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Baytril Injectable Solution (Canada)

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Baytril Injectable Solution

This treatment applies to the following species:
Manufacturer: Bayer

(enrofloxacin)

Antimicrobial Injectable Solution

FOR VETERINARY USE ONLY

DIN 02169428

Description

Enrofloxacin is a synthetic chemo-therapeutic agent from the class of the quinolone carboxylic acid derivatives. It has antibacterial activity against a broad spectrum of Gram negative and Gram positive bacteria (see Table 1). It is rapidly absorbed from the digestive tract, penetrating into all measured body tissues and fluids (see Table 2). Each mL of injectable solution contains: enrofloxacin 50 mg, n-butyl alcohol 30 mg, potassium hydroxide for pH adjustment and water for injection, q.s.

CHEMICAL NOMENCLATURE: 1-cyclopropyl-7-(4-ethyl-1-piperazinyl)-6-fluoro-1,4-dihydro-4-oxo-3-quinolinecarboxylic acid.

ACTIONS:

Microbiology: Enrofloxacin, a 4-fluoroquinolone compound, is bactericidal with activity against a broad spectrum of both Gram negative and Gram positive bacteria.

Fluoroquinolones elicit their bactericidal properties through interactions with two intercellular enzymes - DNA gyrase (DNA topoisomerase II) and DNA topoisomerase IV - which are essential for bacterial DNA transcription, synthesis and replication. It is believed that fluoroquinolones actively bind with DNA:ENZYME complexes and thereby inhibit the essential processes catalyzed by the enzymes (DNA supercoiling and chromosomal decatenation)1. The ultimate outcome of fluoroquinolone intervention is DNA fragmentation and bacterial cell death.2,3

Enrofloxacin minimum inhibitory concentrations (MICs) were determined for canine and feline bacterial isolates originating from natural infections of the dermal, gastrointestinal, respiratory and urinary systems. Seven hundred and thirty-eight (738) isolates were collected from 14 different diagnostic laboratories located throughout the United States. Bacterial identity was confirmed by colony morphology, Gram stain and biochemical testing; for mycoplasmas, identity was confirmed by colony morphology and Dienes stain. The in vitro susceptibilities of all bacterial and mycoplasma isolates were determined by enrofloxacin microbroth dilution methods and the resultant enrofloxacin MIC50 and MIC90 values are presented in Table 1. In vitro susceptibility testing was performed in accordance with guidelines established by the National Committee for Clinical Laboratory Standards (NCCLS; Document M31-P, Volume 14, November 20).

Table 1 - MIC Values for Enrofloxacin Against Canine and Feline Pathogens (Diagnostic laboratory isolates, 1997)

Organism

Isolates

MIC50 (µg/ml)

MIC90 (µg/ml)

Bordetella spp.

25

0.5

0.5

Enterococcus spp.

40

1

2

Escherichia coli

138

0.03

0.06

Klebsiella pneumoniae

32

0.06

0.12

Mycoplasma spp.

76

0.25

0.5

Pasteurella spp.

16

0.015

0.03

Proteus spp.

88

0.12

0.25

Pseudomonas aeruginosa

69

1

8

Salmonella spp.

15

0.06

0.25

Staphylococcus intermedius

119

0.12

0.25

Staphylococcus spp.

120

0.12

0.25

Distribution in the Body: Enrofloxacin penetrates into all canine tissues and body fluids. Concentrations of drug equal to or greater than the MIC for many pathogens (See Tables 1 and 2) are reached in most tissues by two hours after dosing at 2.5 mg/kg and are maintained for 8-12 hours after dosing. Particularly high levels of enrofloxacin are found in urine. A summary of the body fluid/tissue drug levels at 2 to 12 hours after dosing at 2.5 mg/kg is given in Table 2.

