Florfenicol API: Veterinary Antibiotic for Respiratory Infections

Name: Florfenicol
SKU: 73231-34-2
Availability: InStock

Quick Facts

CAS Number	73231-34-2
Molecular Formula	C₁₂H₁₄Cl₂FNO₄S
Molecular Weight	358.21
Pharmacopoeia	CVP, IN HOUSE
Packaging	25 KG/DRUM

GMP Certified

Product Overview

Florfenicol was developed by Schering-Plough Corporation (now part of Merck Animal Health) and launched in the 1990s as Nuflor. Its development was driven by an urgent regulatory problem: chloramphenicol, the most important amphenicol antibiotic against respiratory pathogens, had been banned from food-animal use in the United States (1985) and Europe (1994) due to a rare but fatal idiosyncratic aplastic anemia risk in humans. Thiamphenicol, the immediate chloramphenicol analog, had a better safety profile but was susceptible to the same bacterial acetylation-based resistance mechanism. Florfenicol solved both problems in a single molecule.

The critical structural innovation was replacing the C-3 hydroxyl group of thiamphenicol with a fluorine atom. This single-atom substitution achieved two goals simultaneously: (1) The fluorine atom is not a substrate for bacterial chloramphenicol acetyltransferase (CAT), making florfenicol active against chloramphenicol- and thiamphenicol-resistant strains. (2) The molecule lacks the p-nitro group of chloramphenicol — the moiety responsible for aplastic anemia — resulting in a fundamentally different toxicological profile that allowed regulatory approval for food animals. This elegant structural design made florfenicol the first amphenicol-class antibiotic approved for use in food-producing animals, setting the stage for its widespread adoption across aquaculture, cattle, swine, and poultry sectors.

Florfenicol is now the dominant veterinary antibiotic in global aquaculture, where its broad-spectrum activity against aquatic pathogens (Aeromonas salmonicida, Vibrio anguillarum, Streptococcus iniae, Edwardsiella ictaluri) and stability in medicated feed make it the first-line treatment for bacterial disease outbreaks in finfish and shrimp. In terrestrial livestock, its excellent lung tissue penetration — achieving lung-to-plasma ratios well above 1 — makes it a first-line injectable for poultry respiratory disease (BRD). The aquaculture sector accounts for the largest volume share of global florfenicol consumption, driven by the rapid expansion of intensive aquaculture production in China, Vietnam, India, Indonesia, and Ecuador.

As of mid-2026, the global florfenicol API market continues to grow at approximately 5-7% annually, led by aquaculture demand in Asia-Pacific and Latin America. China is the dominant producer, with API synthesis concentrated in Shandong, Zhejiang, and Hubei provinces. Key quality considerations include enantiomeric purity, particle size distribution for feed-grade products, and stringent residual solvent control. KingWish supplies GMP-certified florfenicol meeting CVP and in-house standards validated against international pharmacopoeia requirements, supporting veterinary pharmaceutical and feed manufacturers worldwide.

Quality Specifications

Purity (HPLC)	≥ 98.0%, per CVP/IN HOUSE monograph
Related Substances	Thiamphenicol ≤0.5%; any individual impurity ≤0.5%; total ≤2.0%
Enantiomeric Purity	Chiral HPLC confirms single enantiomer; meets pharmacopoeia specifications for stereochemical purity
Residual Solvents	Methanol ≤ 3,000 ppm; ethyl acetate ≤ 5,000 ppm; per ICH Q3C
Heavy Metals	≤ 20 ppm (aquaculture-grade meets stricter limits per importing country requirements)
GMP Status	Manufactured under ICH Q7 GMP conditions

Veterinary Applications

Aquaculture (Feed Premix)

Florfenicol 10-50% feed premix. Fish: 10 mg/kg BW/day for 10 days for furunculosis, vibriosis, streptococcosis. Shrimp: medicated feed for Vibrio and NHP bacteria. Particle size critical for feed homogeneity.

Injectable (Cattle & Swine)

Florfenicol 300 mg/mL injectable solution. Cattle: 20 mg/kg IM (single dose) or 40 mg/kg SC for BRD. 28-day meat withdrawal. Swine: 15 mg/kg IM every 48h for respiratory disease.

Therapeutic Areas

Aquaculture: Furunculosis, vibriosis, streptococcosis, columnaris disease, edwardsiellosis
Cattle: Poultry respiratory disease (BRD), interdigital phlegmon
Swine: Respiratory disease, atrophic rhinitis, Glasser's disease
Poultry: Colibacillosis, infectious coryza, pasteurellosis

Frequently Asked Questions

Florfenicol is a broad-spectrum veterinary antibiotic used across three major sectors: aquaculture (fish and shrimp — furunculosis, vibriosis, streptococcosis via medicated feed), cattle (poultry respiratory disease caused by Mannheimia haemolytica, Pasteurella multocida, Histophilus somni), and swine (respiratory disease caused by Actinobacillus pleuropneumoniae, Pasteurella multocida). It is also used in poultry for colibacillosis and infectious coryza. Its ability to overcome chloramphenicol resistance via the fluorine substitution at the C-3 position makes it effective against strains resistant to older amphenicols.

Chloramphenicol was banned from food-animal use in the US (1985), EU (1994), and most regulated markets due to a rare but fatal idiosyncratic aplastic anemia risk in humans. Florfenicol was designed by Schering-Plough scientists to preserve the broad-spectrum activity of the amphenicol class while eliminating the safety concern. The key structural innovation was replacing the C-3 hydroxyl group of thiamphenicol with a fluorine atom. This fluorine substitution blocks the bacterial acetyltransferase enzyme that confers chloramphenicol resistance while simultaneously eliminating the p-nitro group of chloramphenicol — the moiety responsible for the aplastic anemia risk. Florfenicol thus has a fundamentally different safety profile that allowed its approval for food animals.

