Other immunosuppressive agents, such as azathioprine, chlorambucil or cyclophosphamide, at the usual dosages, are used alone
or in combination with corticosteroids. When used in combination, they may decrease the required dosage of corticosteroids
and the associated side effects or allow the dogs to be weaned off corticosteroids as soon as possible. Moreover, these drugs
are also used for cases of steroid-refractory canine IBD. They may have a delayed onset of action (weeks to months until maximal
If the IBD is limited to the large bowel, compound molecules containing mesa-lamine (5-ASA) such as sulfa-salazine (initially
10-25 mg/kg orally TID for six weeks, then taper down) or olsalazine (initially 5-10 mg/kg orally TID, then reduce gradually)
have proven beneficial effects on the colonic mucosa. Keratoconjunctivitis sicca is a well-known complication in dogs treated
with either of these two drugs.
Cyclosporin A (cyA) (5 mg/kg orally once daily for a total of 10 weeks) may be a valid alternative for canine IBD. The cellular
infiltrate in canine chronic idiopathic enteropathies mainly consists of lymphocytes and plasma cells in the lamina propria.
The anti-inflammatory effect of cyA in IBD is thought to be due to its action on T-cells that infiltrate the mucosa. CyA binds
intracellularly to calmodulin, which reduces the release of calcium from the endoplasmic reticulum, thereby inhibiting further
down-stream signaling, and finally inhibiting the expression of IL-2. Because IL-2 is necessary for the survival of T-cells
for longer than 24-48 hours, it is hypo-thesized that cyA decreases the number of infiltrating T-cells in the mucosa of the
dogs, thereby reducing the amount of pro-inflammatory cytokines, and finally, the clinical signs of the disease. Reported
side effects are vomiting, partial anorexia, gingival ulceration and alopecia followed by hypertrichosis.
Probiotics are living non-pathogenic micro-organisms that may exert beneficial effects on the immune system. In an ex-vivo
culture system of duodenal biopsies from dogs with IBD, addition of three strains of Lactobacilli enhanced the expression
of the regulatory cytokine IL-10. Based on these results, the use of such probiotics in vivo in dogs with IBD may be of benefit
to decrease intestinal inflammation.
What's your question?
Send your pediatric/geriatric related questions to: Pediatric/Geriatric Protocol, DVM Newsmagazine, 7500 Old Oak Blvd., Cleveland, OH 44130. Your questions will be answered by Dr. Hoskins in upcoming columns.