I have a 14-year-old female spayed DSH feline weighing 5.4 kg, who was diagnosed with diabetes one year ago. To date, she has been receiving 4 IU of PZI (ProZinc) twice daily, and the owners have been very good about keeping her on a diet of high protein/low carbohydrate canned food only.

The owners would like to try switching from the insulin to an oral hypoglycemic agent (glipizide or glyburide). They travel a lot and have difficulty finding someone to look after her, and even having to board her at the clinic is a problem because she is very fractious and difficult to catch and give injections too. The owners themselves can manage just fine with the insulin injections, but no one else can.

Recently, I did some blood work on her and she is doing great. She is no longer polydipsic or polyuric, her serum glucose was normal at 122 mg/dl, and her serum fructosamine was 275 µmol/l (reference range 150-350 µmol/l).

My questions are the following:


- How do I properly transition her to the glipizide or glyburide if we decide to go that route?
- Does this cat even need to continue with insulin or oral glucose products, or can I control her on diet therapy alone at this point?
- Could this cat be going into diabetes remission?

My Response:

The lack of clinical signs and normal fructosamine certainly indicates good diabetes control, and it is possible that the cat is going into remission. Clinical remission is actually not infreqent in cats with well-controlled diabetes mellitus (1).

However, remission, when it does occur, generally develops earlier than a year (generally within the first 3 months of starting insulin therapy) so it's less likely that a cat treated with insulin for a year would be in remission. In addition, when most cats are going into remission, they're generally not normal on 4 units BID — that would be an overdose in most cats in remission. The more typical scenario in a cat going into remission is that their glucose values are dropping too low even on 1 unit BID.

That all said, diabetic remission is possible at any time and it's still possible that your cat is going into remission.

Ideally, the first step in judging remission would be for you would do a complete glucose curve to see if the blood glucose concentrations remain normal through out the day. The finding of a single "normal" blood sugar really doesn't tell you very much at all.

I understand that hospitalizing this fractious cat for a glucose curve would probably not be a pleasant experience for either you or the cat; more importantly, the "stress" would likely make the results meaningless anyway. Can the owners do home glucose monitoring? If so, that would be extremely helpful. Can they, at the very least, measure urine glucose at home?

In the end, how you decide whether the diabetes is going into remission or not is to slowly taper down the insulin dosage by 0.5 U decrements (e.g., start by decreasing from 4 U, BID to 3.5 U, BID). If the blood and/or urine glucose concentration remain normal after a week, then the insulin taper can continue until the insulin can hopefully be discontinued.

The chance of an oral hypoglycemic agent (glibizide or glyburide) working is very small. I personally think it's easier to give insulin to a fractious cat than to give a pill, especially in the hospital or in a kennel.

Remember, oral hypoglycemic agents act by stimulating insulin secretion from the pancreatic islet cells (2). In a cat with borderline diabetes that is going into remission, changing from insulin therapy to one of these drugs may actually be the worst thing to do.

Use of these oral hypoglycemic drugs, by overstimulating any remaining insulin secretion, my actually lead to the final "burn out" of insulin secretion and result in permanent diabetes (2).

Reference:

1. Zini E, Hafner M, Osto M, et al. Predictors of clinical remission in cats with diabetes mellitus. Journal of Veterinary Internal Medicine 2010;24:1314-132
2. Hoenig M, Hall G, Ferguson D, et al. A feline model of experimentally induced islet amyloidosis. American Journal of Pathology 2000; 157:2143-50

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