Florfenicol
Antibiotic
View Brand Names (2)Dose and dosage
Although florfenicol has been administered, some references cite adverse effects after administration. Until more safety data become available, it is suggested to avoid use of florfenicol in horses.
• 15 mg/kg IM in the neck q48h.
• Administer in drinking water at 400 mg/gallon (100 parts per million) for 5 consecutive days.
10–15 mg/kg body weight/day for 10 consecutive days
For susceptible systemic (bacterial or rickettsial) infections when myelotoxic potential (in humans or animals) of chloramphenicol is to be avoided: 20 mg/kg IM q8h for 3–5 days. (Greene et al. 2006)
a) For treatment of BRD: 20 mg/kg IM (in neck muscle only); repeat in 48 hours. Alternatively, a single 40 mg/kg SC dose (in neck) may be used.
Note: 20 mg/kg equates to 3 mL of the injection per 100 lb. of body weight. Do not exceed 10 mL per injection site.
b) For treatment of BRD: 40 mg/kg (6 mL/100 lb B.W.) administered once by subcutaneous injection. Do not administer more than 15 mL at each site. The injection should be given only in the neck. Injection sites other than the neck have not been evaluated. (Label Information;
c) Using the combination product containing florfenicol/flunixin : 40 mg/kg florfenicol/2.2 mg/kg flunixin (6 mL/100 lb. B.W.) SC
once. Do not administer more than 10 mL at each site. The injectionshould be given only in the neck. Injection sites other than the neck have not been evaluated.
For susceptible systemic infections (bacterial or rickettsial) infections when myelotoxic potential (in humans or animals) of chloramphenicol is
to be avoided: 22 mg/kg IM, PO q12h for 3–5 days (Note: Oral dosage form not available, but solution given orally to experimental cats was well absorbed) (Greene et al. 2006)
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Florfenicol has been shown to be effective for treatment of BRD in cattle associated with Mannheimia haemolytica, Pasteurella multocida, and Histophilus somni. It also
is used for treatment of bovine interdigital phlegmon (foot rot, acute interdigital necrobacillosis, and infectious pododermatitis) associated with Fusobacterium necrophorum and Bacteroides melaninogenicus and for treatment of infectious bovine keratoconjunctivitis caused by Moraxella bovis.
In pigs, florfenicol is used for treatment of swine respiratory disease (SRD) caused by Actinobacillus pleuropneumoniae, Pasteurella multocida, Salmonella choleraesuis,
and Streptococcus suis.
In cats, effective concentrations can be achieved with twice-daily administration. In dogs, the half-life is short, and frequent administration is necessary to produce effective concentrations. Florfenicol also has been administered to fish.
Long-term use in animals may cause bone marrow suppression.
Long-term use should be avoided in dogs and cats
Administration to horses has caused diarrhea, colitis, and elevations in bilirubin. Administration to horses is not recommended.
Do not administer more than 10 mL in a single site.
Mode of Action:
Florfenicol has a broad spectrum of antibacterial activity that includes all organisms sensitive to chloramphenicol, gram-negative bacilli, gram-positive cocci, and other atypical bacteria such as mycoplasma. Florfenicol is highly lipophilic, which provides high enough concentrations to treat intracellular pathogens and cross some anatomic barriers (penetration across the blood–brain barrier in cattle is 46%). It acts by binding to the 50S ribosome, thereby inhibiting bacterial protein synthesis.
Pharmacokinetics:
The half-life of florfenicol is 2–3 hours in cattle after IV administration, but it is prolonged (18 hours) after IM injection and 27 or 62 hours (depending on the study) after 40 mg/kg SQ. The peak concentration in cattle after 40 mg/kg SQ is 5.5 mcg/mL. In dogs, the half-life is shorter, with values of 1.1 and 1.2 after IV and oral administration, respectively. The half-lives in cats are approximately 4 hours and 7.8 hours after IV and oral administration, respectively. The protein binding is small.
florfenicol could antagonize the bactericidal activity of the penicillins or aminoglycosides. Other antibiotics that bind to the 50S ribosomal subunit of susceptible bacteria (erythromycin, clindamycin, lincomycin, tylosin, etc.) may potentially antagonize the activity of chloramphenicol or vice versa, but the clinical significance of this potential interaction has not been determined.
dose-dependent bone marrow depression
In toxicology studies where feeder calves were injected with up to 10X th erecommended dosage, the adverse effects noted above were seen, plus increased serum enzymes. These effects were generally transient in nature. Long-term (43 day) standard dosage studies showed a transient decrease
Safety or effects when used in breeding cattle or swine, during pregnancy, or during lactation are unknown and the manufacturer states that the drug is not for use in cattle of breeding age or in swine intended for breeding.
Cattle withdrawal time (meat): 28 days if administered IM; 38 days if administered SQ.
(40 mg/kg SQ) is 44 days.
Sheep: Apply at least 42-day slaughter withdrawal time.
Do not use in calves to be processed for veal.
Pig withdrawal time: 16 days after last treatment when administered in water; 13 days after last treatment when administered with feed.