Methylprednisolone acetate (Depo-Medrol, Upjohn) can be used as sole treatment for cats with mild to moderate IBD or as adjunctive
therapy when oral prednisone and/or metronidazole are used as the primary treatment and flare-ups of clinical signs occur.
Consistent control of clinical signs in cats with moderate to severe IBD is more difficult to maintain when methylprednisolone
acetate is used alone, however. It is recommended that sole use of methylprednisolone acetate be reserved for situations
in which the owner is unable to consistently administer tablet or liquid prednisolone preparations. Initially 20 mg is given
subcutaneously or intramuscularly and is repeated at 2-week intervals for 2 to 3 doses. Injections are then given every 2
to 4 weeks or as needed for control.
If remission cannot be maintained with use of corticosteroids and metronidazole then azathioprine (Imuran) should be used.
Azathioprine is an immunosuppressive drug with a nonspecific effect. Replication of rapidly dividing cells, including immunoblasts,
is inhibited. Azathioprine is usually used in cats only when the previously discussed therapeutic measures fail to control
the disease. The most important side effect of azathioprine in cats is bone marrow suppression. I use a maximum starting
dose in cats of 0.3 mg/kg (0.15 mg/lb) once every other day. At this low dose side effects are extremely uncommon. Alternatively
if clinical signs of IBD do not resolve on the initial azathioprine dose the dose can be increased slightly if there is no
evidence of bone marrow suppression. Because of a lag effect, beneficial therapeutic results from azathioprine often are
not apparent until 2 to 3 weeks after treatment is started. Azathioprine is generally used for 3 to 9 months in cats. A
majority of cats with IBD do not require azathioprine treatment.
A complete blood count should be run to monitor for anemia and leukopenia at 3 to 4 week intervals for the first 2 months
and then once monthly. Significant side effects are most often identified during the first 3 to 6 weeks of treatment with
azathioprine. There is usually no physical evidence of early azathioprine toxicity in cats. Mild leukopenia (e.g., 3000
- 4000 cells/mm) is usually the first abnormality that is identified. Azathioprine is currently only available as 50 mg tablets.
The low dosage used in cats requires that the tablet be broken into small fragments (i.e., 1/30 - 1/50 tablet depending on
body weight). Since this is a very inaccurate and potentially dangerous way of administering azathioprine to cats, this drug
must be administered in suspension form.
A suspension preparation can be made by a compounding pharmacy service. A major advantage of administering azathioprine in
this manner is that any required increase in dosage can be done very accurately. If azathioprine is well tolerated and there
has been inadequate clinical improvement the dosage can be increased form 0.15 mg/lb to 0.2 to 0.25 mg/lb once every 48 hours.
Another immunosuppressive drug that is used in some cats with severe IBD is chlorambucil (Leukeran). Some clinicians use
chlorambucil as an alternative to azathioprine (they are not used in conjunction). Chlorambucil is an alkylating agent.
Alkylating agents alter DNA synthesis and inhibit rapidly proliferating cells. Chlorambucil is administered initially at
0.01 to 0.2 mg/kg/day in conjunction with prednisolone at 2.2 mg/kg/day. The small pill size of chlorambucil (2 mg) allows
for easy dosing. Most cats receive one-half tablet (1 mg) per day. Various dosage schedules for cats have been published.
An alternate schedule is 0.15 to 0.3 mg/kg every 72 hours. Toxicities are uncommon in cats but may include anorexia, vomiting,
and diarrhea, but these problems generally resolve rapidly when chlorambucil is reduced from daily to every other day administration.
Bone marrow suppression is possible but uncommon, and is mild and rapidly reversible when it does occur. Once the desired
clinical response is achieved, chlorambucil is gradually tapered over several months while prednisolone is continued as the
primary maintenance drug.
Cobalamin therapy in cats: Significant tissue level cobalamin deficiency is present in some animals with GI disease. This is usually secondary to reduced
cobalamin absorptive capacity. Therapy involves administering injectable cobalamin at the following schedule for cats: 250
ug subcutaneously once a week for 6 weeks, then every 2 weeks for the next 6 doses, then dose monthly. Most generic cobalamin
preparations contain 1 mg/ml (1000 ug/ml). It is important to note that multi-vitamin and B-complex injectable formulations
contain significantly lower concentrations of cobalamin and they also cause pain when injected. Therefore, it is recommended
that these preparations not be used for cobalamin supplementation. Unless the intestinal disease is totally resolved, long-term
and perhaps lifelong supplementation with cobalamin may be necessary. The frequency of injections on a long-term basis is
determined by regular measurement of serum cobalamin concentration.
Because dietary allergens may play a role in the cause if IBD, specific dietary therapy may be beneficial. Often, moderate
to severe degrees of IBD are either temporarily responsive or only minimally responsive to careful dietary manipulations.
However, long term control of IBD with as minimal a drug administration schedule as possible may be aided by specific dietary
management. This should be started as soon as a diagnosis is made and continued as drug therapy is decreased later. Chicken,
duck, lamb, or venison based diets are often tried initially. A gradual change to commercial diets that are low in additives
and that are formulated with chicken or lamb as their primary ingredient is then attempted. Diets such as IVD Select Care
Neutral or IVD Limited Ingredient Diets, Iams Feline, Hill's Prescription Diet c/d or w/d, or Waltham select protein diets
are generally recommended.
Poor responses to treatment of cats with IBD usually result from:
1. Inadequate initial or long-term maintenance corticosteroid dosage (and consider using prednisolone rather than prednisone).
2. Failure to use ancillary medications (metronidazole, azathioprine, chlorambucil) in cases where disease is moderate to
3. Failure to recognize and treat a concurrent condition (e.g., gastric hypomotility disorder that may either be secondary
to IBD or idiopathic in nature, hyperthyroidism, parasitism [e.g., Giardia, Cryptosporidium], Clostridium
4. Treatment for only small intestinal inflammatory disease when colitis is present as well. Some cats with concurrent IBD
and colitis may show minimal or no clinical signs of colitis.
5. Failure to recognize and treat low body cobalamin levels (measure serum cobalamin).
6. Failure to identify an effective diet.
7. Poor client compliance