Open Journal of Veterinary Medicine, 2013, 3, 289-296
http://dx.doi.org/10.4236/ojvm.2013.36047 Published Online October 2013 (http://www.scirp.org/journal/ojvm)
Field Comparison of the Impact of Different Treatment
Durations in the Treatment of Acute Otitis Externa
in the Dog
Erik Grandemange1, Florence Pillet2, Olivier Roy2, Frédérique Woehrlé1
1Vétoquinol Research Centre, Lure Cedex, France
2CEBIPHAR, 1 rue de la Bodinière, Fondettes, France
Received June 27, 2013; revised July 27, 2013; accepted August 17, 2013
Copyright © 2013 Erik Grandemange et al. This is an open access article distributed under the Creative Commons Attribution Li-
cense, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
ABSTRACT
Background: Acute otitis externa is a common multi-factorial disorder in the dog. Several topical preparations are
available on the veterinary market, which are licensed for an either specified duration of treatment or for a discretionary
period that is determined by the clinician. Objectives: To compare the efficacy of two topical products, both licensed
for the treatment of otitis externa in the dog, but with different treatment durations. Animal Population: One hundred
and sixty dogs were enrolled in this multicentre field study from which 157 dogs were analysed in the Per Protocol sam-
ple (73 Aurizon® treated animals and 84 Easotic® treated animals). Method: Dogs were randomly assigned to Aurizon® or
Easotic® treatment groups. Aurizon® (Vétoquinol SA: marbofloxacin, clotrimazole, dexamethasone) was administered
daily in the affected ear(s) for 7 or 14 days, and was compared with a daily administration of Easotic® (Virbac SAS:
gentamicin, miconazole, hydrocortisone aceponate) for 5 days. General and localised clinical signs were scored on days
0 (D0), 3 (D3), 7 (D7), 14 (D14) and 21 (D21). Results: Clinical cure rates at the end of treatment were 56.3% and
48.8% (p = 0.35) in the Aurizon® and Easotic® groups respectively and 81.2% versus 74.7% one week after completing
the course of treatment (p = 0.34). Twenty-one days after initially presenting for the study, cure rates were 84.3% in the
Aurizon® group and 73.8% in the Easotic® (p = 0.12). A relationship between severity of clinical signs and treatment
duration was observed. Conclusion and Clinical Significance: At the end of the trial period, cure rates showed a ten-
dency to be higher in the Aurizon® treated animals. The flexible dosage and the veterinary monitoring permitted treat-
ment duration to be adjusted based upon the severity of otitis externa thus increasing the likelihood of clinical cure.
Keywords: Acute Otitis Externa; Topical Ear Treatment; Efficacy; Field Clinical Trial
1. Introduction
Acute otitis externa is a common pathology seen on a
daily basis in small animal practice (8.7%, Masuda et al.
[1]) and is characterized by acute inflammation of the
epithelium of the external auditory canal, often associ-
ated with an increase in cerumen production. Head shak-
ing, pruritis and other behaviours suggestive of aural pain
are also common features [2]. When otitis externa is
suspected, typical diagnostic procedures include a gen-
eral clinical examination followed by otoscopic inspec-
tion of the ear canal and the collection of aural exudates
for cytology and/or culture and sensitivity testing [3].
Potential primary causes of otitis externa include foreign
bodies; ectoparasites; dermal hypersensitivity; keratinisa-
tion defects; endocrinopathies; autoimmune disease and
neoplasia. Otitis externa, regardless of aetiology may be
exacerbated by factors such as abnormally stenotic or
torturous ear canals, pendulous pinnae, excessive mois-
ture or trauma of the ear [4-6]. Even though bacteria and
yeast are rarely primary causes, they are commonly iso-
lated (alone or in combination) in cases of otitis externa.
