Baytril® 100 (enrofl oxacin) Injectable Now Approved for Control of Colibacillosis Associated with Escherichia coli in weaned pigs and for Intramuscular Administration in swine
Introduction
Colibacillosis associated with E. coli is a serious threat to the swine industry, aff ecting
herds worldwide. Many normal pigs can be infected with potentially pathogenic E. coli, and nursing pigs can ingest pathogens from the skin and mammary glands of dams.
Whether pigs contract colibacillosis depends on several factors: virulence of the
pathogen, resistance to infection and environmental considerations.1
Diarrhea is one of the fi rst symptoms of colibacillosis. Ingested E. coli pathogens colonize
the small intestine, producing enterotoxins that can eventually cause excessive diarrhea.
This increases exposure of other penmates and can lead to weight loss.1
Young pigs in particular may lose as much as 40% of their body weight due to fl uid loss.
Dehydration and other disease-related complications can ultimately result in death.1
For use by or on the order of a licensed veterinarian.
The following studies show that
Baytril® 100 (enrofl oxacin) Injectable is eff ective for the
control of colibacillosis in groups or pens of weaned pigs where
colibacillosis associated with E. coli has been diagnosed, and that intramuscular
administration of Baytril 100 is both 1) eff ective as measured by its
bioequivalence to subcutaneous administration and 2) safe.
Objective
The objective of this study was to evaluate the eff ectiveness
of Baytril® 100 (enrofl oxacin) Injectable for the control of
naturally acquired colibacillosis associated with E. coli in
weaned pigs.
Materials and methods
This study was placebo-controlled and incorporated
randomization and blinding as bias control measures.
Study sites
This study was conducted fi ve separate times at four
facilities:
1. LFM Quality Laboratories, Inc., Terre Haute, IN, USA
2. Midwest Veterinary Services, Inc., Oakland, NE, USA
3. LFM Quality Laboratories, Inc., Terre Haute, IN, USA (two separate studies conducted here)
4. Thomas D. Morris, Inc., Reisterstown, MD, USA
5. Veterinary Resources, Inc., Ames, IA, USA
Animals
A total of 1500 weaned pigs were sourced from U.S.
commercial swine operations and enrolled across fi ve
studies at four sites (two studies were conducted at LFM
Quality Laboratories, Inc.). Each site consisted of 60 pens of
fi ve pigs (30 pens per treatment group). Prior to allocating
pigs to respective treatment groups and pens, a natural
onset of colibacillosis was induced in the candidate pig
population at each site by commingling candidate pigs
with a cohort of 30 to 75 “seeder pigs.” Seeder pigs were
previously confi rmed positive for beta-hemolytic E. coli and exhibited clinical signs of colibacillosis at the time of
commingling.
When a minimum of 5% of the candidate pigs were
considered clinically aff ected with colibacillosis, all candidate
pigs were individually scored for clinical signs of colibacillosis.
Eligible candidate pigs clinically aff ected with colibacillosis
and subclinical pigs were randomly allocated to 60 pens
(30 pens per treatment group) of fi ve pigs per pen and
administered the appropriately assigned treatment; this day
represented Study Day 0. Enrolled “study pigs” were between 16
and 33 days of age and weighed between 4.7 and 26.5 lbs on
Study Day 0 (day of treatment administration). Seeder pigs were
not enrolled in the study.
Treatments
At each study site, 150 pigs (30 pens of fi ve pigs) were enrolled
in each treatment group. Treatments were randomly assigned
to pens within blocks of two.
1. Baytril 100 — 7.5 mg enrofl oxacin/kg body weight
administered as a single dose intramuscularly
2. Saline (placebo) control — administered once
intramuscularly at the same volume as pigs receiving
Baytril 100
Study procedures
Pigs were injected intramuscularly with their assigned
treatment once on the day of enrollment (Study Day 0). Pigs
were observed at least once after treatment administration on
Study Day 0 for adverse events. General health observations
were conducted twice daily from Study Days 1 to 6 and once
on Study Day 7.
Pigs that became moribund due to colibacillosis and pigs
that developed conditions not related to colibacillosis were
removed and euthanized. Removals attributable to colibacillosis
were included in the fi nal analysis and considered treatment
failures whereas removals not attributable to colibacillosis were
removed from the fi nal analysis and not considered treatment
failures. On Study Day 7, all remaining enrolled pigs were
clinically scored for colibacillosis and weighed.
