(Diabetes Mellitus--Continued from page 1)

For a newly diagnosed feline DM patient I choose between insulin and an oral hypoglycemic agent. An oral hypoglycemic agent is more likely to work in an obese cat. The majority of the time I use insulin - certainly I do this if there is already neuropathy or if there is a history of ketosis or marked weight loss.  I usually start with human recombinant insulin, usually NPH, although other veterinarians use Lente or Ultralente with success, proving that there is not really a "wrong" type to start with (although absorption of ultralente can be problematic in some cats). I generally reserve beef PZI for cases that are not doing well on the other types of insulin.  Almost all cats need BID insulin, so I generally start with 1 unit BID and work upwards from there. The site of insulin administration is varied to prevent fibrosis at one site (leading to subsequent poor absorption) and thick skinned/fatty areas of the body are avoided. A new bottle should be purchased every 2-3 months.

If I decide to use an oral hypoglycemic agent, I usually use glipizide (dose 2.5 to 5 mg PO BID), but other choices are glimiperide (1-2 mg PO SID) and acarbose (12.5 mg PO BID). Glipizide and glimiperide work by promoting insulin release and increasing insulin receptor sensitivity. The side effects are not that common but include anorexia, vomiting and liver disease. Giving the drug with food helps to reduce side effects. Acarbose is another oral hypoglycemic drug and although I haven't used it much, I have seen a few patients do quite well with this medication. Acarbose works by impairing carbohydrate digestion and subsequently glucose absorption from the intestine. Side effects are flatulence and diarrhea. Don't use metformin in cats - it doesn't work well and it has severe side effects. I usually don't give insulin and oral hypoglycemics together.

I send the owner home with ketodiastix to monitor the urine several times a week. Here I am looking for ketonuria (if present, the client should call immediately) and the absence of glucose in the urine. If the latter occurs for more than several days in a row, then a dose reduction of insulin needs to be considered. I NEVER increase the insulin dose based on a urine glucose concentration alone.

When starting insulin therapy in a newly diagnosed diabetic cat, I usually monitor the blood glucose (BG) several times per day after the first dose of insulin.  I do this to make sure that hypoglycemia does not occur. I may do a glucose curve near the beginning of treat

ment mainly to assess the duration of effect of the insulin.  This has to be interpreted cautiously. We all know about the possible effect of stress on BG measurements in our patients.  Another word of warning about glucose curves comes from a research abstract at the ACVIM conference last year which showed that a glucose curve can vary a huge amount on 2 consecutive days. In fact, treatment recommendations in the patients studied were different 65% of the time depending on which curve was assessed.  In the majority of patients, the recommendations were completely opposite (i.e. one curve suggested a decrease in dose was needed but the curve the following day suggested an increase in the dose was needed!).

In cats I try to rely on fructosamine concentrations and "spot" BGs taken 6-8 hours after the insulin dose. I do these 2 tests together every 3-4 weeks or  until control is adequate, then 2 to 4 times per year. Fructosamine reflects the overall BG in the last 2-3 weeks. I aim for fructosamine < 400 mg/dl and a BG < 180 mg/dl. If fructosamine is ideal, but BG is high, this probably just reflects a stressed cat at venipuncture. If both are high, the insulin dose is increased and if the BG and fructosamine are low, the insulin dose is reduced. If the BG is low, but the fructosamine is high, I might suspect that owner compliance is not optimal at home (i.e. missing doses of insulin on some days but doing a great job on the day that the cat needs to visit the vet).

Finally, one of the things that I have learned about feline diabetics is to not "over-control" them. Definitely I want to avoid ketoacidosis, marked weight fluctuations, excessive PU/PD and polyneuropathy, but I also want to avoid hypoglycemia. I think that it is very important to take a step back from the patient and base a lot of decisions on attitude, appetite, severity of PU/PD and body weight rather than getting bogged down with laboratory data.