Malassezia pachydermatis, Staphylococcus pseudinter-
medius and Pseudomonas aeruginosa are particularly
common microbiological isolates and play a role in per-
petuating otitis externa [1,7-10]. Treatment of this condi-
tion consists of identifying and addressing both primary
and predisposing factors; cleaning the ear canal; ad-
dressing secondary infection with topical therapy (with
adjunctive systemic therapy where necessary); client
education; follow up; preventive and maintenance ther-
apy (where required) [3,11,12]. In cases where parasitic
infection has been excluded by cytologic examination
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opyright © 2013 SciRes. OJVM

E. GRANDEMANGE ET AL. 290
[13], the majority of topical treatments indicated for the
treatment of otitis externa combine an antimicrobial
agent with an antifungal agent and a glucocorticoid, the
latter component providing rapid symptomatic relief and
accelerating resolution of inflammation [14]. The li-
censed treatment duration of most products is often at
least 7 days, which may be extended to 2 or 3 weeks un-
der certain circumstances. Boda et al. [15] compared the
licensed treatment protocol of a new ear treatment (Ea-
sotic®, Virbac, 1 pump application per day, 5 day course
of treatment) to the one of a reference product (Surolan®,
Janssen, 3 - 5 drops applied twice daily for 7 days) and
concluded that simplifying dosing regimen and method
of administration improved owner compliance when
treating canine otitis externa. The authors reported satis-
faction rates but did not comment upon clinical response.
In a previous study [16], a comparison of clinical resolu-
tion following Aurizon® and Surolan® therapy demon-
strated a trend for better results in the Aurizon® treated
animals. The aim of this study was to compare the effi-
cacy of two therapeutic options for the treatment of otitis
externa in dogs that have different treatment durations:
Easotic® (5 days) versus Aurizon® (7 or 14 days of treat-
ment dependant on clinical response).
2. Materials and Methods
2.1. Experimental Design
This was a randomised, parallel controlled, multi-centre
study, conducted in compliance with VICH (International
Cooperation on Harmonisation of Technical Require-
ments for Registration of Veterinary Medicinal Products)
guidelines for Good Clinical Practice [17] and involved
twenty one French veterinary practices. The study con-
formed to local animal welfare standards and informed
consent was obtained from the owners of all participating
dogs. Microbiological analysis of samples collected fol-
lowing otoscopic examination was performed by a single
reference laboratory. For the purposes of assessing gen-
eral clinical condition and response to treatment, the ex-
perimental unit was the patient. The ear was the design-
nated experimental unit for the evaluation of local clini-
cal signs evaluation (some dogs suffered from bilateral
otitis at the time of inclusion in the study).
2.2. Selection of Animals
One hundred sixty animals were recruited from 21 vet-
erinary practices throughout France. Twelve of these
patients were examined at breeding sites and 148 at the
practice premises. Animals were included in the trial
based upon the following criteria:
 Good general physical condition on the basis of a
clinical examination
 Presented to the clinician with acute uni- or bilateral
otitis externa with fungal or bacterial involvement.
◦ Presence of moderate/severe inflammation of the
external acoustic meatus with moderate/severe
aural discharge (pus and/or cerumenous material).
The assessment score was >2 for both parameters
(for at least one ear in cases with bilateral in-
volvement).
◦ Chronic/recurrent cases of otitis externa and those
associated with ectoparasite infestation were ex-
cluded.
 No constraints were placed upon signalment, origin or
home environment.
2.3. Clinical Examination
Each animal was assessed over the course of three weeks
(21 days). The study calendar is presented in Table 1.
2.4. Laboratory Examination
The investigator collected a sample from the ear at D0
(prior to treatment only one ear was sampled even in
cases of bilateral disease). Samples were stored between
Table 1. Individual calendar.
DAY EVENT DAY EVENT
D0
Clinical examination and inclusion/non
inclusion criteria check.
Informed consent obtained from owner
Sample obtained from ear for microbiological analysis.
First administration of the study treatment.
D7
Clinical examination.
Clinician given the option to extend the treatment
period with Aurizon®.
If no further treatment required, sample obtained
from ear for microbiological analysis.
D1, D2 Application of treatment by the owner once daily. D7 to D13Application of treatment by the owner once daily
(animals receiving extended Aurizon® therapy).
D3 Local and general clinical examination.
Treatment compliance check. D14 + 1Clinical examination. Sample obtained from ear for microbiological analysis (all patients)
D3, D4 Application of treatment by the owner once daily.
