Open Journal of Veterinary Medicine, 2012, 2, 158-162
http://dx.doi.org/10.4236/ojvm.2012.23025 Published Online September 2012 (http://www.SciRP.org/journal/ojvm)
Tacrolimus for the Treatment of Inflammatory B owel
Disease in a Dog
Masashi Yuki*, Yosiaki Oota, Noriaki Nagata
Yuki Animal Hospital, Nagoya, Japan
Received July 12, 2012; revised August 18, 2012; accepted August 24, 2012
ABSTRACT
A 2-year-old intact female Toy poodle was referred with a 2-week history of diarrhea. Blood examination findings in-
dicated thrombocytosis, severe hypoproteinemia, and hypoalbuminemia; endoscopy revealed duodenal mucosal irregu-
larity and increased graininess. Based on these results and additional histopathological findings, we made a diagnosis of
protein-losing enteropathy caused by lymphocytic-plasmacytic enteritis with lymphangiectasia. The dog was initially
treated with prednisolone. Improvement was only observed with high-dose prednisolone; its dose could not be reduced
without relapse. When cyclosporin, methotrexate, and chlorambucil were combined with prednisolone, no further bene-
ficial effect was observed. When tacrolimus was combined with prednisolone, improvement was seen and the dose of
prednisolone could be reduced. Tacrolimus is both a calcineurin inhibitor and a multi-drug-resistant inhibitor, so it may
be an effective treatment choice for a dog refractory to standard inflammatory bowel disease treatment. This is the first
report of tacrolimus for the treatment of inflammatory bowel disease in dogs.
Keywords: Dog; Inflammatory Bowel Disease; Tacrolimus
1. Introduction
Canine inflammatory bowel disease (IBD) is a chronic,
immunologically mediated intestinal disorder resulting
from the complex interaction of environmental, genetic,
and immune factors [1]. Variations in the histologic ap-
pearance of the inflammation suggest that IBD is not a
single disease entity and the nomenclature merely re-
flects the predominant cell type present. Lymphocytic-
plasmacytic enteritis (LPE) is the most common form
reported, eosinophilic gastroenteritis is less common, and
granulomatous enteritis and neutrophilic infiltration are
rare in IBD [2]. Protein-losing enteropathy (PLE) may
occur secondary to conditions such as chronic inflamma-
tion in small intestinal diseases and is often caused by
intestinal lymphangiectasia following LPE [3].
The development of LPE is thought to originate as a
consequence of a deregulation of mucosal immunity in
predisposed animals. The immune-mediated basis of the
disease can be inferred by the response to the administra-
tion of immunosuppressive drugs [4]. Immunosuppres-
sive drugs such as prednisolone, azathioprine, chloram-
bucil, cyclosporin, and methotrexate are often used in the
treatment of this disorder [5], but achievement and main-
tenance of remission may be difficult using these agents.
Tacrolimus is an immunosuppressive macrolide iso-
lated from the fermentation broth of Streptomyces tsu-
kubaensis. It potently inhibits helper T lymphocyte acti-
vation [6]. Tacrolimus is the primary immunosuppressive
agent developed for organ transplantation. In recent re-
views of human refractory IBD, tacrolimus had therapeu-
tic efficacy, whereas prednisolone did not [7]. Recently,
in veterinary medicine, tacrolimus in ointment form has
begun to be used in the treatment of immune-mediated
skin diseases and keratoconjunctive disease [8-12].
In the present case, despite using a combination of
prednisolone and cyclosporin, methotrexate, and chlo-
rambucil, which is a potent, immunosuppressive agent, the
expected effect was not obtained. However, improve-
ment was confirmed when tacrolimus was substituted for
the trio of cyclosporin, methotrexate, and chlorambucil,
and rapid remission was achieved and maintained.
2. Case Description
A 3.5 kg, 2-year-old intact female Toy poodle was re-
ferred to our hospital with a 2-week history of diarrhea.
Upon physical examination, the dog had a temperature of
38.1˚C, a heart rate of 144 beats per minute, and a respi-
ratory rate of 30 breaths per minute; all were within
normal limits. The dog had a body condition score of 2
out of 5 and revealed a pendulous abdomen. Examina-
tions of the mucus membranes and heart sounds were
*Corresponding author.
C
opyright © 2012 SciRes. OJVM

M. YUKI ET AL. 159
normal.
Blood examination data at the time of admission re-
vealed thrombocytosis of 81.3 × 104/μL (reference range
20 to 50 × 104/μL), moderate hypocholesterolemia of 68
mg/dL (reference range 111 to 312 mg/dL), moderate
hypocalcemia of 7.9 mg/dL (reference range 9.3 to 12.1
mg/dL), severe hypoproteinemia of 3.2 g/dL (reference
range 5.0 to 7.2 g/dL), severe hypoalbuminemia of 1.3
g/dL (reference range 2.6 to 4.0 g/dL), and elevation of
C-reactive protein of 2.3 mg/dL (reference range 0 to 1.0
mg/dL). Total bile acid level was normal.
Fecal examination for internal parasites was negative.
