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466 Small Animal/Exotics Compendium June 2002<br />
Corticosteroids<br />
Prednisone is a corticosteroid that is a rapid and potent<br />
suppressor of the <strong>ce</strong>ll-mediated response and the humoral<br />
response. Corticosteroids are considered the treatment of<br />
choi<strong>ce</strong> in cases of moderate to severe IBD (lymphocytic–plasmacytic)<br />
and are usually effective when metronidazole is not.<br />
Side effects include gastric, duodenal, or colonic ul<strong>ce</strong>ration<br />
and iatrogenic hyperadrenocorticism. Dexamethasone should<br />
be avoided because of its prolonged effects on the hypothalamic–pituitary<br />
axis. Prednisone can be given daily and then<br />
tapered to alternate-day maintenan<strong>ce</strong> therapy when clinical<br />
signs resolve. Patients that have severe side effects on alternate-day<br />
therapy can be given an alternative therapy alone or<br />
in <strong>com</strong>bination with lowered doses of prednisone. Budesonide,<br />
a corticosteroid that is given orally and has topical<br />
effects in the small and large bowel with minimal systemic<br />
absorption, has been used suc<strong>ce</strong>ssfully in humans with ul<strong>ce</strong>rative<br />
colitis. 39 It is currently being investigated for its use in<br />
dogs with IBD. Azathioprine, a suppressor of the antigenindu<strong>ce</strong>d<br />
lymphocyte transformation, is a <strong>com</strong>monly used<br />
alternative. Azathioprine can be given alone or in <strong>com</strong>bination<br />
with lower doses of prednisone. It is usually given daily<br />
for 2 weeks and then tapered to every other day. Side effects<br />
include anorexia, vomiting, diarrhea, and bone marrow suppression.<br />
Mild bone marrow suppression is <strong>com</strong>mon and not<br />
of great con<strong>ce</strong>rn. Although rare, severe suppression occurs<br />
more <strong>com</strong>monly in cats than in dogs and is most often seen<br />
early in the treatment protocol. 36 Pancreatitis and hepatotoxicity<br />
have also been reported. 36 Patient monitoring with routine<br />
<strong>com</strong>plete blood <strong>ce</strong>ll count analysis is indicated.<br />
Chemotherapeutic Agents<br />
Patients with severe and refractory IBD may respond to<br />
cyclophosphamide. Cyclophosphamide is a chemotherapeutic<br />
agent that is a potent immunosuppressor. 36 Side effects include<br />
vomiting, diarrhea, sterile hemorrhagic cystitis (in dogs), and<br />
bone marrow suppression. It is given daily for 4 consecutive<br />
days and then discontinued for 3 days each week, making this<br />
drug easier than azathioprine to administer to cats. The patient<br />
must be monitored closely with routine <strong>com</strong>plete blood <strong>ce</strong>ll<br />
count analyses. Chlorambucil is an oral chemotherapeutic drug<br />
with cytotoxic effects similar to those of cyclophosphamide<br />
(although not as potent) but may be helpful in some refractory<br />
cases of IBD. 36 Side effects of bone marrow suppression are<br />
minimal when using chlorambucil <strong>com</strong>pared with cyclophosphamide,<br />
and GI signs are usually eliminated by alternate-day<br />
dosing. Cyclosporine, a T-<strong>ce</strong>ll suppressor drug available in oral<br />
preparation, has not been studied in dogs and cats with IBD<br />
but has been shown to be an effective treatment in humans<br />
with severe, unresponsive IBD. 36 Although it is very expensive,<br />
cyclosporine has been used to treat other immune-mediated<br />
diseases in dogs and cats and could be considered in severe cases.<br />
Side effects include vomiting, diarrhea, pancreatitis, and bone
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