D4: End of treatment with Easotic®. D21 ± 1
Clinical examination.
Owner assessment of response obtained.
Sample obtained from ear for microbiological analysis
(animals receiving extended Aurizon® therapy).
D5, D6 Application of treatment by the owner once daily
(Aurizon® group only).

E. GRANDEMANGE ET AL. 291
+2˚C and +8˚C pending shipment at ambient temperature
to the laboratory within 72 hours. Staphylococcus pseu-
dintermedius, Pseudomonas aeruginosa, Escherichia coli,
Proteus mirabilis, beta-haemolytic streptococci, Malas-
sezia pachydermatis and other yeasts than Malassezia
pachydermatis were identified if present.
2.5. Treatment Administration
Dogs were allocated to one of the two treatment groups
according to the randomisation list. Prior to initiating
treatment, an otoscopic examination was performed to
confirm the integrity of the tympanic membrane and to
ensure that there was no ectoparasite involvement. Prior
to each application of trial therapy, the external ear canal
was cleaned with Otifree® (Vétoquinol SA, France) and
dried. This procedure was performed by the clinician for
the first application; subsequent daily cleaning was the
responsibility of the pet owner for the remainder of the
trial period.
Trial products were administered topically to the ex-
ternal auditory canal of the affected ear(s) as follows:
 Aurizon® (Vétoquinol SA, France): a single admini-
stration of 10 drops once daily for 7 days (D0 to D6).
At D6, the clinician could extend treatment by further
7 days if they considered additional therapy was re-
quired (D7 to D13).
 Easotic® (VIRBAC SAS, France): a single admini-
stration of 1ml (one actuation of the dosing pump)
once daily for 5 days (D0 to D4).
2.6. Assessment Criteria
Patient assessment during the study consisted of a full
clinical examination by the investigator to obtain scores
for selected local and general parameters. These values
were processed to provide a General Clinical Score (GCS)
and a Local Clinical Score per ear (LCS) for each patient
(Table 2).
At D7, D14 + 1 and D21 ± 1, the clinical response of
each patient was characterised as follows:
 Cured:
-All local parameters scored  1 for each treated ear
and the Local Clinical Score < 3, and absence of itching
from auricular origin,
-General Clinical Score at end of treatment (D7 or D14)
less than the GCS at D0.
 Failure:
-Lack of improvement in local or clinical parameters,
relapse following an initial improvement or a worsening
of the condition that necessitated alternative therapy.
2.7. Statistical Analysis
Statistical analysis of results was performed using “Stat-
view” software (version 5.0, SAS Institute Inc., USA,
1992-1998). The primary criterion was clinical cure rate
at the end of treatment (D7 or D14), one week after
treatment was discontinued (D14 or D21) and on D21 for
all animals. Cure rates were compared using a Chi-square
test. The progression of clinical signs over time was the
secondary efficacy criteria.
Table 2. Clinical parameters.
General parameters (summarized by a general clinical score) (GCS)
 General behaviour
0 = Normal
1 = Subdued
2 = Depressed
 Appetite
0 = Normal
1 = Slightly decreased (<50%)
2 = Strongly decreased (>50%)
 Locomotion (excepting musculoskeletal disease)
0 = Normal
1 = Slightly abnormal
2 = Ataxic
 Head carriage
0 = Normal
1 = Slightly modified
2 = Abnormal
 Pruritis (ext ernal auditory meatus and/or pinna)
0 = Absent
1 = Intermittent, low-intensity
2 = Frequent, high-intensity
Local parameters (summarized by a local clinical score, LCS)
 Pinna lesions
0 = Absent
1 = Present
 Malodour
0 = Absent
1 = Present
 Pain on handling
0 = Absent
1 = Slight
2 = Moderate
3 = Severe
 Inflammation of external acoustic meat us
0 = Absent
1 = Slight
2 = Moderate
3 = Severe
 Exudate quantity
0 = Nil
1 = Slight
2 = Moderate
3 = Severe
 Exudate character
Ceruminous
Purulent

E. GRANDEMANGE ET AL. 292
Data obtained from the study were analysed as fol-
lows:
 Mean, standard deviation, minimum and maximum
age and body weight at date of inclusion (D0) was
calculated for animals in each treatment group. These
parameters were compared between groups using a
one-way analysis of variance. Distribution of patient
sex was compared using a Chi-square test.