Urinalysis was normal. Plain chest radiography was
normal. Plain abdominal radiography showed a loss of
intraabdominal detail and an abnormal colonic gas pat-
tern. Abdominal ultrasound showed ascitic fluid and in-
testinal wall thickness was normal. Ascitic fluid was
clear with a specific gravity of 1.004, total protein of 2.0
g/dL, and a few mononuclear cells that formed transu-
date.
Treatment with amoxicillin (Tatumi Kagaku Co., Ltd.,
Kanazawa, Japan) (10 mg/kg, periorally (PO), q 12 hr),
metronidazole (Shionogi & Co., Ltd., Osaka, Japan)
(12.5 mg/kg, PO, q 12 hr), and hypoallergenic Royal
Canine Veterinary Diet (Royal Canine Japan, Inc., Tokyo,
Japan) was begun to counter the possibility that the diar-
rhea was caused by bacteria, protozoa, or food allergy.
Furthermore, the antiparasitic drug combination of pra-
ziquantel/pyrantel pamoate/febantel (Bayer Yakuhin, Ltd.,
Osaka, Japan) was administered. However, the total protein
and albumin levels continued to remain low and diarrhea
resumed on the 20th day (Figure 1).
On the 21st day, an endoscopic examination was per-
formed for a definitive diagnosis. The gastric mucosa
was normal. The duodenal mucosa exhibited mucosal
irregularity and increased graininess. Histopathological
review of biopsy specimens confirmed normal gastric
mucosa and duodenal mucosal inflammation consistent
with moderate to severe lymphocytic-plasmacytic infil-
tration and hydropic degeneration. The lymphatics of
these areas were slightly dilated. A diagnosis of PLE
secondary to LPE was made at this point.
Administration of prednisolone (Shionogi & Co., Ltd.,
Osaka, Japan) (1 mg/kg, PO, q 12 hr) was begun. In-
creases in the total protein and albumin levels were con-
firmed and diarrhea improved in 1 week. On the 38th day,
however, when prednisolone was reduced to 0.75 mg/kg
q 12 hr, total protein and albumin levels decreased (Fig-
ure 1) and alanine aminotransferase level increased.
Treatment with cyclosporin (Novartis Pharma K. K.,
Tokyo, Japan) (5 mg/kg, PO, q 24 hr) was begun to en-
able the tapering of prednisolone. Prednisolone was re-
duced gradually again, but the total protein and albumin
levels remained stable and no diarrhea was observed. On
the 130th day, prednisolone was reduced to 0.15 mg/kg q
12 hr. Total protein and albumin levels decreased and
diarrhea returned (Figure 1). Prednisolone was increased
to 0.5 mg/kg twice a day again, but no increase in total
protein and albumin levels was observed.
On the 144th day, treatment with prednisolone and cyc
A
TP, Total Protein; ALB, Albumin
Figure 1. Clinical course of treatment with prednisolone, cyclosporin, methotrexate, chlorambucil and tacrolimus in a dog
with protein-losing enteropathy caused by lymphocytic-plasmacytic enteritis with lymphangiectasia.

M. YUKI ET AL.
160
losporine with methotrexate (Wyeth, Tokyo, Japan) (0.5
mg/kg, intramuscularly, once a week) was started. Diar-
rhea improved, although no increases in total protein and
albumin levels were observed. Vomiting, which is a side
effect of methotrexate, was observed. On the 151st day,
cyclosporin was discontinued because it did not produce
sufficient effect and its cost was a problem. On the 158th
day, chlorambucil (Glaxo Smith Kline, Bern, Switzerland)
(0.35 mg/kg, PO, q 24 hr) was substituted for meth-
otrexate. Vomiting, which is a side effect of chloram-
bucil, and diarrhea were observed.
On the 178th day, a severe decrease in total protein
and albumin levels was seen, tacrolimus (Astellas Pharma
Inc., Tokyo, Japan) (0.13 mg/kg, PO, q 12 hr) was sub-
stituted for chlorambucil, and prednisolone was increased
to 1 mg/kg q 12 hr again. The increase in the total protein
and albumin levels was confirmed and diarrhea improved
after 1 week (Figur e 1). On the 194th day, moreover, pred-
nisolone was discontinued 4 days into the course due to a
bite wound, no decrease in total protein and albumin lev-
els was seen, and a temporary increase of globulin was
observed (Figure 1). On the 219th day, prednisolone
dosing was gradually reduced to a low-dose level (0.15
mg/kg, PO, q 12 hr) while maintaining an increase of
total protein and albumin levels. In addition, the trough
level of the tacrolimus at this point was below 2 ng/mL
(Mitsubishi Chemical Medience Corporation, Tokyo,
Japan). On the 290th day, the total protein and albumin
levels reached the reference ranges and it was possible to
get a complete remission (Figure 1).