Pigs that met the following criteria were considered clinically
aff ected with colibacillosis:
A diarrhea score ≥ 2 on a severity scale of 0 (normal) to 3
A depression score ≥ 1 on a severity scale of 0 (normal)
to 3 and/or a gauntness score ≥ 1 on a severity scale of 0
(normal) to 2
Control of colibacillosis associated with Escherichia coli
Extra-label use in food-producing animals is prohibited.
Results
Taken as an average across all study sites, the overall
mean treatment success rate was signifi cantly higher
(P = 0.035) for the Baytril® 100 (enrofl oxacin) Injectable
group compared to the saline control group. N = 30 pens
per treatment, per study site.
The average mean treatment success rate was 61.5%
and 44.7% for the Baytril 100 and saline control groups,
respectively (Figure 1).
Baytril 100 body weight gains were signifi cantly greater
(P = 0.035) than the saline control body weight gains at all
study sites. N = 30 pens per treatment, per study site.
Mea
n tr
eatm
ent s
ucc
ess
rate
61.5%61 5%
44.7%
100% –
90% -
80% -
70% -
60% -
50% -
40% -
30% -
20% -
10% -
0% -
Baytril 100 Saline
Figure 1: Mean Percentage of Treatment Success — Average Across All Study Sites
Baytril 100 Saline
BWG (lbs) — Study 1 3.15 1.61
BWG (lbs) — Study 2 5.30 4.28
BWG (lbs) — Study 3 1.25 0.27
BWG (lbs) — Study 4 1.29 0.12
BWG (lbs) — Study 5 3.12 1.77
Total Average BWG (lbs)
2.82 1.61
Table 1: Mean Body Weight Gain (BWG) of Study Pigs by Treatment and Site
Special considerations
In a commercial setting, all pigs in an aff ected barn would
normally be treated for colibacillosis because of the high
transmission rate of E. coli. However, the study design*
required blocked allocation of Baytril 100-treated and saline-
treated pens, resulting in adjacent housing of treatment
groups. This likely caused transmission of E. coli between
treatment groups. Effi cacy was likely diminished in this test
system due to the high likelihood of reinfection of Baytril
100-treated pigs by adjacently housed untreated control pigs.
Given the above, higher effi cacy outcomes may be
observed under standard commercial swine management
practices. However, even in the face of 7 days of constant
disease pressure, Baytril 100 pigs consistently outgained
saline-treated pigs across all study sites (Table 1).
Statistical evaluation
One pen was the experimental unit. The percentage
of pigs with treatment success within each pen was
compared between the two treatment groups. Treatment
was considered successful if a pig met all of the following
criteria on Study Day 7:
A diarrhea score of ≤ 1
A depression score of 0
A gauntness score of ≤ 1
A total of 299 (of 300) enrolled pens were included in the
analysis. One pen was removed from the study and analysis
due to reasons not associated with colibacillosis. Percent
success and 95% confi dence intervals were used to
summarize the results.
Taken as an average across all study sites, mean body weight
gains from Study Day 0 to 7 were 2.82 and 1.61 lbs for the
Baytril 100 and saline control groups, respectively (Table 1).
Conclusions: Based upon the results of this study, Baytril 100 proved eff ective for the control of colibacillosis associated with E. coli in weaned pigs.
*Study design was agreed upon between the study Sponsor and Regulatory Agency.
Swine intended for human consumption must not be slaughtered within 5 days of receiving a single-injection dose.
Eff ectiveness of intramuscular administration
Objective
The objective of this study was to evaluate the
eff ectiveness of intramuscular administration of
Baytril® 100 (enrofl oxacin) Injectable* as measured
by its bioequivalence to subcutaneous administration.
Materials and methods
This study incorporated randomization as a bias
control measure.
Study site
1. Bayer HealthCare AG, Animal Health Division,
Leverkusen, Germany
Animals
A total of 32 healthy, male and female, German Landrace
Hybrid fattening pigs were used in the study. Of these, 28
were included in the determination of bioequivalence. Pigs
were approximately 4 months old and ranged in weight
from 115.7 to 142.2 lbs at the start of the study.
Pigs were housed in an indoor facility with each pen
containing two pigs of the same gender. Pigs were fed once
daily and allowed unlimited access to water.
Pigs were blocked by gender and randomly assigned to
pen and treatment using a randomization table. A clinical
examination was performed on Study Day -1 to ensure pigs
were healthy and acceptable for inclusion.