Table 2 - Body Fluid/Tissue distribution of Enrofloxacin in Dogs Single Oral Dose = 2.5 mg/kg (1.13 mg/lb)

Body Fluids (mcg/mL)

Post-treatment Enrofloxacin Levels

Canine (n=2)

2 Hr.

8 Hr.

Urine

43.05

55.35

Eye Fluids

0.53

0.66

Whole Blood

1.01

0.36

Plasma

0.67

0.33

Tissues (mcg/g) Hematopoietic System

Liver

3.02

1.36

Spleen

1.45

0.85

Bone Marrow

2.10

1.22

Lymph Node

1.32

0.91

Urogenital System

Kidney

1.87

0.99

Bladder Wall

1.36

0.98

Testes

1.36

1.10

Prostate

1.36

2.20

Uterine Wall

1.59

0.29

Gastrointestinal and Cardiopulmonary System

Lung

1.34

0.82

Heart

1.88

0.78

Stomach

3.24

2.16

Small Intestine

2.10

1.11

Other

Fat

0.52

0.40

Skin

0.66

0.48

Muscle

1.62

0.77

Brain

0.25

0.24

Mammary Gland

0.45

0.21

Feces

1.65

9.97

Pharmacokinetics: In dogs, the absorption and elimination characteristics of the oral formulation are linear (plasma concentrations increase proportionally with dose) when enrofloxacin is administered at up to 11.5 mg/kg, twice daily.4 Approximately 80% of the orally administered dose enters the systemic circulation unchanged. The eliminating organs, based on the drug’s body clearance time, can readily remove the drug with no indication that the eliminating mechanisms are saturated. The primary route of excretion is via the urine. The absorption and elimination characteristics beyond this point are unknown. Saturable absorption and/or elimination processes may occur at greater doses. When saturation of the absorption process occurs, the plasma concentration of the active moiety will be less than predicted, based on the concept of dose proportionality.

Following an oral dose in dogs of 2.5 mg/kg (1.13 mg/lb), enrofloxacin reached 50% of its maximum serum concentration in 15 minutes and peak serum level was reached in one hour. The elimination half-life in dogs is approximately 2 1/2-3 hours at that dose.

A graph indicating the mean serum levels following a dose of 2.5 mg/kg (1.13 mg/lb) in dogs (oral and intramuscular) and cats (oral) is shown in Figure 1.

Figure 1 - Serum Concentrations of Enrofloxacin

Following a Single Oral or Intramuscular Dose at 2.5 mg/kg in Dogs and a Single Oral Dose at 2.5 mg/kg in Cats.

Breakpoint: Based on in-vitro susceptibility, pharmacokinetics and clinical response, the following breakpoints are recommended for canine isolates. These breakpoints have been approved by the National Committee for Clinical Laboratory Standards (NCCLS) and are published in NCCLS document M-31:

Zone Diameter (mm)

MIC µg/mL

Interpretation

≥ 23

≤ 0.5

Susceptible (S)

18 - 22

1 - 2

Flexible Label (F)

≤ 17

≥ 4

Resistant (R)

A report of ‘Susceptible’ indicates that the pathogen is likely to be inhibited by plasma levels generally attained with the lower end of the dose range (2.5 mg/kg BW twice daily or 5.0 mg/kg BW once daily). A report of ‘Flexible Label’ indicates that the pathogen is likely inhibited by plasma levels attained with adherence to the principles of FDA-approved Professional Flexible Labeling in dogs. With enrofloxacin, conditions due to ‘F’ bacteria can be treated successfully by administration of an intermediary dose within the lower (>5.0 mg/kg BW once daily) and upper (≤ 20 mg/kg BW once daily) limits of the approved flexible dose range.

Determination of the precise dosage is based upon a careful assessment of the interrelationships amongst host (immunocompetency, stress, site of infection, etc.), pathogen (virulence, MIC, emerging resistance, etc.) and chemotherapeutic (dose-dependent vs time-dependent efficacy, postantibiotic effects, toxicity etc.). A report of ‘Resistant’ indicates that the pathogen is unlikely to be inhibited by plasma levels attained with administration of the highest approved dose (20 mg/kg BW once daily) and alternative antimicrobial therapy should be selected.

Standardized procedures require the use of laboratory quality control organisms for both standardized disk diffusion assays and standardized dilution assays. The 5 µg enrofloxacin disk should give the following zone diameters and enrofloxacin powder should provide the following MIC values for reference strains. The indicated ranges for quality control organisms are NCCLS-approved.