 General and local clinical scores at inclusion were
described for each treatment group; the distributions
of unilateral versus bilateral otitis and suppurative
versus erythemato-ceruminous otitis at D0 were
compared using a Chi-square test. Rectal temperature
prior to the initiation of treatment was compared be-
tween groups using a one-way analysis of variance.
Clinical progression of the cases was compared using
an analysis of variance for repeated measurements, with
time and treatment-time-interaction designated as the
within-subject effects and the therapy utilised assigned to
the between-subject effect. To account for significant
interaction between time and treatment, a comparison
was carried out at each re-examination interval (D3, D7,
D14 and D21). In order to preserve sample size, any
missing values were replaced using the last observation
carried forward (LOCF) approach.
The type I error rate was set to 5% two-sided for all
comparisons, i.e. α = 0.05.
3. Efficacy Results
3.1. Evaluation and Completion of Dogs
Three enrolled animals were removed (two lost to follow
up and one where the owner did not comply with treat-
ment protocols). A total of 157 dogs (73 Aurizon®
treated animals and 84 Easotic® treated animals) was
kept in the Per Protocol analysis. The distribution of dogs
across treatment groups at inclusion was comparable
based upon demographics (Table 3) and clinical signs
(Table 4), although patients within the Aurizon® treat-
ment group tended to present with a higher GCS at the
time of enrolment. Thirty dogs with bilateral otitis were
enrolled per group and the total number of ears treated
was 103 in the Aurizon® group and 114 in the Easotic®
group. Otitis externa was characterised as suppurative in
63 ears (29 within the Aurizon® group, 34 in the Easotic®
group) and erythemato-ceruminous in 154 ears (74 ears
in the Aurizon® group, 80 in the Easotic® group). Bacte-
riological findings prior to treatment are presented in
Table 5.
3.2. Efficacy Assessments
No significant difference (p > 0.05) in treatment efficacy
was found at any point during the study, although a trend
in favour of better results was encountered in animals
treated with Aurizon® (p = 0.12 on D21, Figure 1). A
similar trend was also present for the rate of animals for
which a new auricular therapy was to be performed (13
within the Easotic® group versus 9 Aurizon® treated
animals; not statistically significant). A sub-analysis,
which took into account Aurizon® treatment duration,
suggested that there were two subpopulations enrolled
within this group. Furthermore, there appeared to be a
positive clinical correlation between the severity of
clinical signs at inclusion and the duration of treatment
chosen by the clinician. This relationship was observed
for GCS (Figure 2) but was absent for LCS (Figure 3).
3.3. Safety Assessments
Only one adverse event was detected during the course of
the study. One Easotic® treated animal was presented as
an emergency on D12 with ataxia and epileptiform sei-
zures. A hepatic tumour was diagnosed based on the re-
sults of imaging studies (ultrasonography); the owner
subsequently elected for euthanasia of the patient. No
causative link with the treatment was suspected.
4. Discussion
Blind conditions could not be implemented within this
Table 3. Demographic summary.
Aurizon® Easotic® Total
Number of animals 73 84 157
Age* (years) 6.6 ± 3.79
(min: 0.5; max: 15.7)
6.5 ± 3.79
(min: 0.3; max: 16.0)
6.5 ± 3.78
(min: 0.3; max: 16.0)
Body weight* (kg) 17.5 ± 11.14
(min: 4.0; max: 48.0)
20.7 ± 13.23
(min: 3.6; max: 72.0)
19.2 ± 12.37
(min: 3.6; max: 72.0)
Sex 42 females (11 neutered) and
31 males (5 neutered)
43 females (20 neutered) and
41 males (6 neutered)
85 females (31 neutered) and
72 males (11 neutered)
Otitis (affected ears)
Erythemato-ceruminous
Suppurative
103
74
29
114
80
34
217 ears
154 ears
63 ears
Breed The main pure breeds were Labrador retriever (n = 17), poodle (n = 13), golden retriever (n =8),
cocker spaniel (n = 8) and bull terrier (n = 8)

E. GRANDEMANGE ET AL. 293
Table 4. Clinical scores at inclusion.