Treatments
Pigs were randomized to one of three treatment groups:
1. Baytril 100* IM — 7.5 mg enrofl oxacin/kg body
weight administered as a single dose
intramuscularly (N = 14)
2. Baytril 100* SC — 7.5 mg enrofl oxacin/kg body weight
administered as a single dose subcutaneously (N = 14)
3. Untreated control — no treatment given (N = 4)
Study procedures
Pigs in the two treatment groups were administered
7.5 mg Baytril 100*/kg body weight according to their
assigned administration route (IM or SC). Blood samples
were collected from each animal at 0 (pre-dose), 0.5, 1, 2,
4, 6, 8, 10, 12, 32, 48 and 72 hours after injection. Samples
were analyzed for serum enrofl oxacin concentrations to
determine bioequivalence.†
General health observations were also conducted
from Study Day -1 through Study Day 6, and a clinical
examination was performed on Study Day 6. Body weights
were recorded on Study Day -1 and Study Day 6.
Statistical evaluation
For the individual and combined analyses, drug
pharmacokinetics was quantifi ed via the use of a non-
compartmental analysis. The results of that analysis were
used in the estimation of the 90% confi dence limits about
the ratio of treatment means.
Clinical and general health observations
At study inclusion, fi ve pigs were noted to have bilateral
conjunctivitis, one pig had small nodules in the neck
region, and one pig had swellings on all four legs. These
pigs were considered within the defi nition of healthy
and were included in the study. One pig had a temporary
protrusion of the third eyelid and one pig had an abscess
in the right neck at 6 days post-injection. No other
abnormal observations were recorded during the post-
injection period.
For use by or on the order of a licensed veterinarian.
Results
Serum enrofl oxacin concentrations obtained after IM or
SC injection of Baytril® 100 (enrofl oxacin) Injectable* were
comparable (Figure 2).
Adverse reactions
No test-related adverse events were observed during
the study.
Extra-label use in food-producing animals is prohibited.
Conclusions: Based upon the results of this study, comparable
eff ectiveness will be achieved when Baytril 100* is
administered at a dose of 7.5 mg/kg by either SC or IM
injection into the neck of swine.
* This study used Baytril® Max 10% Injectable Solution, a formulation of enrofl oxacin identical to Baytril 100.
† Ciprofl oxacin concentrations were also measured, because enrofl oxacin metabolizes into ciprofl oxacin in the body. However, it is the parent compound (enrofl oxacin) as opposed to the metabolite (ciprofl oxacin) that typically provides the most sensitive treatment comparison. Therefore, for the purpose of this study, only the enrofl oxacin concentrations were considered (Figure 2).
Figure 2: Average Concentration-Time Profi le for Enrofl oxacin After IM or SC Administration
Mea
n En
rofl o
xaci
n Se
rum
Con
cent
ratio
n (u
g/L) Mean Concentration-Time Profi le for Enrofl oxacin
After IM or SC Administration (Mean ± SD)
0 10 20 30 40 50 60 70 80
Time (hours)
IM Mean Serum Concentration (ug/L) SC Mean Serum Concentration (ug/L)
2000
1500
1000
500
0
-500
Safety of intramuscular administration
Objective
The objective of this study was to evaluate the safety of
Baytril® 100 (enrofl oxacin) Injectable when administered
by intramuscular (IM) injection in weaned pigs at 1X, 3X
and 5X body weight.
Materials and methods
This placebo-controlled study incorporated randomization
as a bias control measure.
Study site
1. Midwest Veterinary Services, Inc., Oakland, NE, USA
Animals
Forty-eight healthy, crossbred, weaned pigs (24 females
and 24 intact males) were enrolled in this study. At study
initiation (Day 0), pigs were 20 to 22 days old and weighed
between 11.2 and 20.1 lbs. Pigs were housed in an
environmentally controlled room with unlimited access to
water and feed.
Treatments
Pigs were randomized to one of four treatment groups,
with equal numbers males and females in each group:
1. Baytril 100 1X dose — 7.5 mg enrofl oxacin/kg body
weight administered intramuscularly (N = 12)
2. Baytril 100 3X dose — 22.5 mg enrofl oxacin/kg
body weight administered intramuscularly (N = 12)
3. Baytril 100 5X dose — 37.5 mg enrofl oxacin/kg body
weight administered intramuscularly (N = 12)
4. Saline (placebo) control — administered
intramuscularly at the same volume as pigs receiving
37.5 mg Baytril 100/kg body weight (N = 12)
Study procedures
Pigs were dosed with their assigned treatment in the
neck on Study Days 0, 7 and 14. A maximum of 3 mL was
injected per injection site.
