemolytica, Pasteurella multocida, and Haemophilus somnus in cattle. Its broad-spectrum activity against a wide range of microorganisms, including Mycoplasma, suggests potential use in treating other infections in cattle and possibly other species. However, more specific data regarding its efficacy in these cases is limited.

Pharmacology and Actions:

Similar to chloramphenicol, florfenicol acts by binding to the 50S ribosome of bacteria, inhibiting bacterial protein synthesis. This mechanism of action provides florfenicol with its broad-spectrum activity against many bacterial strains.

Pharmacokinetics:

In cattle, approximately 79% of a dose of florfenicol is bioavailable after intramuscular (IM) injection. The drug is well-distributed throughout the body, including the cerebrospinal fluid (CSF), with a volume of distribution of about 0.7 L/kg. Only 13% of florfenicol is bound to serum proteins. The mean serum half-life in cattle is approximately 18 hours, but individual variation exists.

In dogs, florfenicol is poorly absorbed after subcutaneous injection, with an elimination half-life of less than 5 hours. Oral administration in dogs results in good bioavailability (95%), but the drug is rapidly eliminated (elimination half-life of 1.25 hours).

Cats exhibit high absorption of a 100 mg/mL solution of florfenicol when given either IM or orally, with an elimination half-life of less than 5 hours. In cats, the time above an MIC (minimum inhibitory concentration) of 2 mg/mL was 12 hours (IM) and 18 hours (oral), and the time above an MIC of 8 mg/mL was 10 hours (IM) and 6 hours (oral).

Contraindications, Precautions, and Warnings:

While no contraindications are listed in the package insert, caution should be exercised when administering florfenicol. Intravenous administration should be avoided, and the drug should not be given to veal calves or cattle of breeding age, as per the manufacturer's instructions. Additionally, caution should be taken to prevent injection site reactions that may result in trim loss, especially when administering the drug at sites other than the neck.

Adverse Effects:

Transient adverse reactions in cattle may include anorexia, decreased water consumption, and diarrhea. Injection site reactions can occur, potentially leading to trim loss. When used in other species, gastrointestinal effects, including severe diarrhea, are possible.

Reproductive and Nursing Safety:

The safety and effects of florfenicol on breeding cattle, swine, pregnancy, and lactation are unknown. The manufacturer advises against using the drug in cattle of breeding age or in swine intended for breeding.

Dosage Guidelines:

Cattle:

- For the treatment of BRD: Administer 20 mg/kg IM (in the neck muscle) and repeat after 48 hours. Alternatively, a single 40 mg/kg subcutaneous (SC) dose may be used. Do not exceed 10 mL per injection site.

Dogs:

- For susceptible systemic bacterial or rickettsial infections: Administer 20 mg/kg IM every 8 hours for 3-5 days.

Cats:

- For susceptible systemic bacterial or rickettsial infections: Administer 22 mg/kg IM or orally every 12 hours for 3-5 days. Note: Oral dosage form is not available commercially.

Sheep and Goats:

- For respiratory disease complex in kids: Administer 20 mg/kg per day (route not specified) for 2 days.

Florfenicol is a broad-spectrum antibiotic commonly used in the treatment of bovine respiratory disease in cattle. While primarily approved for use in cattle, it may also be beneficial in treating infections in other species such as dogs and cats. Understanding its uses, pharmacology, precautions, and dosage guidelines is crucial for veterinarians and livestock owners. Always consult a veterinarian for appropriate dosage and administration instructions based on the specific needs of the animal being treated.