ManagingFeline Diabetes Mellitus
Fiona McClure, BVSc MVSc DACVIM

I doubt that anyone will ever tell you that managing diabetes mellitus (DM) isa "piece of cake". For a disease with a fairly straight forwardpathophysiology, it really does provide a challenge to all of us. Some newideas pertaining to managing this disease in our feline friends are interestingand in my experience have made treatment a lot easier and more successful. Inow recommend a low carbohydrate diet (Purina DM canned and dry, canned kittenfood) for diabetic cats unless they are moderately to severely azotemic (I usea cut-off of BUN ~ 80 mg/dl). I have found that the canned kitten food is thetastiest and have had less success with the dry DM compared with the canned DM(the cats seem to need more insulin). The diet should be meal-fed (BIDfeedings), not given free choice. When I meet a diabetic cat that is alreadyreceiving insulin and I change his diet to a low carbohydrate diet I definitelydecrease the insulin dose (best to halve it) to be sure that hypoglycemia doesnot occur

For a newly diagnosed feline DM patient I choose between insulin and an oralhypoglycemic agent. An oral hypoglycemic agent is more likely to work in anobese cat. The majority of the time I use insulin - certainly I do this ifthere is already neuropathy or if there is a history of ketosis or markedweight loss. I usually start with human recombinant insulin, usually NPH,although other veterinarians use Lente or Ultralente with success, proving thatthere is not really a "wrong" type to start with (although absorptionof ultralente can be problematic in some cats). I generally reserve beef PZIfor cases that are not doing well on the other types of insulin. Almost allcats need BID insulin, so I generally start with 1 unit BID and work upwardsfrom there. The site of insulin administration is varied to prevent fibrosis atone site (leading to subsequent poor absorption) and thick skinned/fatty areasof 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 (dose2.5 to 5 mg PO BID), but other choices are glimiperide (1-2 mg PO SID) andacarbose (12.5 mg PO BID). Glipizide and glimiperide work by promoting insulinrelease and increasing insulin receptor sensitivity. The side effects are notthat common but include anorexia, vomiting and liver disease. Giving the drugwith food helps to reduce side effects. Acarbose is another oral hypoglycemicdrug and although I haven't used it much, I have seen a few patients do quitewell with this medication. Acarbose works by impairing carbohydrate digestionand subsequently glucose absorption from the intestine. Side effects areflatulence and diarrhea. Don't use metformin in cats - it doesn't work well andit has severe side effects. I usually don't give insulin and oral hypoglycemicstogether.

I send the owner home with ketodiastix to monitor the urine several times aweek. Here I am looking for ketonuria (if present, the client should callimmediately) and the absence of glucose in the urine. If the latter occurs formore than several days in a row, then a dose reduction of insulin needs to beconsidered. I NEVER increase the insulin dose based on a urine glucose concentrationalone.

When starting insulin therapy in a newly diagnosed diabetic cat, I usuallymonitor the blood glucose (BG) several times per day after the first dose ofinsulin. I do this to make sure that hypoglycemia does not occur. I may do aglucose curve near the beginning of treat
ment mainly to assess the duration of effect of the insulin. This has to beinterpreted cautiously. We all know about the possible effect of stress on BGmeasurements in our patients. Another word of warning about glucose curvescomes from a research abstract at the ACVIM conference last year which showedthat a glucose curve can vary a huge amount on 2 consecutive days. In fact,treatment recommendations in the patients studied were different 65% of thetime depending on which curve was assessed. In the majority of patients, therecommendations were completely opposite (i.e. one curve suggested a decreasein dose was needed but the curve the following day suggested an increase in thedose was needed!).

In cats I try to rely on fructosamine concentrations and "spot" BGstaken 6-8 hours after the insulin dose. I do these 2 tests together every 3-4weeks or until control is adequate, then 2 to 4 times per year. Fructosaminereflects the overall BG in the last 2-3 weeks. I aim for fructosamine < 400mg/dl and a BG < 180 mg/dl. If fructosamine is ideal, but BG is high, thisprobably just reflects a stressed cat at venipuncture. If both are high, theinsulin dose is increased and if the BG and fructosamine are low, the insulindose is reduced. If the BG is low, but the fructosamine is high, I mightsuspect that owner compliance is not optimal at home (i.e. missing doses ofinsulin on some days but doing a great job on the day that the cat needs tovisit 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, markedweight fluctuations, excessive PU/PD and polyneuropathy, but I also want toavoid hypoglycemia. I think that it is very important to take a step back fromthe patient and base a lot of decisions on attitude, appetite, severity ofPU/PD and body weight rather than getting bogged down with laboratory data.

This article was originally printed in Spring2002 SouthPaws Newsletter

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