Body weights were recorded on Study Days -3 (or -2), -2 (or
-1), 6, 13 and 15. Clinical evaluations (attitude, locomotion,
respiration, abdominal fi ll, hydration, injection site and
adverse events) were conducted twice daily on Study Days
1 to 6 and Study Days 8 to 13; four times daily on Study
Days 0, 7 and 14; and once on Study Day 15.
Daily feed and water consumption was also measured
and blood, urine and fecal sample evaluations conducted.
Blood was collected to measure serum enrofl oxacin levels.
On Day 15, all pigs were humanely euthanized and a
complete necropsy was conducted.
Note: In order to facilitate data collection and necropsy,
“Study Day 0” was staggered by one calendar day for half
of the study pigs. This is why measurements before Study
Day 0 are shown as taking place on two days: e.g., Study
Day -3 (or -2).
Statistical evaluation
Measurements and observations include clinical and
physical evaluations; serum enrofl oxacin levels; daily feed
and water consumption; and blood, urine and fecal
sample evaluations.
All continuous variables were analyzed using a mixed
model analysis. Statistical comparisons of treatment eff ects
and comparison of treatment by time were performed at
the 0.1 level of signifi cance. Comparison of treatment by
time by sex was performed at the 0.05 level of signifi cance.
Swine intended for human consumption must not
be slaughtered within 5 days of receiving a single-
injection dose.
Results
A wide range of factors was considered in determining the
safety of IM administration of Baytril® 100 (enrofl oxacin)
Injectable. These results are summarized below.
Body weight increases were observed in all individual
pigs and in all treatment groups. Although not statistically
signifi cant, weight gain per treatment group was inversely
proportional to dose.
Daily feed and water consumption generally increased
in all treatment groups. However, each treatment was
associated with a transient (~72 hours), dose-related
decrease in feed and water consumption.
There were no mortalities or unscheduled removals.
Mild injection site swelling was recorded in one 5X pig after
the fi rst treatment, in two 5X pigs after the second treatment,
and in eight 5X pigs following the third treatment. Swelling
resolved without intervention within 24 to 48 hours of onset
(fi rst and second treatments). There were no other clinical
observations or abnormal physical examination fi ndings
related to administration of Baytril 100.
No clinically relevant test-related diff erences in blood
hematology or coagulation, urinalysis, or fecal analysis
parameters were detected. Serum concentrations of
some enzymes were statistically signifi cantly higher
(P = 0.10) in Baytril 100-treated groups compared to the
control group. These results were not considered to be
clinically relevant to safety because all pigs remained
clinically healthy during the study (other than injection
site swelling) and the elevations were consistent with
muscle damage related to injection site injury.
The only post-mortem fi ndings attributed to
administration of Baytril 100 were injection site lesions.
The appearance and location of lesions seemed
to correspond to day/site of injection and dose volume.
Pharmacokinetic evaluation showed minor
accumulation of enrofl oxacin or its active metabolite,
ciprofl oxacin, with a once-weekly dosing regimen. In the
3X and 5X dose groups, prolonged exposure to the drug
resulted in its remaining in the system longer
than predicted.
Conclusions:
Based upon the results of this study, IM injection of Baytril 100
is safe in swine when administered at a dose of 7.5 mg
enrofl oxacin/kg body weight in the neck.
For use by or on the order of a licensed veterinarian.
Dilution schedule now available
Baytril® 100 (enrofl oxacin) Injectable may now be diluted with sterile water prior to injection in smaller pigs. The diluted
product should be used within 24 hours. Store diluted solution in amber glass bottles between 4° – 40°C (36° – 104°F).
Dilution Schedule*
Swine Weight mL of Baytril 100 mL of sterile water Number of doses
10 lb 34 mL 66 mL 100
15 lb 51 mL 49 mL 100
20 lb 68 mL 32 mL 100
25 lb 85 mL 15 mL 100
Extra-label use in food-producing animals is prohibited.
*For 1 mL dose volume from diluted solution.
1Neumann EJ, Ramirez A, Schwartz KJ, eds. (2009). Swine Disease Manual. 4th edition. Published by AASV. Information accessed via: http://vetmed.
iastate.edu/vdpam/new-vdpam-employees/food-supply-veterinary-
medicine/swine/swine-diseases/colibacillosis-ecoli-. Accessed
November 19, 2014.
©2015 Bayer HealthCare LLC, Animal Health, Shawnee Mission, Kansas 66201
Bayer, the Bayer Cross, Baytril and Right the fi rst time are registered trademarks of Bayer
BL15317
Swine intended for human consumption must not
be slaughtered within 5 days of receiving a single-injection dose.