QC Strain

Zone Diameter (mm)

MIC µg/mL

E. coli ATCC 25922

32 - 40

0.008 - 0.03

P. aeruginosa ATCC 27853

15 - 19

1 - 4

S. aureus ATCC 25923

27 - 31

---

S. aureus ATCC 25913

---

0.03 - 0.12

Baytril Injectable Solution Indications

Dogs: Baytril® (enrofloxacin) antibacterial injectable solution is indicated for the management of diseases in dogs associated with bacteria susceptible to enrofloxacin.

EFFICACY CONFIRMATION:

Dogs: Clinical efficacy was established in dermal infections (wounds and abscesses) associated with susceptible strains of Escherichia coli, Klebsiella pneumoniae, Proteus mirabilis, and Staphylococcus intermedius; respiratory infections (pneumonia, tonsillitis, rhinitis) associated with susceptible strains of Escherichia coli and Staphylococcus aureus;  and urinary cystitis associated with susceptible strains of Escherichia coli, Proteus mirabilis, and Staphylococcus aureus.

Contraindications

Enrofloxacin is contraindicated in dogs known to be hypersensitive to quinolones.

Dogs: Based on the studies discussed under the section on Animal Toxicology, the use of enrofloxacin is contraindicated in small and medium breeds of dogs during the rapid growth phase (between 2 and 8 months of age). The safe use of enrofloxacin has not been established in large and giant breeds during the rapid growth phase. Large breeds may be in this phase for up to one year of age and the giant breeds for up to 18 months. In clinical field trials utilizing a daily oral dose of 5.0 mg/kg, there were no reports of lameness or joint problems in any breed. However, controlled studies with histological examination of the articular cartilage have not been conducted in the large or giant breeds.

Adverse Reactions

Post Approval Experience: The following adverse experiences, although rare, are based on voluntary post-approval adverse drug experience reporting. The categories of reactions are listed in decreasing order of frequency by body system.

Gastrointestinal: Anorexia, diarrhea, vomiting, elevated liver enzymes

Neurologic: ataxia, seizures

Behavioral: Depression, lethargy, nervousness

ANIMAL TOXICOLOGY:

Adult dogs receiving enrofloxacin orally at a daily dosage rate 52 mg/kg for 13 weeks had only isolated incidences of vomition and inappetence. Adult dogs receiving the tablet formulation for 30 consecutive days at a daily treatment of 25 mg/kg did not exhibit significant clinical signs nor were there effects upon the clinical chemistry, hematological or histological parameters. Daily doses of 125 mg/kg for up to 11 days induced vomition, inappetence, depression, difficult locomotion and death while adult dogs receiving 50 mg/kg/day for 14 days had clinical signs of vomition and inappetence.

Adult dogs dosed intramuscularly for three treatments at 12.5 mg/kg followed by 57 oral treatments at 12.5 mg/kg, all at 12 hour intervals, did not exhibit either significant clinical signs or effects upon the clinical chemistry, hematological or histological parameters.

Oral treatment of 15 to 28 week old growing puppies with daily dosage rates of 25 mg/kg has induced abnormal carriage of the carpal joint and weakness in the hindquarters. Significant improvement of clinical signs is observed following drug withdrawal. Microscopic studies have identified lesions of the articular cartilage following 30 day treatments at either 5, 15 or 25 mg/kg in this age group. Clinical signs of difficult ambulation or associated cartilage lesions have not been observed in 29 to 34 week old puppies following daily treatments of 25 mg/kg for 30 consecutive days nor in 2 week old puppies with the same treatment schedule.

Tests indicated no effect on circulating microfilariae or adult heartworms (Dirofilaria immitis) when dogs were treated at a daily dosage rate of 15 mg/kg for 30 days. No effect on cholinesterase values was observed.

