Florfenicol: veterinary dose and monograph

At a glance

Drug class

Antibiotic

Also known as

Nuflor, Resflor, Norfenicol

Species with doses

Dogs, Cats, Cattle, Goats, Sheep, Pigs and Buffalo

General dose range

20–40 mg/kg IM 48 h interval (cattle) / 24 h (other) — check the species tables for the indication

Routes

IM, SC, PO

Last reviewed

1 October 2026

Indications

• Bovine respiratory disease (BRD) — Mannheimia, Pasteurella, Histophilus, Mycoplasma
• Bovine infectious pododermatitis (foot rot, Fusobacterium necrophorum)
• Swine respiratory disease (Actinobacillus pleuropneumoniae, Pasteurella, Streptococcus suis)
• Caprine / ovine BRD (extra-label)
• Canine / feline susceptible infections (extra-label, off-FDA-label)

Florfenicol dose by species

Doses are per administration unless stated. mg/kg doses scale with body weight; per-animal, per-quarter and infusion-rate doses are shown as the reference writes them.

Dogs

• Susceptible infection (extra-label): Papich 5e: 20 mg/kg q6h IM or PO. Plumb’s p.527 (Greene 2006): 20 mg/kg IM q8h for 3–5 days where chloramphenicol’s myelotoxic risk is to be avoided. IM injection may be painful.

Cats

• Susceptible infection (extra-label, uncommon): Papich 5e: 22 mg/kg q8h IM or PO. Plumb’s p.527 (Greene 2006): 22 mg/kg IM or PO q12h for 3–5 days (the injectable solution given orally was well absorbed).

Cattle

• BRD — IM neck only: Plumb’s p.527 (Nuflor label): 20 mg/kg IM in the neck muscle only; repeat in 48 h. 3 mL per 100 lb; no more than 10 mL per site. Slaughter withdrawal 28 days after IM use (38 days after SC). Not for female dairy cattle 20 months or older, veal calves, or IV use.
• BRD — single SC dose (Nuflor Gold): Plumb’s p.527 (Nuflor Gold label): 40 mg/kg (6 mL/100 lb) SC once, in the neck only; no more than 15 mL per site. Slaughter withdrawal 44 days. Beef and non-lactating dairy cattle only.
• Foot rot: Nuflor label: 40 mg/kg SC once in the neck (or 20 mg/kg IM, repeat at 48 h). Plumb’s p.527: slaughter withdrawal 38 days after SC use of the standard 300 mg/mL product (28 days IM).

Horses

• Not recommended: Papich 5e: some references cite adverse effects after florfenicol in horses; until more safety data are available, avoid its use in this species.

Goats

• Respiratory disease in kids (extra-label): Plumb’s p.527 (de la Concha 2002): kids 20 mg/kg once daily for 2 days (route not stated; assume IM). Extra-label — obtain a FARAD withdrawal.

Sheep

• Respiratory disease (extra-label): Papich 5e: sheep 20–30 mg/kg IM or 40 mg/kg SC once daily for 3 days. Extra-label — obtain a FARAD withdrawal.

Pigs

• Swine respiratory disease: Papich 5e: 15 mg/kg IM in the neck q48h. Plumb’s 10e p.529 (label dosage; FDA-approved): 15 mg/kg IM, second dose 48 hours later. WITHDRAWAL — Plumb’s 10e p.530 (NuFlor-S, 300 mg/mL, US label): slaughter withdrawal 11 days after IM use at label doses; do not use in nursing piglets or swine of reproductive age intended for breeding. Confirm the local product label.
• Swine respiratory disease — drinking water: Papich 5e and Plumb’s p.527 (NuFlor Concentrate Solution label): 100 ppm in drinking water for 5 consecutive days. Slaughter withdrawal 16 days.