Aurizon® Easotic®
Appetite (score) 0: 91.8%
1: 8.2%
0: 96.4%
1: 3.6%
Behaviour (score) 0: 93.2%
1: 6.8%
0: 97.6%
1: 2.4%
Locomotion (score) 0: 97.3%
1: 2.7%
0: 97.6%
1: 2.4%
Head carriage (score)
0: 68.5%
1: 27.4%
2: 4.1%
0: 76.2%
1: 21.4%
2: 2.4%
Pruritis (score)
0: 5.5%
1: 42.5%
2: 52.0%
0: 5.9%
1: 39.3%
2: 54.8%
Pinnal lesions (score) 0: 31.1%
1: 68.9%
0: 26.3%
1: 73.7%
Malodour (score) 0: 31.1%
1: 68.9%
0: 28.9%
1: 71.1%
Pain on handling (score)
0: 2.9%
1: 19.4%
2: 42.7%
3: 35.0%
0: 7.9%
1: 23.7%
2: 44.7%
3: 23.7%
Inflammation of external meatus (score) 2: 57.3%
3: 42.7%
2: 49.1%
3: 50.9%
Exudate quantity (score) 2: 57.3%
3: 42.7%
2: 50.9%
3: 49.1%
Table 5. Microbiological results prior to treatment and
clinical characterization of otitis.
Number of ears concerned
Pathogens Suppurative
otitis
Erythemato-ceruminous
otitis
Number of ear sampled 49 108
Staphylococcus
pseudintermedius 26 36
Streptococcus canis 12 2
Pseudomonas aeru gi n os a 9 3
Escherichia coli 3 0
Proteus mirabilis 3 0
Staphylococcus aureus 1 0
Streptococcus dysgalactiae
spp equisimilis 1 0
Malassezia pachydermatis 30 65
Other yeasts 0 3
study due to differences in the presentation of the treat-
ments and non-conformity of the licensed durations of
therapy.
The pathogens isolated from clinically affected ears at
inclusion were typical of those described in the literature
and the breeds of dog enrolled in the study were varieties
generally considered to have a predisposition for otitis
externa (e.g. Labrador, Golden Retriever, Poodle and
Cocker Spaniel) [4,5,8].
An ear cleaning was performed prior to administration
of topical therapy in order to remove ear wax and/or pu-
rulent material. The primary endpoint for the study was
clinical resolution of otitis externa as this was considered
to be a more common indicator of treatment success than
microbiological cure for the vast majority of owners and
clinicians within general practice.
The results of this multicentre field study confirmed
that Aurizon® is an effective treatment of otitis externa
with 84.3% of cure rate on D21, which confirmed previ-
ous findings [16]. This was 10% greater than that en-
countered in the Easotic® group (73.8% cure rate,
non-significant difference). The Easotic® results ob-
served in the study were consistent with efficacy results
previously published on the European Medicine Agency
(EMA) website (72.2% at D14) [18] and by Rigault
(74.7%) [19]. This difference between groups was mir-
rored by a non-significantly higher number of animals in
the Easotic® group requiring an additional therapy due to
relapse/failure before or on D21 (13 versus 9 animals in
the Aurizon® group). An increase in the cure rate be-
tween the end of treatment and at re-assessment 7 days
after completing treatment was observed in both groups.
Further improvement beyond the post-treatment exami-
nation was noted in the Aurizon® treated animals; this
finding was not replicated in the Easotic® group.