Tacrolimus dosing was gradually reduced to 0.065
mg/kg every other day from the 401st day to the 467th
day. However, decreases in total protein and albumin
levels were observed clearly (Figure 1). On the 467th
day, tacrolimus dosing was increased again to 0.065
mg/kg q 24 hr. On the 509th day, total protein and albu-
min levels improved into the reference ranges. On the
538th day, tacrolimus dosing was reduced to every other
day again to relieve the burden of its cost. However, a
decrease of total protein and albumin levels was ob-
served and tacrolimus was again increased to q 24 hr
(Figure 1). More than 800 days have passed since tac-
rolimus treatment was begun; no adverse effect has been
observed and treatment progress is good.
3. Discussion
The mechanism of action of tacrolimus is similar to that of
cyclosporin, even though their chemical structures differ
greatly [6]. Tacrolimus binds to immunophilins, which are
cytoplasmic binding proteins. While tacrolimus binds to
immunophilins called FK-binding proteins (FKBPs), cyc-
losporin binds to immunophilins called cyclophilins. The
immunophilin-drug complex binds competitively to and
inhibits calcineurin, a phosphatase whose activity is de-
pendent on its being bound to calcium and calmodulin.
Inhibition of calcineurin is believed to mediate the im-
munosuppressive activity of both tacrolimus and cyc-
losporine [6]. Tacrolimus has been shown to inhibit the
transcription of the early activation genes for cytokines
such as interleukin 2, tumor necrosis factor α, and interferon
γ in T cells [7]. Although its mode of action is similar
to that of cyclosporin, the immunosuppressive effect of
tacrolimus is 30 - 100 times greater in vitro and 10 - 20
times greater in vivo than that of cyclosporin [7].
In recent reviews of human refractory IBD, the cal-
cineurin inhibitor tacrolimus had therapeutic efficacy [7].
In recent reviews of veterinary medicine, the calcineurin
inhibitor cyclosporin was also effective in dogs with re-
fractory IBD. The anti-inflammatory effect of cyclosporin
in human and dogs IBD are belived to be due to suppres-
sion of activated T cells infiltrating the mucosa [13].
In this case, it was insufficient, but the use of tac-
rolimus with the same mechanism was tried because
some effect of cyclosporin was seen. In human IBD, tac-
rolimus is used at a rate of 0.025 mg/kg given orally
every 12 hours, with a trough level of 5 - 15 ng/mL [7].
In dogs, a high dose of 0.4 - 2.0 mg/kg seems to be
needed to get this trough level [14,15]. However, severe
adverse effects including body weight loss and pneumo-
nia may result from the high dose of 0.4 - 2.0 mg/kg [15].
Clinically, the therapeutic dose of tacrolimus for dogs
has not been determined, so we used as a reference the
dosage in human organ transplantation [6].
The trough level in this case was below 2 ng/mL, low-
er than the recommended therapeutic dose for human
IBD. However, effectiveness was observed. All cytokine
production was inhibited completely at a blood level of 1
ng/mL in a basic study of tacrolimus in humans; the 50%
inhibitory concentration was 0.02 - 0.11 ng/mL and an
inhibitory effect was indicated by a low concentration
[16]. The trough level was not recorded in a report on
tacrolimus for the treatment of sterile panniculitis in a
dog, but the effect was observed at a low dose of 0.06
mg/kg/day [17]. Therefore, there is a possibility that even
a low dose and a low trough level can be effective in
dogs. However, because in this case, tacrolimus was
given every other day, the resulting lower total protein
and albumin levels indicated the need for daily admini-
stration.
Recently, the high expression of p-glycoprotein was
confirmed in lymphocytes from duodenum mucous mem-
brane lamina propria after treatment with prednisolone in
dogs with IBD and possible drug resistance by p-glyco-
protein was suggested [18]. Presently, p-glycoprotein and
cytochrome P-450 3A4, 3A5 manifested in the small
intestine and liver appear to be cooperatively functioning
as the cause of the absorption barrier of tacrolimus [19].
On the other hand, cyclosporin and tacrolimus can block

M. YUKI ET AL. 161
the p-glycoprotein of resistant cells and are viewed as
multi-drug-resistant inhibitors that obstruct the multi-
drug resistance function [20]. It is thought that calcineurin
inhibitors have different actions and that these actions are
manifested early at low concentrations [20,21]. An insuf-
ficient effect was observed from the use of cyclosporin in
this case. However, with tacrolimus, an immediate effect
was observed with its low dose, so its multi-drug resis-
tant inhibitor actions may be involved in this case.
In humans, the most common adverse effects seen
with tacrolimus include headache, tremors, insomnia,
hyperesthesia, and musculoskeletal complaints [6]. In
this case, low-dose tacrolimus has been given for more
than 2 years, but no adverse effect has been observed.
However, attention will be necessary for the sign because
adverse effect include body weight loss and pneumonia
in the dogs [15].
In conclusion, because tacrolimus is both a calcineurin
inhibitor and a multi-drug-resistant inhibitor, it may be
an effective treatment choice for dogs refractory to IBD
treatment. More studies about the effect on IBD and the
clinical dose of tacrolimus in dogs are needed. To the
best of our knowledge, this is the first report of tac-
rolimus for the treatment of IBD in dogs.
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