Buffalo

• Respiratory disease / haemorrhagic septicaemia adjunct: Dosed as cattle (Indian labels include buffalo): Papich 5e and Plumb’s p.527 — 20 mg/kg IM in the neck, repeated after 48 h, or 40 mg/kg SC once in the neck; ≤10 mL per site IM. Follow the local label withdrawal (US cattle label: 28 days after IM, 38 days after SC).

Contraindications

Not for use in animals intended for breeding (reproductive effects undetermined). NOT for lactating dairy cattle. Hypersensitivity to florfenicol or chloramphenicol-class drugs. Adult ruminants on PO route — destroys rumen flora. Strict withdrawal: 38 d slaughter (cattle, IM) / 44 d (Nuflor Gold SC) / 11 d (swine).

Species-specific warnings

Cattle: NOT for lactating dairy. 38 d slaughter (IM) / 44 d (Gold SC) withdrawal. Neck IM only — max 10 mL per site.

Pigs: 15 mg/kg IM × 2 with 48 h interval. 11 d slaughter withdrawal.

Cats: Avoid extra-label use in cats — fluorinated chloramphenicol class; insufficient feline data and historical chloramphenicol concerns.

Adverse effects

• Cattle: anorexia, decreased water consumption, diarrhoea (transient)
• Injection-site reactions, particularly with large IM volumes — limit 10 mL per site
• Rare hepatic / renal enzyme elevations

Drug interactions

• Other myelosuppressives (cyclophosphamide, azathioprine): potential additive bone marrow effects
• Rifampin: may decrease florfenicol concentrations (hepatic induction)
• Chloramphenicol / lincomycin / erythromycin: similar binding site — antagonism possible

Pregnancy and lactation

NOT for breeding cattle, pregnant cows, or lactating dairy — reproductive effects undetermined and milk discard is unacceptable. Extra-label in pregnant small animals: caution; insufficient data.

Monitoring

• Withdrawal strictly: 38 d slaughter (Nuflor IM) / 44 d (Nuflor Gold SC) / 11 d (swine)
• Clinical response within 24–48 h — repeat IM dose at 48 h or treat with alternative if no improvement
• Injection-site swelling — rotate sides of neck

Clinical pearls

• BRD — Nuflor 20 mg/kg IM (neck) at hours 0 and 48 is the workhorse pattern in Indian dairy / feedlot
• Single-shot convenience: Nuflor Gold 40 mg/kg SC is one injection per case — useful for chute work
• Foot rot: 40 mg/kg SC single (Nuflor Gold) often clears acute interdigital necrobacillosis within 3 days
• Never IM in dairy cows on milk — withdrawal is not established for lactation; switch to oxytetracycline if milking
• Cap IM volume at 10 mL per site — large volumes cause sterile abscess and reduce absorption

Mechanism of action

Synthetic fluorinated analogue of chloramphenicol — binds 50S ribosomal subunit at the peptidyl transferase site, inhibiting bacterial protein synthesis. Time-dependent bactericidal activity against BRD pathogens at clinical concentrations. The fluorine substitution prevents the irreversible aplastic anaemia seen with chloramphenicol in humans / cats. Wide tissue distribution including lung (4–5× plasma) and CSF (>30% plasma).

Formulations and products

• Nuflor 300 mg/mL injection
• Nuflor Gold 300 mg/mL (long-acting SC, cattle)
• Nuflor (MSD Animal Health) — 300 mg/mL, IM injection (cattle, swine)
• Nuflor Gold (MSD Animal Health) — 300 mg/mL long-acting, Single-shot SC injection (cattle, neck only)

Storage

15–25 °C, protect from freezing. Multidose vial: 28 d after broaching. Discard discoloured vials.

Before you use this dose

Reference doses for veterinary professionals. Confirm the dose against the product label, the patient’s condition, current guidance and local regulations before use; the attending veterinarian remains responsible for every clinical decision.

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• Danofloxacin
• Doxycycline
• Enrofloxacin
• Erythromycin
• Fusidic Acid
• Gamithromycin
• Gentamicin
• Levofloxacin

Frequently asked questions