A sub-analysis of inclusion criteria based upon the
Aurizon® treatment duration selected by the clinician (7
or 14 days) showed that there were 2 populations of dogs
presenting with otitis externa: a population with a low
GCS which only required a 7 day course of therapy and a
second population with a higher GCS which necessitated
14 days of treatment. This confirmed that the duration of
treatment was influenced by the severity of disease at
initial presentation as opposed to the clinicians taking a
conservative approach and using the longest duration of
treatment available, regardless of the clinical picture. In
addition, it may indicate that in this study treatment dura-
tion was related to the clinical disease at inclusion and
not to differences in the progression of cases of otitis
externa which had a similar baseline. No variations were
observed for the LCS scores between animals who re-
ceived 7 or 14 days of treatment, but these scores were
already very high at the time of inclusion. Licensing re-
strictions (5 day treatment duration and instructions to
discard the medication 10 days after opening) prevented
a similar flexible dosing schedule being adapted for the
Easotic® group. Furthermore, studies have indicated that
a longer duration would not improve the cure rate [18]
which validates the licensed 5 day treatment duration.
The consequences of inadequate therapy in cases of otitis
externa are largely dependant upon the underlying aeti-
ology but can include relapse of clinical signs within
weeks of completing therapy, selection for antimicrobial
resistance in key pathogens or a progression to chronic
otitis externa.

E. GRANDEMANGE ET AL. 294
56.3%
81.2% 84.3%73.8%
48.8%
74.7%
0.0
10.0
20.0
30.0
40.0
50.0
60.0
70.0
80.0
90.0
100.0
Cure rate at the end of treatmentCure rate one week after the end of the
treatment Cure rate on D21
Percentages
Aurizon Easotic
Figure 1. Clinical progression of treatment groups relative to date of examination.
0
.3
.5
.8
1
1.3
1.5
1.8
2
2.3
D0D3D7D14 D21
AURIZON 7 days
EASOTIC 5 days
AURIZON 14 days
study day
General clinical score
Figure 2. Progression of the GCS relative to treatment group and duration of therapy.
Despite the lack of statistical significance, the differ-
ence observed between groups on D21 suggests that re-
assessment of cases 7 days after starting treatment and
subsequent adaptation of the treatment duration based
upon clinical response could improve therapeutic success
rate. Clinical cure is rarely possible unless the owner
complies with treatment protocols and this variable was
closely monitored by the investigators during the course
of this study. Boda [15], comparing Easotic® to another
ompound which required twice daily administration for c

E. GRANDEMANGE ET AL. 295
0
1
2
3
4
5
6
7
8
9
D0D3 D7 D14 D2 1
AURIZON 7 days
EASOTIC 5 days
AURIZON 14 days
study day
Local clinical score
Figure 3. Progression of the LCS relative to the treatment group and duration of therapy.
7 days, concluded that its simplified dosing regimen and
method of administration improved the owner compli-
ance. Another variable that must be considered is on-
going monitoring of otitis externa cases until the veteri-
narian decides that clinical cure has been achieved.
The results of this study suggest that when selecting an
appropriate therapy for otitis externa, clinicians should
consider not only ease of administration, but also effi-
cacy and the availability of extended durations of therapy
where needed to achieve clinical cure in the face of sig-
nificant clinical disease. Owner assessment of clinical
cure is unreliable as the glucocorticoid incorporated in
many ear preparations leads to resolution of easily ob-
servable markers of disease such as pain, pruritis, hyper-
plastic and proliferative. This may lead to an owner
electing to discontinue therapy before a true clinical cure
has been achieved.
A longer duration study (e.g. 6 months) would be an
interesting exercise and would enable the monitoring of
the frequency of relapses and/or the development of
chronic otitis externa.
No safety problem related to the investigated products
was reported throughout the study.
5. Conclusion
In conclusion, Aurizon® administered for 7 to 14 days
showed a non-significant tendency towards superior cli-
nical resolution than Easotic® administered for 5 days in
the treatment of acute otitis externa in the dog. The
treatment duration of Aurizon® prescribed by the inves-
tigator showed correlation with the severity of the gen-
eral clinical signs observed at inclusion.
6. Acknowledgements
This work was funded by Vétoquinol SA, Lure, France.
During the time of the study conduct, Erik Grandemange
and Frédérique Woehrlé were employed by Vétoquinol
SA, R&D Department, Lure, France. The authors ac-
knowledge the assistance of the staff at the clinics and
the laboratory involved and the cooperation of the own-
ers. The authors would like to thank Adrian Ward,
MRCVS for the English review of this article.
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