No adverse effects were observed on reproductive parameters when male dogs received 10 consecutive daily treatments of 15 mg/kg/day at 3 intervals (90, 45 and 14 days) prior to breeding or when female dogs received 10 consecutive daily treatments of 15 mg/kg/day at 4 intervals; between 30 and 0 days prior to breeding, early pregnancy (between 10th & 30th days), late pregnancy (between 40th & 60th days), and during lactation (the first 28 days).

DRUG INTERACTIONS:

Concomitant therapy with other drugs that are metabolized in the liver may reduce the clearance rates of the quinolone and the other drug.

Enrofloxacin has been administered to dogs at a daily dosage rate of 10 mg/kg concurrently with a wide variety of other health products including anthelmintics (praziquantel, febantel, sodium disophenol), insecticides (fenthion, pyrethrins), heartworm preventatives (diethylcarbamazine) and other antibiotics (ampicillin, gentamicin sulfate, penicillin, dihydrostreptomycin). No incompatibilities with other drugs are known at this time.

Baytril Injectable Solution Caution

Quinolone-class drugs should be used with caution in animals with known or suspected Central Nervous System (CNS) disorders. In such animals, quinolones have, in rare instances, been associated with CNS stimulation which may lead to convulsive seizures.

Quinolone-class drugs have been associated with cartilage erosions in weight-bearing joints and other forms of arthropathy in immature animals of various species.

Warnings

To limit the potential development of antimicrobial resistance:

- fluoroquinolone drugs such as Baytril® injectable solution 50 mg/mL should not be used indiscriminately.

- Baytril injectable solution 50 mg/mL should not be used in food producing animals.

Keep out of reach of children. Read package insert carefully for complete details.

Baytril Injectable Solution Dosage And Administration

The optimum dose of Baytril® (enrofloxacin) injectable solution has been established at 2.5 mg/kg (1.13 mg/lb) of body weight administered twice daily (every 12 hours). Baytril® Injectable Solution (5%) may be used in dogs twice daily (every 12 hours) by intramuscular injection for up to three days (6 doses). Different injection sites must be used for each treatment. Twelve hours following the last injection dosing should continue with Baytril® Tablets given once daily for 2-3 days beyond the cessation of clinical signs. Total treatment time with Baytril should not exceed 30 days. If no improvement is seen within five days, the diagnosis should be re-evaluated and a different course of therapy considered.

Storage

Protect from direct sunlight. Do not freeze and do not store above 40°C.

How Supplied

Baytril® Injectable Solution 50 mg/mL

Code Number

Vial Size

2685

50 mL

References

1 Hooper DC and Wolfson JS. Mechanisms of quinolone action and bacterial killing, in Quinolone Antimicrobial Agents. Washington DC, American Society for Microbiology, 2nd ed., 1993, 53-75.

2 Gootz TD and Brighty KE. Fluoroquinolone antibacterials: sar, mechanism of action, resistance and clinical aspects. Medicinal Research Reviews 1996; 16(5): 433-486.

3 Drlica K and Zhoa X. DNA gyrase, topoisomerase IV and the 4 quinolones. Microbiology and Molecular Biology Reviews 1997; 61(3): 377-392.

4 Walker RD et al. Pharmacokinetic evaluation of enrofloxacin administered orally to healthy dogs. American Journal of Veterinary Research 1992; 53(12): 2315-2319.

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Bayer Inc., 2920 Matheson Blvd East, Mississauga, ON., L4W 5R6

Bayer Revised: April 23, 2015 Version: 3.2

CPN: 1223006.3

BAYER
Animal Health

2920 MATHESON BOULEVARD EAST, MISSISSAUGA, ON, L4W 5R6
Telephone:   905-282-5550 or 800-62BAYER (800-622-2937)
Technical Service:   888-663-5326
Technical Services Email:   vetservicescanada@bayer.com
Order Desk:   800-387-9179
Order Desk Fax:   800-361-3306
Fax:   905-282-5725
Website:   www.animalhealth.bayer.ca
Every effort has been made to ensure the accuracy of the Baytril Injectable Solution information published above. However, it remains the responsibility of the readers to familiarize themselves with the product information contained on the Canadian product label or package insert.

Copyright © 2016 North American Compendiums. Updated: 2016-10-31

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