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Enrofloxacin (ENR) is a fluoroquinolone antibiotic sold by the Bayer Corporation under the trade name Baytril. Enrofloxacin is currently approved by the FDA for the treatment of individual pets and domestic animals in the United States. In September 2005, the FDA withdrew approval of Baytril for use in water to treat flocks of poultry, as this practice was noted to promote the evolution of fluoroquinolone-resistant strains of the bacterium Campylobacter, a human pathogen.[3]

Enrofloxacin Structural Formulae.png
Clinical data
AHFS/Drugs.comInternational Drug Names
  • AU: B3
  • US: C (Risk not ruled out)
Routes of
Oral, subcutaneous injection, topical (ear drops)
ATCvet code
Legal status
Legal status
  • AU: S4 (Prescription only)
  • UK: POM (Prescription only)
Pharmacokinetic data
Bioavailability80% in dogs, 65-75% in sheep [1]
MetabolismRenal and non-renal[1]
Elimination half-life4–5 hours in dogs, 6 hours in cats, 1.5 - 4.5 hours in sheep.
ExcretionBile (70%); Renal (30%)[2]
CAS Number
PubChem CID
CompTox Dashboard (EPA)
ECHA InfoCard100.131.355 Edit this at Wikidata
Chemical and physical data
Molar mass359.4 g·mol−1
3D model (JSmol)

It is a bactericidal agent. The bactericidal activity of enrofloxacin is concentration-dependent, with susceptible bacteria cell death occurring within 20–30 minutes of exposure. Enrofloxacin has demonstrated a significant post-antibiotic effect for both Gram-negative and Gram-positive bacteria and is active in both stationary and growth phases of bacterial replication. Enrofloxacin is partially deethylated by CYP450 into the active metabolite ciprofloxacin, which is also a fluoroquinolone antibiotic.

Activity and susceptibility dataEdit

Enrofloxacin is a synthetic antibacterial agent from the class of the fluoroquinolone carboxylic acid derivatives. It has antibacterial activity against a broad spectrum of Gram-negative and Gram-positive bacteria. It is effective against:

Variable activity against:

Ineffective against:

The following data represent minimum inhibitory concentration ranges for a few medically significant bacterial pathogens:

  • Escherichia coli - 0.022 - 0.03 µg/ml
  • Staphylococcus aureus - 0.0925 - 64 µg/ml
  • Pseudomonas aeruginosa - 0.05 µg/ml


Usage in poultry.

Adverse effects/warningsEdit

Enrofloxacin was banned for poultry use in 2005.[4]

Overdosage/acute toxicityEdit

It is unlikely that an acute overdose of either compound would result in symptoms more serious than either anorexia or vomiting, but the adverse effects noted above could occur. Dogs receiving 10 times the labeled dosage rate of enrofloxacin for at least 14 days developed only vomiting and anorexia. Death did occur in some dogs when fed 25 times the labeled rate for 11 days, however.

  • Oral LD50: greater than 5000 mg/kg
  • Dermal LD50: greater than 2000 mg/kg
  • Inhalation LD50: greater than 3547 mg/m3 (4-hour exposure)
  • Eye effects: irritant; reversible in less than 7 days. In cats, it can produce sudden onset blindness when administered by injection, as it is retinotoxic.[citation needed]


The brown rot fungus Gloeophyllum striatum can degrade the fluoroquinolone enrofloxacin using hydroxyl radicals.[5]


  1. ^ a b Plumb DC. Enrofloxacin. Veterinary Drug Handbook, fifth edition.
  2. ^ "Archived copy". Archived from the original on 2014-01-06. Retrieved 2014-01-06.CS1 maint: archived copy as title (link)
  3. ^ "Archived copy". Archived from the original on 2007-02-10. Retrieved 2007-03-07.CS1 maint: archived copy as title (link)
  4. ^ Washington Post, April 30, 2005 FDA Calls Efforts For Bayer Illegal Lawmakers' Help for Drug Firm Tests Limits Dan Morgan and Marc Kaufman
  5. ^ Wetzstein HG; Schmeer N; Karl W (1997). "Degradation of the fluoroquinolone enrofloxacin by the brown rot fungus Gloeophyllum striatum: identification of metabolites". Applied and Environmental Microbiology. 63: 4272–81. PMC 168747. PMID 9361414.