Three key differences: (1) Florfenicol has a fluorine atom at the C-3 position (versus a hydroxyl in thiamphenicol), which blocks enzymatic acetylation — the primary mechanism of bacterial resistance to amphenicols. This means florfenicol is active against many thiamphenicol-resistant strains. (2) Florfenicol has higher lipid solubility and better tissue penetration, particularly into the lungs, making it more effective for respiratory disease. (3) Florfenicol has a broader antibacterial spectrum — it covers some pathogens (e.g., certain Pasteurella and Mannheimia strains) at lower MICs than thiamphenicol. In regulatory terms, florfenicol is approved for use in food animals under defined MRLs and withdrawal periods, while chloramphenicol is prohibited.

For aquaculture-grade florfenicol, pay special attention to: (1) Particle size distribution — finer and more uniform particle sizes improve homogeneity in medicated feed and dissolution rate in water. (2) Enantiomeric purity — florfenicol has two chiral centers; the pharmacopoeia specifies enantiomeric purity requirements. (3) Heavy metals — aquaculture products may face stricter heavy metal limits depending on the importing country. (4) Residual solvents — verify ICH Q3C compliance; methanol and ethyl acetate are common process solvents. (5) For markets like the EU, confirm that the API supports the customer's MRL dossier. KingWish provides particle size data and full impurity profiles on every batch CoA.

Sourcing Florfenicol: Key Checks

Documentation

Request CoA with HPLC purity, enantiomeric purity (chiral HPLC), and related substances data. Thiamphenicol content is a key quality indicator — it should be well below 0.5%. For aquaculture, also request particle size distribution data.

Red Flags

Elevated thiamphenicol as an impurity (>0.5%) suggests incomplete fluorination during synthesis. High residual methanol or ethyl acetate indicates poor process control. Prices significantly below market — florfenicol synthesis is multi-step and has a real cost floor.

Packaging & Logistics

Standard: 25 KG/DRUM. Custom packaging and micronized grades available. Store at room temperature (15-30°C), protected from light. Standard lead time 4-8 weeks. Aquaculture-grade may require different packaging specifications.

Market Context

Global florfenicol market grows at 5-7% annually, led by aquaculture expansion in Asia-Pacific and Latin America. China accounts for >80% of API production. Supply has periodically tightened due to environmental enforcement in Chinese chemical provinces. Market report

Frequently Asked Questions

Florfenicol is a broad-spectrum veterinary antibiotic used across three major production sectors. In aquaculture , it is the dominant antibiotic for bacterial disease in finfish (salmon, tilapia, catfish, carp) and shrimp — treating furunculosis, vibriosis, streptococcosis, columnaris, and edwardsiellosis via medicated feed at 10 mg/kg BW for 10 days. In cattle , it is a first-line injectable for poultry respiratory disease (BRD) at 20-40 mg/kg, with excellent lung tissue penetration. In swine, it is used in veterinary anti-infective formulations. In poultry, it addresses colibacillosis and infectious coryza.

Chloramphenicol was banned from food-animal use in the US (1985), EU (1994), and most regulated markets due to a rare but fatal idiosyncratic aplastic anemia risk — approximately 1 in 25,000-40,000 patients — that was not dose-dependent and could not be predicted. Florfenicol was designed by Schering-Plough to solve two problems in one molecule: (1) Replace the p-nitro group of chloramphenicol (the moiety responsible for aplastic anemia) with a methylsulfonyl group, eliminating the human safety risk. (2) Replace the C-3 hydroxyl group with a fluorine atom, which blocks bacterial acetyltransferase — the primary resistance mechanism. The fluorine substitution is the structural key that makes florfenicol active against chloramphenicol-resistant strains while being safe for food animals with defined MRLs and withdrawal periods.

Three major differences: (1) Resistance profile: Florfenicol's C-3 fluorine atom blocks enzymatic acetylation — the primary amphenicol resistance mechanism — making it active against many thiamphenicol- and chloramphenicol-resistant strains. Thiamphenicol retains the C-3 hydroxyl and is susceptible to the same acetylation-based resistance. (2) Tissue distribution: The fluorine substitution increases lipid solubility, giving florfenicol superior lung penetration (lung-to-plasma ratio >1) and better intracellular penetration. This makes florfenicol more effective for respiratory disease. (3) Antimicrobial spectrum: Florfenicol shows lower MICs against key veterinary pathogens (Mannheimia haemolytica, Pasteurella multocida, Actinobacillus pleuropneumoniae) compared to thiamphenicol.

For aquaculture-grade florfenicol, five quality parameters require special attention: (1) Particle size distribution — finer, more uniform particles improve feed homogeneity and dissolution; specify your required D50 and D90 values. (2) Enantiomeric purity — florfenicol has two chiral centers; verify single-enantiomer purity by chiral HPLC. (3) Heavy metals — importing countries (EU, Japan, US) may enforce stricter limits for aquaculture products than for terrestrial livestock. (4) Thiamphenicol content — this is the key synthesis impurity indicator; should be ≤ 0.5%. (5) Microbial limits — verify TAMC/TYMC compliance with pharmacopoeia. KingWish provides particle size data and full impurity profiles on every aquaculture-grade batch CoA.

Standards: CVP, IN HOUSE | CAS: 73231-34-2 | Quality data verified against pharmacopoeia monograph COA and MSDS available | DrugBank | July 2026